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KVM: SVM: Convert feature updates from CPUID to KVM cpu caps

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Use the recently introduced KVM CPU caps to propagate SVM-only (kernel)
settings to supported CPUID flags.

Note, there are a few subtleties:

  - Setting a flag based on a *different* feature is effectively
    emulation, and must be done at runtime via ->set_supported_cpuid().

  - CPUID 0x8000000A.EDX is a feature leaf that was previously not
    adjusted by kvm_cpu_cap_mask() because all features are hidden by
    default.

Opportunistically add a technically unnecessary break and fix an
indentation issue in svm_set_supported_cpuid().

No functional change intended.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-03-02 15:56:42 -08:00 committed by Paolo Bonzini
parent 66a6950f99
commit 9b58b9857f
2 changed files with 36 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/kvm/cpuid.c
View File

@ -370,6 +370,12 @@ void kvm_set_cpu_caps(void)
F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON)
);
/*
* Hide all SVM features by default, SVM will set the cap bits for
* features it emulates and/or exposes for L1.
*/
kvm_cpu_cap_mask(CPUID_8000_000A_EDX, 0);
kvm_cpu_cap_mask(CPUID_C000_0001_EDX,
F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |

44
arch/x86/kvm/svm.c
View File

@ -1367,6 +1367,23 @@ static void svm_hardware_teardown(void)
iopm_base = 0;
}
static __init void svm_set_cpu_caps(void)
{
kvm_set_cpu_caps();
/* CPUID 0x80000001 */
if (nested)
kvm_cpu_cap_set(X86_FEATURE_SVM);
/* CPUID 0x8000000A */
/* Support next_rip if host supports it */
if (boot_cpu_has(X86_FEATURE_NRIPS))
kvm_cpu_cap_set(X86_FEATURE_NRIPS);
if (npt_enabled)
kvm_cpu_cap_set(X86_FEATURE_NPT);
}
static __init int svm_hardware_setup(void)
{
int cpu;
@ -1479,7 +1496,7 @@ static __init int svm_hardware_setup(void)
pr_info("Virtual GIF supported\n");
}
kvm_set_cpu_caps();
svm_set_cpu_caps();
return 0;
@ -6035,13 +6052,17 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
APICV_INHIBIT_REASON_NESTED);
}
/*
* Vendor specific emulation must be handled via ->set_supported_cpuid(), not
* svm_set_cpu_caps(), as capabilities configured during hardware_setup() are
* masked against hardware/kernel support, i.e. they'd be lost.
*
* Note, setting a flag based on a *different* feature, e.g. setting VIRT_SSBD
* if LS_CFG_SSBD or AMD_SSBD is supported, is effectively emulation.
*/
static void svm_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
{
switch (entry->function) {
case 0x80000001:
if (nested)
cpuid_entry_set(entry, X86_FEATURE_SVM);
break;
case 0x80000008:
if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) ||
boot_cpu_has(X86_FEATURE_AMD_SSBD))
@ -6052,16 +6073,9 @@ static void svm_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
entry->ebx = 8; /* Lets support 8 ASIDs in case we add proper
ASID emulation to nested SVM */
entry->ecx = 0; /* Reserved */
entry->edx = 0; /* Per default do not support any
additional features */
/* Support next_rip if host supports it */
if (boot_cpu_has(X86_FEATURE_NRIPS))
cpuid_entry_set(entry, X86_FEATURE_NRIPS);
/* Support NPT for the guest if enabled */
if (npt_enabled)
cpuid_entry_set(entry, X86_FEATURE_NPT);
/* Note, 0x8000000A.EDX is managed via kvm_cpu_caps. */;
cpuid_entry_mask(entry, CPUID_8000_000A_EDX);
break;
}
}