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[PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS

Laurent Dufour posted 1 patch 4 years, 3 months ago 
arch/powerpc/kernel/entry_64.S | 18 ++++++------------
arch/powerpc/kernel/rtas.c     |  5 +++++
2 files changed, 11 insertions(+), 12 deletions(-)
[PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS
Posted by Laurent Dufour 4 years, 3 months ago 
RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32bits
mode (MSR[SF] unset).

The change in MSR is done in enter_rtas() in a relatively complex way,
since the MSR value could be hardcoded.

Furthermore, a panic has been reported when hitting the watchdog interrupt
while running in RTAS, this leads to the following stack trace:

[69244.027433][   C24] watchdog: CPU 24 Hard LOCKUP
[69244.027442][   C24] watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago)
[69244.027451][   C24] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
[69244.027555][   C24]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
[69244.027587][   C24] Supported: No, Unreleased kernel
[69244.027600][   C24] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
[69244.027609][   C24] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
[69244.027612][   C24] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
[69244.027615][   C24] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
[69244.027625][   C24] CFAR: 000000000000011c IRQMASK: 1
[69244.027625][   C24] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
[69244.027625][   C24] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
[69244.027625][   C24] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
[69244.027625][   C24] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
[69244.027625][   C24] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
[69244.027625][   C24] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
[69244.027625][   C24] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
[69244.027625][   C24] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
[69244.027663][   C24] NIP [000000001fb41050] 0x1fb41050
[69244.027696][   C24] LR [000000001fb4104c] 0x1fb4104c
[69244.027699][   C24] Call Trace:
[69244.027701][   C24] Instruction dump:
[69244.027723][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.027728][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.027762][T87504] Oops: Unrecoverable System Reset, sig: 6 [#1]
[69244.028044][T87504] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[69244.028089][T87504] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
[69244.028171][T87504]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
[69244.028307][T87504] Supported: No, Unreleased kernel
[69244.028385][T87504] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
[69244.028408][T87504] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
[69244.028418][T87504] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
[69244.028429][T87504] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
[69244.028444][T87504] CFAR: 000000000000011c IRQMASK: 1
[69244.028444][T87504] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
[69244.028444][T87504] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
[69244.028444][T87504] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
[69244.028444][T87504] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
[69244.028444][T87504] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
[69244.028444][T87504] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
[69244.028444][T87504] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
[69244.028444][T87504] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
[69244.028534][T87504] NIP [000000001fb41050] 0x1fb41050
[69244.028543][T87504] LR [000000001fb4104c] 0x1fb4104c
[69244.028549][T87504] Call Trace:
[69244.028554][T87504] Instruction dump:
[69244.028561][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.028575][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.028607][T87504] ---[ end trace 3ddec07f638c34a2 ]---

This happens because MSR[RI] is unset when entering RTAS but there is no
valid reason to not set it here.

Fixing this by reviewing the way MSR is compute before calling RTAS. Now a
hardcoded value meaning real mode, 32 bits and Recoverable Interrupt is
loaded.

In addition a check is added in do_enter_rtas() to detect calls made with
MSR[RI] unset, as we are forcing it on later.

Cc: stable@vger.kernel.org
Suggested-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
 arch/powerpc/kernel/entry_64.S | 18 ++++++------------
 arch/powerpc/kernel/rtas.c     |  5 +++++
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9581906b5ee9..fbc8dfe7da9f 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -330,22 +330,16 @@ _GLOBAL(enter_rtas)
 	clrldi	r4,r4,2			/* convert to realmode address */
        	mtlr	r4
 
