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Peter Anvin" Subject: [PATCH v2 1/2] x86/xen: remove xen_have_vcpu_info_placement flag Date: Wed, 22 Sep 2021 12:31:01 +0200 Message-Id: <20210922103102.3589-2-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210922103102.3589-1-jgross@suse.com> References: <20210922103102.3589-1-jgross@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1632306690985100001 Content-Type: text/plain; charset="utf-8" The flag xen_have_vcpu_info_placement was needed to support Xen hypervisors older than version 3.4. Today the Linux kernel requires at least Xen 4.0 to be able to run, so xen_have_vcpu_info_placement can be dropped. This allows to let some functions return void now, as they can never fail. Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky --- arch/x86/xen/enlighten.c | 97 +++++++++--------------------------- arch/x86/xen/enlighten_hvm.c | 6 +-- arch/x86/xen/enlighten_pv.c | 28 ++--------- arch/x86/xen/smp.c | 24 --------- arch/x86/xen/xen-ops.h | 4 +- 5 files changed, 33 insertions(+), 126 deletions(-) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index c79bd0af2e8c..8a7bd3f4591e 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -81,21 +81,6 @@ EXPORT_SYMBOL(xen_start_flags); */ struct shared_info *HYPERVISOR_shared_info =3D &xen_dummy_shared_info; =20 -/* - * Flag to determine whether vcpu info placement is available on all - * VCPUs. We assume it is to start with, and then set it to zero on - * the first failure. This is because it can succeed on some VCPUs - * and not others, since it can involve hypervisor memory allocation, - * or because the guest failed to guarantee all the appropriate - * constraints on all VCPUs (ie buffer can't cross a page boundary). - * - * Note that any particular CPU may be using a placed vcpu structure, - * but we can only optimise if the all are. - * - * 0: not available, 1: available - */ -int xen_have_vcpu_info_placement =3D 1; - static int xen_cpu_up_online(unsigned int cpu) { xen_init_lock_cpu(cpu); @@ -121,10 +106,8 @@ int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned = int), return rc >=3D 0 ? 0 : rc; } =20 -static int xen_vcpu_setup_restore(int cpu) +static void xen_vcpu_setup_restore(int cpu) { - int rc =3D 0; - /* Any per_cpu(xen_vcpu) is stale, so reset it */ xen_vcpu_info_reset(cpu); =20 @@ -133,11 +116,8 @@ static int xen_vcpu_setup_restore(int cpu) * be handled by hotplug. */ if (xen_pv_domain() || - (xen_hvm_domain() && cpu_online(cpu))) { - rc =3D xen_vcpu_setup(cpu); - } - - return rc; + (xen_hvm_domain() && cpu_online(cpu))) + xen_vcpu_setup(cpu); } =20 /* @@ -147,7 +127,7 @@ static int xen_vcpu_setup_restore(int cpu) */ void xen_vcpu_restore(void) { - int cpu, rc; + int cpu; =20 for_each_possible_cpu(cpu) { bool other_cpu =3D (cpu !=3D smp_processor_id()); @@ -167,20 +147,9 @@ void xen_vcpu_restore(void) if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock)) xen_setup_runstate_info(cpu); =20 - rc =3D xen_vcpu_setup_restore(cpu); - if (rc) - pr_emerg_once("vcpu restore failed for cpu=3D%d err=3D%d. " - "System will hang.\n", cpu, rc); - /* - * In case xen_vcpu_setup_restore() fails, do not bring up the - * VCPU. This helps us avoid the resulting OOPS when the VCPU - * accesses pvclock_vcpu_time via xen_vcpu (which is NULL.) - * Note that this does not improve the situation much -- now the - * VM hangs instead of OOPSing -- with the VCPUs that did not - * fail, spinning in stop_machine(), waiting for the failed - * VCPUs to come up. - */ - if (other_cpu && is_up && (rc =3D=3D 0) && + xen_vcpu_setup_restore(cpu); + + if (other_cpu && is_up && HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL)) BUG(); } @@ -197,7 +166,7 @@ void xen_vcpu_info_reset(int cpu) } } =20 -int xen_vcpu_setup(int cpu) +void xen_vcpu_setup(int cpu) { struct vcpu_register_vcpu_info info; int err; @@ -218,44 +187,26 @@ int xen_vcpu_setup(int cpu) */ if (xen_hvm_domain()) { if (per_cpu(xen_vcpu, cpu) =3D=3D &per_cpu(xen_vcpu_info, cpu)) - return 0; + return; } =20 - if (xen_have_vcpu_info_placement) { - vcpup =3D &per_cpu(xen_vcpu_info, cpu); - info.mfn =3D arbitrary_virt_to_mfn(vcpup); - info.offset =3D offset_in_page(vcpup); + vcpup =3D &per_cpu(xen_vcpu_info, cpu); + info.mfn =3D arbitrary_virt_to_mfn(vcpup); + info.offset =3D offset_in_page(vcpup); =20 - /* - * Check to see if the hypervisor will put the vcpu_info - * structure where we want it, which allows direct access via - * a percpu-variable. - * N.B. This hypercall can _only_ be