This is a note to let you know that I've just added the patch titled
KVM: VMX: Disable preemption when probing user return MSRs
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-vmx-disable-preemption-when-probing-user-return-msrs.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5104d7ffcf24749939bea7fdb5378d186473f890 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Tue, 4 May 2021 10:17:24 -0700
Subject: KVM: VMX: Disable preemption when probing user return MSRs
From: Sean Christopherson <seanjc@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Cc: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-Id: <20210504171734.1434054-6-seanjc@xxxxxxxxxx>
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are
queue-5.10/kvm-vmx-disable-preemption-when-probing-user-return-msrs.patch
queue-5.10/kvm-vmx-do-not-advertise-rdpid-if-enable_rdtscp-control-is-unsupported.patch
queue-5.10/crypto-ccp-free-sev-device-if-sev-init-fails.patch
queue-5.10/kvm-x86-mmu-remove-the-defunct-update_pte-paging-hook.patch
queue-5.10/kvm-lapic-accurately-guarantee-busy-wait-for-timer-t.patch
queue-5.10/kvm-x86-move-rdpid-emulation-intercept-to-its-own-enum.patch
queue-5.10/kvm-x86-emulate-rdpid-only-if-rdtscp-is-supported.patch
