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KVM: nVMX: Truncate writes to vmcs.SYSENTER_EIP/ESP for 32-bit vCPU

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Explicitly truncate the data written to vmcs.SYSENTER_EIP/ESP on WRMSR
if the virtual CPU doesn't support 64-bit mode.  The SYSENTER address
fields in the VMCS are natural width, i.e. bits 63:32 are dropped if the
CPU doesn't support Intel 64 architectures.  This behavior is visible to
the guest after a VM-Exit/VM-Exit roundtrip, e.g. if the guest sets bits
63:32 in the actual MSR.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200428231025.12766-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-04-28 16:10:24 -07:00 committed by Paolo Bonzini
parent 551896e0e0
commit 2408500dfc
1 changed files with 16 additions and 2 deletions
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18
arch/x86/kvm/vmx/vmx.c
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@ -1943,6 +1943,16 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 0;
}
static u64 nested_vmx_truncate_sysenter_addr(struct kvm_vcpu *vcpu,
u64 data)
{
#ifdef CONFIG_X86_64
if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
return (u32)data;
#endif
return (unsigned long)data;
}
/*
* Writes msr value into the appropriate "register".
* Returns 0 on success, non-0 otherwise.
@ -1980,13 +1990,17 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vmcs_write32(GUEST_SYSENTER_CS, data);
break;
case MSR_IA32_SYSENTER_EIP:
if (is_guest_mode(vcpu))
if (is_guest_mode(vcpu)) {
data = nested_vmx_truncate_sysenter_addr(vcpu, data);
get_vmcs12(vcpu)->guest_sysenter_eip = data;
}
vmcs_writel(GUEST_SYSENTER_EIP, data);
break;
case MSR_IA32_SYSENTER_ESP:
if (is_guest_mode(vcpu))
if (is_guest_mode(vcpu)) {
data = nested_vmx_truncate_sysenter_addr(vcpu, data);
get_vmcs12(vcpu)->guest_sysenter_esp = data;
}
vmcs_writel(GUEST_SYSENTER_ESP, data);
break;
case MSR_IA32_DEBUGCTLMSR: