| From 5104d7ffcf24749939bea7fdb5378d186473f890 Mon Sep 17 00:00:00 2001 |
| From: Sean Christopherson <seanjc@google.com> |
| Date: Tue, 4 May 2021 10:17:24 -0700 |
| Subject: KVM: VMX: Disable preemption when probing user return MSRs |
| |
| From: Sean Christopherson <seanjc@google.com> |
| |
| 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> |
| --- |
| arch/x86/include/asm/kvm_host.h | 1 + |
| arch/x86/kvm/vmx/vmx.c | 5 +---- |
| arch/x86/kvm/x86.c | 16 ++++++++++++++++ |
| 3 files changed, 18 insertions(+), 4 deletions(-) |
| |
| --- a/arch/x86/include/asm/kvm_host.h |
| +++ b/arch/x86/include/asm/kvm_host.h |
| @@ -1668,6 +1668,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, uns |
| 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); |
| --- a/arch/x86/kvm/vmx/vmx.c |
| +++ b/arch/x86/kvm/vmx/vmx.c |
| @@ -6864,12 +6864,9 @@ static int vmx_create_vcpu(struct kvm_vc |
| |
| 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; |
| --- a/arch/x86/kvm/x86.c |
| +++ b/arch/x86/kvm/x86.c |
| @@ -322,6 +322,22 @@ static void kvm_on_user_return(struct us |
| } |
| } |
| |
| +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); |