-	li	r0,0
-	ori	r0,r0,MSR_EE|MSR_SE|MSR_BE|MSR_RI
-	andc	r0,r6,r0
-	
-        li      r9,1
-        rldicr  r9,r9,MSR_SF_LG,(63-MSR_SF_LG)
-	ori	r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
-	andc	r6,r0,r9
-
 __enter_rtas:
-	sync				/* disable interrupts so SRR0/1 */
-	mtmsrd	r0			/* don't get trashed */
-
 	LOAD_REG_ADDR(r4, rtas)
 	ld	r5,RTASENTRY(r4)	/* get the rtas->entry value */
 	ld	r4,RTASBASE(r4)		/* get the rtas->base value */
+
+	/* RTAS runs in 32bits real mode but we may hit watchdog irq */
+	LOAD_REG_IMMEDIATE(r6, MSR_ME|MSR_RI)
+
+	li      r0,0
+	mtmsrd  r0,1                    /* disable RI before using SRR0/1 */
 	
 	mtspr	SPRN_SRR0,r5
 	mtspr	SPRN_SRR1,r6
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 1f42aabbbab3..d7775b8c8853 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -49,6 +49,11 @@ void enter_rtas(unsigned long);
 
 static inline void do_enter_rtas(unsigned long args)
 {
+	unsigned long msr;
+
+	msr = mfmsr();
+	BUG_ON(!(msr & MSR_RI));
+
 	enter_rtas(args);
 
 	srr_regs_clobbered(); /* rtas uses SRRs, invalidate */
-- 
2.35.1
Re: [PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS
Posted by Nicholas Piggin 4 years, 2 months ago 
Excerpts from Laurent Dufour's message of March 17, 2022 9:06 pm:
> RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32bits
> mode (MSR[SF] unset).
> 
> The change in MSR is done in enter_rtas() in a relatively complex way,
> since the MSR value could be hardcoded.
> 
> Furthermore, a panic has been reported when hitting the watchdog interrupt
> while running in RTAS, this leads to the following stack trace:
> 
> [69244.027433][   C24] watchdog: CPU 24 Hard LOCKUP
> [69244.027442][   C24] watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago)
> [69244.027451][   C24] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
> [69244.027555][   C24]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
> [69244.027587][   C24] Supported: No, Unreleased kernel
> [69244.027600][   C24] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
> [69244.027609][   C24] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
> [69244.027612][   C24] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
> [69244.027615][   C24] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
> [69244.027625][   C24] CFAR: 000000000000011c IRQMASK: 1
> [69244.027625][   C24] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
> [69244.027625][   C24] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
> [69244.027625][   C24] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
> [69244.027625][   C24] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
> [69244.027625][   C24] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
> [69244.027625][   C24] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
> [69244.027625][   C24] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
> [69244.027625][   C24] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
> [69244.027663][   C24] NIP [000000001fb41050] 0x1fb41050
> [69244.027696][   C24] LR [000000001fb4104c] 0x1fb4104c
> [69244.027699][   C24] Call Trace:
> [69244.027701][   C24] Instruction dump:
> [69244.027723][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> [69244.027728][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> [69244.027762][T87504] Oops: Unrecoverable System Reset, sig: 6 [#1]
> [69244.028044][T87504] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> [69244.028089][T87504] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
> [69244.028171][T87504]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
> [69244.028307][T87504] Supported: No, Unreleased kernel
> [69244.028385][T87504] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
> [69244.028408][T87504] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
> [69244.028418][T87504] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
> [69244.028429][T87504] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
> [69244.028444][T87504] CFAR: 000000000000011c IRQMASK: 1
> [69244.028444][T87504] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
> [69244.028444][T87504] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
> [69244.028444][T87504] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
> [69244.028444][T87504] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
> [69244.028444][T87504] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
> [69244.028444][T87504] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
> [69244.028444][T87504] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
> [69244.028444][T87504] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
> [69244.028534][T87504] NIP [000000001fb41050] 0x1fb41050
> [69244.028543][T87504] LR [000000001fb4104c] 0x1fb4104c
> [69244.028549][T87504] Call Trace:
> [69244.028554][T87504] Instruction dump:
> [69244.028561][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> [69244.028575][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> [69244.028607][T87504] ---[ end trace 3ddec07f638c34a2 ]---
> 
> This happens because MSR[RI] is unset when entering RTAS but there is no
> valid reason to not set it here.
> 
> Fixing this by reviewing the way MSR is compute before calling RTAS. Now a
> hardcoded value meaning real mode, 32 bits and Recoverable Interrupt is
> loaded.
> 
> In addition a check is added in do_enter_rtas() to detect calls made with
> MSR[RI] unset, as we are forcing it on later.

This looks okay to me, I would just adjust the comment about watchdog
irq. It's more like NMI (SRESET or MCE), watchdog irq could be confusing 
for the soft-NMI timer.

Otherwise I think it's okay.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Cc: stable@vger.kernel.org
> Suggested-by: Nicholas Piggin <npiggin@gmail.com>
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> ---
>  arch/powerpc/kernel/entry_64.S | 18 ++++++------------
>  arch/powerpc/kernel/rtas.c     |  5 +++++
>  2 files changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 9581906b5ee9..fbc8dfe7da9f 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -330,22 +330,16 @@ _GLOBAL(enter_rtas)
>  	clrldi	r4,r4,2			/* convert to realmode address */
>         	mtlr	r4
>  
> -	li	r0,0
> -	ori	r0,r0,MSR_EE|MSR_SE|MSR_BE|MSR_RI
> -	andc	r0,r6,r0
> -	
> -        li      r9,1
> -        rldicr  r9,r9,MSR_SF_LG,(63-MSR_SF_LG)
> -	ori	r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
> -	andc	r6,r0,r9
> -
>  __enter_rtas:
> -	sync				/* disable interrupts so SRR0/1 */
> -	mtmsrd	r0			/* don't get trashed */
> -
>  	LOAD_REG_ADDR(r4, rtas)
>  	ld	r5,RTASENTRY(r4)	/* get the rtas->entry value */
>  	ld	r4,RTASBASE(r4)		/* get the rtas->base value */
> +
> +	/* RTAS runs in 32bits real mode but we may hit watchdog irq */
> +	LOAD_REG_IMMEDIATE(r6, MSR_ME|MSR_RI)
> +
> +	li      r0,0
> +	mtmsrd  r0,1                    /* disable RI before using SRR0/1 */
>  	
>  	mtspr	SPRN_SRR0,r5
>  	mtspr	SPRN_SRR1,r6
> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index 1f42aabbbab3..d7775b8c8853 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -49,6 +49,11 @@ void enter_rtas(unsigned long);
>  
>  static inline void do_enter_rtas(unsigned long args)
>  {
> +	unsigned long msr;
> +
> +	msr = mfmsr();
> +	BUG_ON(!(msr & MSR_RI));
> +
>  	enter_rtas(args);
>  
>  	srr_regs_clobbered(); /* rtas uses SRRs, invalidate */
> -- 
> 2.35.1
> 
>
Re: [PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS
Posted by Laurent Dufour 4 years, 2 months ago 
On 29/03/2022, 10:31:33, Nicholas Piggin wrote:
> Excerpts from Laurent Dufour's message of March 17, 2022 9:06 pm:
>> RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32bits
>> mode (MSR[SF] unset).
>>
>> The change in MSR is done in enter_rtas() in a relatively complex way,
>> since the MSR value could be hardcoded.
>>
>> Furthermore, a panic has been reported when hitting the watchdog interrupt
>> while running in RTAS, this leads to the following stack trace:
>>
>> [69244.027433][   C24] watchdog: CPU 24 Hard LOCKUP
>> [69244.027442][   C24] watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago)
>> [69244.027451][   C24] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
>> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
>> [69244.027555][   C24]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
>> [69244.027587][   C24] Supported: No, Unreleased kernel
>> [69244.027600][   C24] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
>> [69244.027609][   C24] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
>> [69244.027612][   C24] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
>> [69244.027615][   C24] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
>> [69244.027625][   C24] CFAR: 000000000000011c IRQMASK: 1
>> [69244.027625][   C24] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
>> [69244.027625][   C24] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
>> [69244.027625][   C24] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
>> [69244.027625][   C24] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
>> [69244.027625][   C24] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
>> [69244.027625][   C24] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
>> [69244.027625][   C24] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
>> [69244.027625][   C24] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
>> [69244.027663][   C24] NIP [000000001fb41050] 0x1fb41050
>> [69244.027696][   C24] LR [000000001fb4104c] 0x1fb4104c
>> [69244.027699][   C24] Call Trace:
>> [69244.027701][   C24] Instruction dump:
>> [69244.027723][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>> [69244.027728][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>> [69244.027762][T87504] Oops: Unrecoverable System Reset, sig: 6 [#1]
>> [69244.028044][T87504] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
>> [69244.028089][T87504] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
>> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
>> [69244.028171][T87504]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
>> [69244.028307][T87504] Supported: No, Unreleased kernel
>> [69244.028385][T87504] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
>> [69244.028408][T87504] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
>> [69244.028418][T87504] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
>> [69244.028429][T87504] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
>> [69244.028444][T87504] CFAR: 000000000000011c IRQMASK: 1
>> [69244.028444][T87504] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
>> [69244.028444][T87504] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
>> [69244.028444][T87504] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
>> [69244.028444][T87504] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
>> [69244.028444][T87504] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
>> [69244.028444][T87504] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
>> [69244.028444][T87504] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
>> [69244.028444][T87504] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
>> [69244.028534][T87504] NIP [000000001fb41050] 0x1fb41050
>> [69244.028543][T87504] LR [000000001fb4104c] 0x1fb4104c
>> [69244.028549][T87504] Call Trace:
>> [69244.028554][T87504] Instruction dump:
>> [69244.028561][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>> [69244.028575][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>> [69244.028607][T87504] ---[ end trace 3ddec07f638c34a2 ]---
>>
>> This happens because MSR[RI] is unset when entering RTAS but there is no
>> valid reason to not set it here.
>>
>> Fixing this by reviewing the way MSR is compute before calling RTAS. Now a
>> hardcoded value meaning real mode, 32 bits and Recoverable Interrupt is
>> loaded.
>>
>> In addition a check is added in do_enter_rtas() to detect calls made with
>> MSR[RI] unset, as we are forcing it on later.
> 
> This looks okay to me, I would just adjust the comment about watchdog
> irq. It's more like NMI (SRESET or MCE), watchdog irq could be confusing 
> for the soft-NMI timer.
> 
> Otherwise I think it's okay.
> 
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Thanks Nick,

