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

Sean Christopherson
2023-05-12T23:52:31Z

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(-)

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