On 3/15/23 11:16 PM, Sean Christopherson wrote:
On Wed, Mar 15, 2023, Daniil Tatianin wrote:...and return KVM_MSR_RET_INVALID otherwise. Found by Linux Verification Center (linuxtesting.org) with the SVACE static analysis tool. Fixes: cd28325249a1 ("KVM: VMX: support MSR_IA32_ARCH_CAPABILITIES as a feature MSR") Signed-off-by: Daniil Tatianin <d-tatianin@xxxxxxxxxxxxxx> --- arch/x86/kvm/x86.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7713420abab0..7de6939fc371 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1661,7 +1661,8 @@ static int kvm_get_msr_feature(struct kvm_msr_entry *msr) msr->data = kvm_caps.supported_perf_cap; break; case MSR_IA32_UCODE_REV: - rdmsrl_safe(msr->index, &msr->data); + if (rdmsrl_safe(msr->index, &msr->data)) + return KVM_MSR_RET_INVALID;This is unnecessary and would arguably break KVM's ABI. KVM unconditionally emulates MSR_IA32_UCODE_REV in software and rdmsrl_safe() zeros the result on a fault (see ex_handler_msr()). '0' is a legitimate ucode revid and a reasonable fallback for a theoretical (virtual) CPU that doesn't support the MSR.
I see, thanks for the explanation!