I agree about comment watchdog irq.
Michael, could you fix that comment below when applying?

> 
>>
>> Cc: stable@vger.kernel.org
>> Suggested-by: Nicholas Piggin <npiggin@gmail.com>
>> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
>> ---
>>  arch/powerpc/kernel/entry_64.S | 18 ++++++------------
>>  arch/powerpc/kernel/rtas.c     |  5 +++++
>>  2 files changed, 11 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
>> index 9581906b5ee9..fbc8dfe7da9f 100644
>> --- a/arch/powerpc/kernel/entry_64.S
>> +++ b/arch/powerpc/kernel/entry_64.S
>> @@ -330,22 +330,16 @@ _GLOBAL(enter_rtas)
>>  	clrldi	r4,r4,2			/* convert to realmode address */
>>         	mtlr	r4
>>  
>> -	li	r0,0
>> -	ori	r0,r0,MSR_EE|MSR_SE|MSR_BE|MSR_RI
>> -	andc	r0,r6,r0
>> -	
>> -        li      r9,1
>> -        rldicr  r9,r9,MSR_SF_LG,(63-MSR_SF_LG)
>> -	ori	r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
>> -	andc	r6,r0,r9
>> -
>>  __enter_rtas:
>> -	sync				/* disable interrupts so SRR0/1 */
>> -	mtmsrd	r0			/* don't get trashed */
>> -
>>  	LOAD_REG_ADDR(r4, rtas)
>>  	ld	r5,RTASENTRY(r4)	/* get the rtas->entry value */
>>  	ld	r4,RTASBASE(r4)		/* get the rtas->base value */
>> +
>> +	/* RTAS runs in 32bits real mode but we may hit watchdog irq */

Here I guess something like:
	/* RTAS runs in 32Bits real mode, but we may hit NMI irq */

Thanks,
Laurent.

