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Subject[PATCH 8/8] KVM: x86: add SPEC_CTRL and IBPB_SUPPORT to MSR and CPUID lists
Date
Expose them to userspace, now that guests can use them.
I am not adding cpufeatures here to avoid having a kernel
that shows spec_ctrl in /proc/cpuinfo and actually has no
support whatsoever for IBRS/IBPB. Keep the ugly special-casing
for now, and clean it up once the generic arch/x86/ code
learns about them.

Reviewed-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/cpuid.c | 24 +++++++++++++++++++++---
arch/x86/kvm/x86.c | 1 +
2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 767af697c20c..5f43a5940275 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -397,7 +397,12 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,

/* cpuid 7.0.edx*/
const u32 kvm_cpuid_7_0_edx_x86_features =
- KF(AVX512_4VNNIW) | KF(AVX512_4FMAPS);
+ KF(AVX512_4VNNIW) | KF(AVX512_4FMAPS) |
+ KF(SPEC_CTRL) | KF(STIBP);
+
+ /* cpuid 0x80000008.edx */
+ const u32 kvm_cpuid_80000008_ebx_x86_features =
+ KF(IBPB_SUPPORT);

/* all calls to cpuid_count() should be made on the same cpu */
get_cpu();
@@ -483,7 +488,14 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
entry->ecx &= ~F(PKU);
entry->edx &= kvm_cpuid_7_0_edx_x86_features;
- entry->edx &= get_scattered_cpuid_leaf(7, 0, CPUID_EDX);
+ /*
+ * FIXME: the special casing of SPEC_CTRL and STIBP
+ * can be removed once they become regular
+ * cpufeatures.
+ */
+ entry->edx &= (
+ get_scattered_cpuid_leaf(7, 0, CPUID_EDX) |
+ KF(SPEC_CTRL) | KF(STIBP));
} else {
entry->ebx = 0;
entry->ecx = 0;
@@ -651,7 +663,13 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
if (!g_phys_as)
g_phys_as = phys_as;
entry->eax = g_phys_as | (virt_as << 8);
- entry->ebx = entry->edx = 0;
+ /*
+ * FIXME: mask against cpufeatures, with
+ * get_scattered_cpuid_leaf(0x80000008, 0, CPUID_EBX),
+ * once IBPB_SUPPORT becomes a regular cpufeature.
+ */
+ entry->ebx &= kvm_cpuid_80000008_ebx_x86_features;
+ entry->edx = 0;
break;
}
case 0x80000019:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index daa1918031df..4abb37d9f4d8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1032,6 +1032,7 @@ unsigned int kvm_get_pt_addr_cnt(void)
MSR_IA32_RTIT_ADDR1_A, MSR_IA32_RTIT_ADDR1_B,
MSR_IA32_RTIT_ADDR2_A, MSR_IA32_RTIT_ADDR2_B,
MSR_IA32_RTIT_ADDR3_A, MSR_IA32_RTIT_ADDR3_B,
+ MSR_IA32_SPEC_CTRL,
};

static unsigned num_msrs_to_save;
--
1.8.3.1

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