File hvm/vm_event.c and x86/vm_event.c are the extend to vm_event handling
routines, and its compilation shall be guarded by CONFIG_VM_EVENT too.
Although CONFIG_VM_EVENT is right now forcibly enabled on x86 via
MEM_ACCESS_ALWAYS_ON, we could disable it through disabling
CONFIG_MGMT_HYPERCALLS later. So we remove MEM_ACCESS_ALWAYS_ON and
make VM_EVENT=y on default only on x86 to retain the same.
The following functions are developed on the basis of vm event framework, or
only invoked by vm_event.c, so they all shall be wrapped with CONFIG_VM_EVENT
(otherwise they will become unreachable and
violate Misra rule 2.1 when VM_EVENT=n):
- hvm_toggle_singlestep
- hvm_fast_singlestep
- hvm_emulate_one_vm_event
- hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
And Function vm_event_check_ring() needs stub to pass compilation when
VM_EVENT=n.
Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
---
v1 -> v2:
- split out XSM changes
- remove unnecessary stubs
- move "struct p2m_domain" declaration ahead of the #ifdef
---
v2 -> v3:
- move .enable_msr_interception and .set_descriptor_access_exiting together
- with the introduction of "vm_event_is_enabled()", all hvm_monitor_xxx()
stubs are no longer needed
- change to use in-place stubs in do_altp2m_op()
- no need to add stub for monitor_traps(), __vm_event_claim_slot(),
vm_event_put_request() and vm_event_vcpu_pause()
- remove MEM_ACCESS_ALWAYS_ON
- return default p2m_access_rwx for xenmem_access_to_p2m_access() when
VM_EVENT=n
- add wrapping for hvm_emulate_one_vm_event/
hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
---
xen/arch/x86/Makefile | 2 +-
xen/arch/x86/hvm/Kconfig | 1 -
xen/arch/x86/hvm/Makefile | 2 +-
xen/arch/x86/hvm/emulate.c | 58 ++++++++++++++++++++------------------
xen/arch/x86/hvm/hvm.c | 2 ++
xen/common/Kconfig | 7 ++---
xen/include/xen/vm_event.h | 7 +++++
7 files changed, 44 insertions(+), 35 deletions(-)
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 407571c510..f71ca9f18b 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -75,7 +75,7 @@ obj-y += usercopy.o
obj-y += x86_emulate.o
obj-$(CONFIG_TBOOT) += tboot.o
obj-y += hpet.o
-obj-y += vm_event.o
+obj-$(CONFIG_VM_EVENT) += vm_event.o
obj-y += xstate.o
ifneq ($(CONFIG_PV_SHIM_EXCLUSIVE),y)
diff --git a/xen/arch/x86/hvm/Kconfig b/xen/arch/x86/hvm/Kconfig
index f10a2b3744..ea957363a9 100644
--- a/xen/arch/x86/hvm/Kconfig
+++ b/xen/arch/x86/hvm/Kconfig
@@ -4,7 +4,6 @@ menuconfig HVM
default !PV_SHIM
select COMPAT
select IOREQ_SERVER
- select MEM_ACCESS_ALWAYS_ON
help
Interfaces to support HVM domains. HVM domains require hardware
virtualisation extensions (e.g. Intel VT-x, AMD SVM), but can boot
diff --git a/xen/arch/x86/hvm/Makefile b/xen/arch/x86/hvm/Makefile
index 50e0b6e63b..952db00dd7 100644
--- a/xen/arch/x86/hvm/Makefile
+++ b/xen/arch/x86/hvm/Makefile
@@ -26,7 +26,7 @@ obj-y += save.o
obj-y += stdvga.o
obj-y += vioapic.o
obj-y += vlapic.o
-obj-y += vm_event.o
+obj-$(CONFIG_VM_EVENT) += vm_event.o
obj-y += vmsi.o
obj-y += vpic.o
obj-y += vpt.o
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index fe75b0516d..d56ef02baf 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1615,6 +1615,7 @@ static int cf_check hvmemul_blk(
return rc;
}
+#ifdef CONFIG_VM_EVENT
static int cf_check hvmemul_write_discard(
enum x86_segment seg,
unsigned long offset,
@@ -1717,6 +1718,7 @@ static int cf_check hvmemul_cache_op_discard(
{
return X86EMUL_OKAY;
}
+#endif /* CONFIG_VM_EVENT */
static int cf_check hvmemul_cmpxchg(
enum x86_segment seg,
@@ -2750,33 +2752,6 @@ static const struct x86_emulate_ops hvm_emulate_ops = {
.vmfunc = hvmemul_vmfunc,
};
-static const struct x86_emulate_ops hvm_emulate_ops_no_write = {
- .read = hvmemul_read,
- .insn_fetch = hvmemul_insn_fetch,
- .write = hvmemul_write_discard,
- .cmpxchg = hvmemul_cmpxchg_discard,
- .rep_ins = hvmemul_rep_ins_discard,
- .rep_outs = hvmemul_rep_outs_discard,
- .rep_movs = hvmemul_rep_movs_discard,