>> +	LOAD_REG_IMMEDIATE(r6, MSR_ME|MSR_RI)
>> +
>> +	li      r0,0
>> +	mtmsrd  r0,1                    /* disable RI before using SRR0/1 */
>>  	
>>  	mtspr	SPRN_SRR0,r5
>>  	mtspr	SPRN_SRR1,r6
>> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
>> index 1f42aabbbab3..d7775b8c8853 100644
>> --- a/arch/powerpc/kernel/rtas.c
>> +++ b/arch/powerpc/kernel/rtas.c
>> @@ -49,6 +49,11 @@ void enter_rtas(unsigned long);
>>  
>>  static inline void do_enter_rtas(unsigned long args)
>>  {
>> +	unsigned long msr;
>> +
>> +	msr = mfmsr();
>> +	BUG_ON(!(msr & MSR_RI));
>> +
>>  	enter_rtas(args);
>>  
>>  	srr_regs_clobbered(); /* rtas uses SRRs, invalidate */
>> -- 
>> 2.35.1
>>
>>
Re: [PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS
Posted by Michael Ellerman 4 years, 2 months ago 
Laurent Dufour <ldufour@linux.ibm.com> writes:
> On 29/03/2022, 10:31:33, Nicholas Piggin wrote:
>> Excerpts from Laurent Dufour's message of March 17, 2022 9:06 pm:
>>> RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32bits
>>> mode (MSR[SF] unset).
>>>
>>> The change in MSR is done in enter_rtas() in a relatively complex way,
>>> since the MSR value could be hardcoded.
>>>
>>> Furthermore, a panic has been reported when hitting the watchdog interrupt
>>> while running in RTAS, this leads to the following stack trace:
>>>
>>> [69244.027433][   C24] watchdog: CPU 24 Hard LOCKUP
>>> [69244.027442][   C24] watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago)
>>> [69244.027451][   C24] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
>>> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
>>> [69244.027555][   C24]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
>>> [69244.027587][   C24] Supported: No, Unreleased kernel
>>> [69244.027600][   C24] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
>>> [69244.027609][   C24] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
>>> [69244.027612][   C24] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
>>> [69244.027615][   C24] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
>>> [69244.027625][   C24] CFAR: 000000000000011c IRQMASK: 1
>>> [69244.027625][   C24] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
>>> [69244.027625][   C24] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
>>> [69244.027625][   C24] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
>>> [69244.027625][   C24] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
>>> [69244.027625][   C24] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
>>> [69244.027625][   C24] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
>>> [69244.027625][   C24] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
>>> [69244.027625][   C24] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
>>> [69244.027663][   C24] NIP [000000001fb41050] 0x1fb41050
>>> [69244.027696][   C24] LR [000000001fb4104c] 0x1fb4104c
>>> [69244.027699][   C24] Call Trace:
>>> [69244.027701][   C24] Instruction dump:
>>> [69244.027723][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>> [69244.027728][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>> [69244.027762][T87504] Oops: Unrecoverable System Reset, sig: 6 [#1]
>>> [69244.028044][T87504] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
>>> [69244.028089][T87504] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
>>> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
>>> [69244.028171][T87504]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
>>> [69244.028307][T87504] Supported: No, Unreleased kernel
>>> [69244.028385][T87504] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
>>> [69244.028408][T87504] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
>>> [69244.028418][T87504] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
>>> [69244.028429][T87504] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
>>> [69244.028444][T87504] CFAR: 000000000000011c IRQMASK: 1
>>> [69244.028444][T87504] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
>>> [69244.028444][T87504] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
>>> [69244.028444][T87504] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
>>> [69244.028444][T87504] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
>>> [69244.028444][T87504] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
>>> [69244.028444][T87504] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
>>> [69244.028444][T87504] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
>>> [69244.028444][T87504] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
>>> [69244.028534][T87504] NIP [000000001fb41050] 0x1fb41050
>>> [69244.028543][T87504] LR [000000001fb4104c] 0x1fb4104c
>>> [69244.028549][T87504] Call Trace:
>>> [69244.028554][T87504] Instruction dump:
>>> [69244.028561][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>> [69244.028575][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>> [69244.028607][T87504] ---[ end trace 3ddec07f638c34a2 ]---
>>>
>>> This happens because MSR[RI] is unset when entering RTAS but there is no
>>> valid reason to not set it here.
>>>
>>> Fixing this by reviewing the way MSR is compute before calling RTAS. Now a
>>> hardcoded value meaning real mode, 32 bits and Recoverable Interrupt is
>>> loaded.
>>>
>>> In addition a check is added in do_enter_rtas() to detect calls made with
>>> MSR[RI] unset, as we are forcing it on later.
>> 
>> This looks okay to me, I would just adjust the comment about watchdog
>> irq. It's more like NMI (SRESET or MCE), watchdog irq could be confusing 
>> for the soft-NMI timer.
>> 
>> Otherwise I think it's okay.
>> 
>> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>
> Thanks Nick,
>
> I agree about comment watchdog irq.
> Michael, could you fix that comment below when applying?