called once per CPU. - * Subsequent calls will error out with -EINVAL. This is due to - * the fact that hypervisor has no unregister variant and this - * hypercall does not allow to over-write info.mfn and - * info.offset. - */ - err =3D HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, - xen_vcpu_nr(cpu), &info); - - if (err) { - pr_warn_once("register_vcpu_info failed: cpu=3D%d err=3D%d\n", - cpu, err); - xen_have_vcpu_info_placement =3D 0; - } else { - /* - * This cpu is using the registered vcpu info, even if - * later ones fail to. - */ - per_cpu(xen_vcpu, cpu) =3D vcpup; - } - } - - if (!xen_have_vcpu_info_placement) - xen_vcpu_info_reset(cpu); + /* + * N.B. This hypercall can _only_ be called once per CPU. + * Subsequent calls will error out with -EINVAL. This is due to + * the fact that hypervisor has no unregister variant and this + * hypercall does not allow to over-write info.mfn and + * info.offset. + */ + err =3D HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu), + &info); + if (err) + panic("register_vcpu_info failed: cpu=3D%d err=3D%d\n", cpu, err); =20 - return ((per_cpu(xen_vcpu, cpu) =3D=3D NULL) ? -ENODEV : 0); + per_cpu(xen_vcpu, cpu) =3D vcpup; } =20 void xen_reboot(int reason) diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c index e68ea5f4ad1c..42300941ec29 100644 --- a/arch/x86/xen/enlighten_hvm.c +++ b/arch/x86/xen/enlighten_hvm.c @@ -163,9 +163,9 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu) per_cpu(xen_vcpu_id, cpu) =3D cpu_acpi_id(cpu); else per_cpu(xen_vcpu_id, cpu) =3D cpu; - rc =3D xen_vcpu_setup(cpu); - if (rc || !xen_have_vector_callback) - return rc; + xen_vcpu_setup(cpu); + if (!xen_have_vector_callback) + return 0; =20 if (xen_feature(XENFEAT_hvm_safe_pvclock)) xen_setup_timer(cpu); diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 349f780a1567..6719963901e5 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1018,31 +1018,13 @@ void __init xen_setup_vcpu_info_placement(void) for_each_possible_cpu(cpu) { /* Set up direct vCPU id mapping for PV guests. */ per_cpu(xen_vcpu_id, cpu) =3D cpu; - - /* - * xen_vcpu_setup(cpu) can fail -- in which case it - * falls back to the shared_info version for cpus - * where xen_vcpu_nr(cpu) < MAX_VIRT_CPUS. - * - * xen_cpu_up_prepare_pv() handles the rest by failing - * them in hotplug. - */ - (void) xen_vcpu_setup(cpu); + xen_vcpu_setup(cpu); } =20 - /* - * xen_vcpu_setup managed to place the vcpu_info within the - * percpu area for all cpus, so make use of it. - */ - if (xen_have_vcpu_info_placement) { - pv_ops.irq.save_fl =3D __PV_IS_CALLEE_SAVE(xen_save_fl_direct); - pv_ops.irq.irq_disable =3D - __PV_IS_CALLEE_SAVE(xen_irq_disable_direct); - pv_ops.irq.irq_enable =3D - __PV_IS_CALLEE_SAVE(xen_irq_enable_direct); - pv_ops.mmu.read_cr2 =3D - __PV_IS_CALLEE_SAVE(xen_read_cr2_direct); - } + pv_ops.irq.save_fl =3D __PV_IS_CALLEE_SAVE(xen_save_fl_direct); + pv_ops.irq.irq_disable =3D __PV_IS_CALLEE_SAVE(xen_irq_disable_direct); + pv_ops.irq.irq_enable =3D __PV_IS_CALLEE_SAVE(xen_irq_enable_direct); + pv_ops.mmu.read_cr2 =3D __PV_IS_CALLEE_SAVE(xen_read_cr2_direct); } =20 static const struct pv_info xen_info __initconst =3D { diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index c1b2f764b29a..bafa61b1482f 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -121,34 +121,10 @@ int xen_smp_intr_init(unsigned int cpu) =20 void __init xen_smp_cpus_done(unsigned int max_cpus) { - int cpu, rc, count =3D 0; - if (xen_hvm_domain()) native_smp_cpus_done(max_cpus); else calculate_max_logical_packages(); - - if (xen_have_vcpu_info_placement) - return; - - for_each_online_cpu(cpu) { - if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS) - continue; - - rc =3D remove_cpu(cpu); - - if (rc =3D=3D 0) { - /* - * Reset vcpu_info so this cpu cannot be onlined again. - */ - xen_vcpu_info_reset(cpu); - count++; - } else { - pr_warn("%s: failed to bring CPU %d down, error %d\n", - __func__, cpu, rc); - } - } - WARN(count, "%s: brought %d CPUs offline\n", __func__, count); } =20 void xen_smp_send_reschedule(int cpu) diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index 8d7ec49a35fb..c2da84484b8d 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -75,9 +75,7 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id); =20 bool xen_vcpu_stolen(int vcpu); =20 -extern int xen_have_vcpu_info_placement; - -int xen_vcpu_setup(int cpu); +void xen_vcpu_setup(int cpu); void xen_vcpu_info_reset(int cpu); void xen_setup_vcpu_info_placement(void); =20 --=20 2.26.2