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KVM: VMX: Disable preemption when probing user return MSRs

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commit 5104d7ffcf24749939bea7fdb5378d186473f890 upstream.

Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
the MSR holds a different value per logical CPU, the WRMSR could corrupt
the host's value if KVM is preempted between the RDMSR and WRMSR, and
then rescheduled on a different CPU.

Opportunistically land the helper in common x86, SVM will use the helper
in a future commit.

Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation")
Cc: stable@vger.kernel.org
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-6-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2021-05-04 10:17:24 -07:00 committed by Greg Kroah-Hartman
parent 79abde761e
commit 31f29749ee
3 changed files with 18 additions and 4 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -1668,6 +1668,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
unsigned long icr, int op_64_bit);
void kvm_define_user_return_msr(unsigned index, u32 msr);
int kvm_probe_user_return_msr(u32 msr);
int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask);
u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc);

5
arch/x86/kvm/vmx/vmx.c
View File

@ -6864,12 +6864,9 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
for (i = 0; i < ARRAY_SIZE(vmx_uret_msrs_list); ++i) {
u32 index = vmx_uret_msrs_list[i];
u32 data_low, data_high;
int j = vmx->nr_uret_msrs;
if (rdmsr_safe(index, &data_low, &data_high) < 0)
continue;
if (wrmsr_safe(index, data_low, data_high) < 0)
if (kvm_probe_user_return_msr(index))
continue;
vmx->guest_uret_msrs[j].slot = i;

16
arch/x86/kvm/x86.c
View File

@ -322,6 +322,22 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
}
}
int kvm_probe_user_return_msr(u32 msr)
{
u64 val;
int ret;
preempt_disable();
ret = rdmsrl_safe(msr, &val);
if (ret)
goto out;
ret = wrmsrl_safe(msr, val);
out:
preempt_enable();
return ret;
}
EXPORT_SYMBOL_GPL(kvm_probe_user_return_msr);
void kvm_define_user_return_msr(unsigned slot, u32 msr)
{
BUG_ON(slot >= KVM_MAX_NR_USER_RETURN_MSRS);