I can.

But the changelog also needs to mention that what we're doing is legal
per PAPR, and reference the relevant sections.

I think that's section "7.2.1 Machine State", in particular:

  R1–7.2.1–9. If called with MSR[RI]equal to 1, then RTAS must protect
  its own critical regions from recursion by setting the MSR[RI] bit to
  0 when in the critical regions.

That language appears to go back to PAPR+ Version 1.0, so that should
cover all PAPR systems.

We also had RTAS on pre-PAPR systems, but I don't think we support any
of those anymore (on 64-bit).

Would also be good to know what machines you've tested this on.

cheers
Re: [PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS
Posted by Laurent Dufour 4 years, 2 months ago 
On 29/03/2022, 13:14:10, Michael Ellerman wrote:
> Laurent Dufour <ldufour@linux.ibm.com> writes:
>> On 29/03/2022, 10:31:33, Nicholas Piggin wrote:
>>> Excerpts from Laurent Dufour's message of March 17, 2022 9:06 pm:
>>>> RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32bits
>>>> mode (MSR[SF] unset).
>>>>
>>>> The change in MSR is done in enter_rtas() in a relatively complex way,
>>>> since the MSR value could be hardcoded.
>>>>
>>>> Furthermore, a panic has been reported when hitting the watchdog interrupt
>>>> while running in RTAS, this leads to the following stack trace:
>>>>
>>>> [69244.027433][   C24] watchdog: CPU 24 Hard LOCKUP
>>>> [69244.027442][   C24] watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago)
>>>> [69244.027451][   C24] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
>>>> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
>>>> [69244.027555][   C24]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
>>>> [69244.027587][   C24] Supported: No, Unreleased kernel
>>>> [69244.027600][   C24] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
>>>> [69244.027609][   C24] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
>>>> [69244.027612][   C24] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
>>>> [69244.027615][   C24] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
>>>> [69244.027625][   C24] CFAR: 000000000000011c IRQMASK: 1
>>>> [69244.027625][   C24] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
>>>> [69244.027625][   C24] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
>>>> [69244.027625][   C24] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
>>>> [69244.027625][   C24] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
>>>> [69244.027625][   C24] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
>>>> [69244.027625][   C24] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
>>>> [69244.027625][   C24] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
>>>> [69244.027625][   C24] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
>>>> [69244.027663][   C24] NIP [000000001fb41050] 0x1fb41050
>>>> [69244.027696][   C24] LR [000000001fb4104c] 0x1fb4104c
>>>> [69244.027699][   C24] Call Trace:
>>>> [69244.027701][   C24] Instruction dump:
>>>> [69244.027723][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>>> [69244.027728][   C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>>> [69244.027762][T87504] Oops: Unrecoverable System Reset, sig: 6 [#1]
>>>> [69244.028044][T87504] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
>>>> [69244.028089][T87504] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
>>>> nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
>>>> [69244.028171][T87504]  ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
>>>> [69244.028307][T87504] Supported: No, Unreleased kernel
>>>> [69244.028385][T87504] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G            E  X    5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
