From abbf8c99a9e12182c350e93cb808de4599a2f701 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Tue, 4 May 2021 10:17:21 -0700
Subject: [PATCH] KVM: x86: Emulate RDPID only if RDTSCP is supported
commit 85d0011264da24be08ae907d7f29983a597ca9b1 upstream.
Do not advertise emulation support for RDPID if RDTSCP is unsupported.
RDPID emulation subtly relies on MSR_TSC_AUX to exist in hardware, as
both vmx_get_msr() and svm_get_msr() will return an error if the MSR is
unsupported, i.e. ctxt->ops->get_msr() will fail and the emulator will
inject a #UD.
Note, RDPID emulation also relies on RDTSCP being enabled in the guest,
but this is a KVM bug and will eventually be fixed.
Fixes: fb6d4d340e05 ("KVM: x86: emulate RDPID")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-3-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/cpuid.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 62157b1000f08..56a62d555e924 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -572,7 +572,8 @@ static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func)
case 7:
entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
entry->eax = 0;
- entry->ecx = F(RDPID);
+ if (kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
+ entry->ecx = F(RDPID);
++array->nent;
default:
break;
--
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