diff mbox series

[v3,14/18] KVM: SVM: Check that the current CPU supports SVM in kvm_is_svm_supported()

Message ID 20230512235026.808058-15-seanjc@google.com
State New
Headers
Series x86/reboot: KVM: Clean up "emergency" virt code |

Commit Message

Sean Christopherson May 12, 2023, 11:50 p.m. UTC 
  Check "this" CPU instead of the boot CPU when querying SVM support so that
the per-CPU checks done during hardware enabling actually function as
intended, i.e. will detect issues where SVM isn't support on all CPUs.

Disable migration for the use from svm_init() mostly so that the standard
accessors for the per-CPU data can be used without getting yelled at by
CONFIG_DEBUG_PREEMPT=y sanity checks.  Preventing the "disabled by BIOS"
error message from reporting the wrong CPU is largely a bonus, as ensuring
a stable CPU during module load is a non-goal for KVM.

Link: https://lore.kernel.org/all/ZAdxNgv0M6P63odE@google.com
Cc: Kai Huang <kai.huang@intel.com>
Cc: Chao Gao <chao.gao@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

Comments

Kai Huang May 22, 2023, 11:18 p.m. UTC | #1 
On Fri, 2023-05-12 at 16:50 -0700, Sean Christopherson wrote:
> Check "this" CPU instead of the boot CPU when querying SVM support so that
> the per-CPU checks done during hardware enabling actually function as
> intended, i.e. will detect issues where SVM isn't support on all CPUs.
> 
> Disable migration for the use from svm_init() mostly so that the standard
> accessors for the per-CPU data can be used without getting yelled at by
> CONFIG_DEBUG_PREEMPT=y sanity checks.  Preventing the "disabled by BIOS"
> error message from reporting the wrong CPU is largely a bonus, as ensuring
> a stable CPU during module load is a non-goal for KVM.

"non-goal for KVM (at least for now)" ? :)

> 
> Link: https://lore.kernel.org/all/ZAdxNgv0M6P63odE@google.com
> Cc: Kai Huang <kai.huang@intel.com>
> Cc: Chao Gao <chao.gao@intel.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Kai Huang <kai.huang@intel.com>

> ---
>  arch/x86/kvm/svm/svm.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index b347173b4e29..cf5f3880751b 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -523,18 +523,20 @@ static void svm_init_osvw(struct kvm_vcpu *vcpu)
>  		vcpu->arch.osvw.status |= 1;
>  }
>  
> -static bool kvm_is_svm_supported(void)
> +static bool __kvm_is_svm_supported(void)
>  {
> -	int cpu = raw_smp_processor_id();
> +	int cpu = smp_processor_id();
> +	struct cpuinfo_x86 *c = &cpu_data(cpu);
> +
>  	u64 vm_cr;
>  
> -	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
> -	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) {
> +	if (c->x86_vendor != X86_VENDOR_AMD &&
> +	    c->x86_vendor != X86_VENDOR_HYGON) {
>  		pr_err("CPU %d isn't AMD or Hygon\n", cpu);
>  		return false;
>  	}
>  
> -	if (!boot_cpu_has(X86_FEATURE_SVM)) {
> +	if (!cpu_has(c, X86_FEATURE_SVM)) {
>  		pr_err("SVM not supported by CPU %d\n", cpu);
>  		return false;
>  	}
> @@ -553,9 +555,20 @@ static bool kvm_is_svm_supported(void)
>  	return true;
>  }
>  
> +static bool kvm_is_svm_supported(void)
> +{
> +	bool supported;
> +
> +	migrate_disable();
> +	supported = __kvm_is_svm_supported();
> +	migrate_enable();
> +
> +	return supported;
> +}
> +
>  static int svm_check_processor_compat(void)
>  {
> -	if (!kvm_is_svm_supported())
> +	if (!__kvm_is_svm_supported())
>  		return -EIO;
>  
>  	return 0;
> -- 
> 2.40.1.606.ga4b1b128d6-goog
>
diff mbox series

Patch

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index b347173b4e29..cf5f3880751b 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -523,18 +523,20 @@  static void svm_init_osvw(struct kvm_vcpu *vcpu)
 		vcpu->arch.osvw.status |= 1;
 }
 
-static bool kvm_is_svm_supported(void)
+static bool __kvm_is_svm_supported(void)
 {
-	int cpu = raw_smp_processor_id();
+	int cpu = smp_processor_id();
+	struct cpuinfo_x86 *c = &cpu_data(cpu);
+
 	u64 vm_cr;
 
-	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
-	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) {
+	if (c->x86_vendor != X86_VENDOR_AMD &&
+	    c->x86_vendor != X86_VENDOR_HYGON) {
 		pr_err("CPU %d isn't AMD or Hygon\n", cpu);
 		return false;
 	}
 
-	if (!boot_cpu_has(X86_FEATURE_SVM)) {
+	if (!cpu_has(c, X86_FEATURE_SVM)) {
 		pr_err("SVM not supported by CPU %d\n", cpu);
 		return false;
 	}
@@ -553,9 +555,20 @@  static bool kvm_is_svm_supported(void)
 	return true;
 }
 
+static bool kvm_is_svm_supported(void)
+{
+	bool supported;
+
+	migrate_disable();
+	supported = __kvm_is_svm_supported();
+	migrate_enable();
+
+	return supported;
+}
+
 static int svm_check_processor_compat(void)
 {
-	if (!kvm_is_svm_supported())
+	if (!__kvm_is_svm_supported())
 		return -EIO;
 
 	return 0;