>>>> [69244.028408][T87504] NIP:  000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
>>>> [69244.028418][T87504] REGS: c00000000fc33d60 TRAP: 0100   Tainted: G            E  X     (5.14.21-150400.71.1.bz196362_2-default)
>>>> [69244.028429][T87504] MSR:  8000000002981000 <SF,VEC,VSX,ME>  CR: 48800002  XER: 20040020
>>>> [69244.028444][T87504] CFAR: 000000000000011c IRQMASK: 1
>>>> [69244.028444][T87504] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
>>>> [69244.028444][T87504] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
>>>> [69244.028444][T87504] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
>>>> [69244.028444][T87504] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
>>>> [69244.028444][T87504] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
>>>> [69244.028444][T87504] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
>>>> [69244.028444][T87504] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
>>>> [69244.028444][T87504] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
>>>> [69244.028534][T87504] NIP [000000001fb41050] 0x1fb41050
>>>> [69244.028543][T87504] LR [000000001fb4104c] 0x1fb4104c
>>>> [69244.028549][T87504] Call Trace:
>>>> [69244.028554][T87504] Instruction dump:
>>>> [69244.028561][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>>> [69244.028575][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
>>>> [69244.028607][T87504] ---[ end trace 3ddec07f638c34a2 ]---
>>>>
>>>> This happens because MSR[RI] is unset when entering RTAS but there is no
>>>> valid reason to not set it here.
>>>>
>>>> Fixing this by reviewing the way MSR is compute before calling RTAS. Now a
>>>> hardcoded value meaning real mode, 32 bits and Recoverable Interrupt is
>>>> loaded.
>>>>
>>>> In addition a check is added in do_enter_rtas() to detect calls made with
>>>> MSR[RI] unset, as we are forcing it on later.
>>>
>>> This looks okay to me, I would just adjust the comment about watchdog
>>> irq. It's more like NMI (SRESET or MCE), watchdog irq could be confusing 
>>> for the soft-NMI timer.
>>>
>>> Otherwise I think it's okay.
>>>
>>> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>>
>> Thanks Nick,
>>
>> I agree about comment watchdog irq.
>> Michael, could you fix that comment below when applying?
> 
> I can.

Thanks, Michael

> 
> But the changelog also needs to mention that what we're doing is legal
> per PAPR, and reference the relevant sections.
> 
> I think that's section "7.2.1 Machine State", in particular:
> 
>   R1–7.2.1–9. If called with MSR[RI]equal to 1, then RTAS must protect
>   its own critical regions from recursion by setting the MSR[RI] bit to
>   0 when in the critical regions.
> 
> That language appears to go back to PAPR+ Version 1.0, so that should
> cover all PAPR systems.

I agree, referencing this section would be good, I don't have the complete
PAPR+ series, the oldest one I've access to is 2.7, and it is already
mentioning this.

> 
> We also had RTAS on pre-PAPR systems, but I don't think we support any
> of those anymore (on 64-bit).

Unfortunately, I have no knowledge on these systems, neither I'm aware of
such a system I have access to. Do you have any pointer?

> Would also be good to know what machines you've tested this on.

Tests have been done on various systems:
Power KVM Guest
  P8 S822L (host Ubuntu kernel 5.11.0-49-generic)
PowerVM LPAR
  P8 9119-MME (FW860.A1)
  p9 9008-22L (FW950.00)
  P10 9080-HEX (FW1010.00)

Should I send a new version with the commit description updated, and the
comment fixed in the code?

Thanks,
Laurent.

Patchew 2.1-devel-ea86937

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