- .rep_stos = hvmemul_rep_stos_discard,
- .read_segment = hvmemul_read_segment,
- .write_segment = hvmemul_write_segment,
- .read_io = hvmemul_read_io_discard,
- .write_io = hvmemul_write_io_discard,
- .read_cr = hvmemul_read_cr,
- .write_cr = hvmemul_write_cr,
- .read_xcr = hvmemul_read_xcr,
- .write_xcr = hvmemul_write_xcr,
- .read_msr = hvmemul_read_msr,
- .write_msr = hvmemul_write_msr_discard,
- .cache_op = hvmemul_cache_op_discard,
- .tlb_op = hvmemul_tlb_op,
- .cpuid = x86emul_cpuid,
- .get_fpu = hvmemul_get_fpu,
- .put_fpu = hvmemul_put_fpu,
- .vmfunc = hvmemul_vmfunc,
-};
-
/*
* Note that passing VIO_no_completion into this function serves as kind
* of (but not fully) an "auto select completion" indicator. When there's
@@ -2887,6 +2862,34 @@ int hvm_emulate_one(
return _hvm_emulate_one(hvmemul_ctxt, &hvm_emulate_ops, completion);
}
+#ifdef CONFIG_VM_EVENT
+static const struct x86_emulate_ops hvm_emulate_ops_no_write = {
+ .read = hvmemul_read,
+ .insn_fetch = hvmemul_insn_fetch,
+ .write = hvmemul_write_discard,
+ .cmpxchg = hvmemul_cmpxchg_discard,
+ .rep_ins = hvmemul_rep_ins_discard,
+ .rep_outs = hvmemul_rep_outs_discard,
+ .rep_movs = hvmemul_rep_movs_discard,
+ .rep_stos = hvmemul_rep_stos_discard,
+ .read_segment = hvmemul_read_segment,
+ .write_segment = hvmemul_write_segment,
+ .read_io = hvmemul_read_io_discard,
+ .write_io = hvmemul_write_io_discard,
+ .read_cr = hvmemul_read_cr,
+ .write_cr = hvmemul_write_cr,
+ .read_xcr = hvmemul_read_xcr,
+ .write_xcr = hvmemul_write_xcr,
+ .read_msr = hvmemul_read_msr,
+ .write_msr = hvmemul_write_msr_discard,
+ .cache_op = hvmemul_cache_op_discard,
+ .tlb_op = hvmemul_tlb_op,
+ .cpuid = x86emul_cpuid,
+ .get_fpu = hvmemul_get_fpu,
+ .put_fpu = hvmemul_put_fpu,
+ .vmfunc = hvmemul_vmfunc,
+};
+
void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
unsigned int errcode)
{
@@ -2949,6 +2952,7 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
hvm_emulate_writeback(&ctx);
}
+#endif /* CONFIG_VM_EVENT */
void hvm_emulate_init_once(
struct hvm_emulate_ctxt *hvmemul_ctxt,
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index c3417b0593..196de2db67 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5297,6 +5297,7 @@ int hvm_debug_op(struct vcpu *v, int32_t op)
return rc;
}
+#ifdef CONFIG_VM_EVENT
void hvm_toggle_singlestep(struct vcpu *v)
{
ASSERT(atomic_read(&v->pause_count));
@@ -5323,6 +5324,7 @@ void hvm_fast_singlestep(struct vcpu *v, uint16_t p2midx)
v->arch.hvm.fast_single_step.p2midx = p2midx;
}
#endif
+#endif /* CONFIG_VM_EVENT */
/*
* Segment caches in VMCB/VMCS are inconsistent about which bits are checked,
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 53f681bbb2..0070fe42a6 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -170,13 +170,10 @@ config HAS_VMAP
config LIBFDT
bool
-config MEM_ACCESS_ALWAYS_ON
- bool
-
config VM_EVENT
- def_bool MEM_ACCESS_ALWAYS_ON
- prompt "Memory Access and VM events" if !MEM_ACCESS_ALWAYS_ON
+ bool "Memory Access and VM events"
depends on HVM
+ default X86
help
Framework to configure memory access types for guests and receive
diff --git a/xen/include/xen/vm_event.h b/xen/include/xen/vm_event.h
index 27d0c74216..1b76ce632e 100644
--- a/xen/include/xen/vm_event.h
+++ b/xen/include/xen/vm_event.h
@@ -51,7 +51,14 @@ struct vm_event_domain
};
/* Returns whether a ring has been set up */
+#ifdef CONFIG_VM_EVENT
bool vm_event_check_ring(struct vm_event_domain *ved);
+#else
+static inline bool vm_event_check_ring(struct vm_event_domain *ved)
+{
+ return false;
+}
+#endif /* CONFIG_VM_EVENT */
/* Returns 0 on success, -ENOSYS if there is no ring, -EBUSY if there is no
* available space and the caller is a foreign domain. If the guest itself
--
2.34.1On 13.11.2025 04:16, Penny Zheng wrote:
> File hvm/vm_event.c and x86/vm_event.c are the extend to vm_event handling
> routines, and its compilation shall be guarded by CONFIG_VM_EVENT too.
