korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-12-23 19:14:30 +08:00
Code Issues Packages Projects Releases Wiki Activity

KVM: x86: do not modify masked bits of shared MSRs

Browse Source 
"Shared MSRs" are guest MSRs that are written to the host MSRs but
keep their value until the next return to userspace.  They support
a mask, so that some bits keep the host value, but this mask is
only used to skip an unnecessary MSR write and the value written
to the MSR is always the guest MSR.

Fix this and, while at it, do not update smsr->values[slot].curr if
for whatever reason the wrmsr fails.  This should only happen due to
reserved bits, so the value written to smsr->values[slot].curr
will not match when the user-return notifier and the host value will
always be restored.  However, it is untidy and in rare cases this
can actually avoid spurious WRMSRs on return to userspace.

Cc: stable@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Tested-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2019-11-18 12:23:00 -05:00
parent cbbaa2727a
commit de1fca5d6e
1 changed files with 3 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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

@ -300,13 +300,14 @@ int kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
int err;
if (((value ^ smsr->values[slot].curr) & mask) == 0)
value = (value & mask) | (smsr->values[slot].host & ~mask);
if (value == smsr->values[slot].curr)
return 0;
smsr->values[slot].curr = value;
err = wrmsrl_safe(shared_msrs_global.msrs[slot], value);
if (err)
return 1;
smsr->values[slot].curr = value;
if (!smsr->registered) {
smsr->urn.on_user_return = kvm_on_user_return;
user_return_notifier_register(&smsr->urn);