>
> Although CONFIG_VM_EVENT is right now forcibly enabled on x86 via
> MEM_ACCESS_ALWAYS_ON, we could disable it through disabling
> CONFIG_MGMT_HYPERCALLS later. So we remove MEM_ACCESS_ALWAYS_ON and
> make VM_EVENT=y on default only on x86 to retain the same.
>
> The following functions are developed on the basis of vm event framework, or
> only invoked by vm_event.c, so they all shall be wrapped with CONFIG_VM_EVENT
> (otherwise they will become unreachable and
> violate Misra rule 2.1 when VM_EVENT=n):
> - hvm_toggle_singlestep
> - hvm_fast_singlestep
> - hvm_emulate_one_vm_event
> - hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
> And Function vm_event_check_ring() needs stub to pass compilation when
> VM_EVENT=n.
>
> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
> ---
> v1 -> v2:
> - split out XSM changes
Isn't that split out patch also needed as a prereq to the one here? The one
here on its own:
Acked-by: Jan Beulich <jbeulich@suse.com>
But the possibly missing dependency question needs addressing before this may
go in.
> - remove unnecessary stubs
> - move "struct p2m_domain" declaration ahead of the #ifdef
> ---
> v2 -> v3:
> - move .enable_msr_interception and .set_descriptor_access_exiting together
> - with the introduction of "vm_event_is_enabled()", all hvm_monitor_xxx()
> stubs are no longer needed
> - change to use in-place stubs in do_altp2m_op()
> - no need to add stub for monitor_traps(), __vm_event_claim_slot(),
> vm_event_put_request() and vm_event_vcpu_pause()
> - remove MEM_ACCESS_ALWAYS_ON
> - return default p2m_access_rwx for xenmem_access_to_p2m_access() when
> VM_EVENT=n
> - add wrapping for hvm_emulate_one_vm_event/
> hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
> ---
No changes at all in this version? The v3 patch was much larger, after all.
Jan
On 2025-11-13 05:16, Jan Beulich wrote:
> On 13.11.2025 04:16, Penny Zheng wrote:
>> File hvm/vm_event.c and x86/vm_event.c are the extend to vm_event handling
>> routines, and its compilation shall be guarded by CONFIG_VM_EVENT too.
>>
>> Although CONFIG_VM_EVENT is right now forcibly enabled on x86 via
>> MEM_ACCESS_ALWAYS_ON, we could disable it through disabling
>> CONFIG_MGMT_HYPERCALLS later. So we remove MEM_ACCESS_ALWAYS_ON and
>> make VM_EVENT=y on default only on x86 to retain the same.
>>
>> The following functions are developed on the basis of vm event framework, or
>> only invoked by vm_event.c, so they all shall be wrapped with CONFIG_VM_EVENT
>> (otherwise they will become unreachable and
>> violate Misra rule 2.1 when VM_EVENT=n):
>> - hvm_toggle_singlestep
>> - hvm_fast_singlestep
>> - hvm_emulate_one_vm_event
>> - hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
>> And Function vm_event_check_ring() needs stub to pass compilation when
>> VM_EVENT=n.
>>
>> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
>> ---
>> v1 -> v2:
>> - split out XSM changes
>
> Isn't that split out patch also needed as a prereq to the one here? The one
> here on its own:
> Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
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