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KVM: VMX: Fix IBRS handling after vmexit

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For legacy IBRS to work, the IBRS bit needs to be always re-written
after vmexit, even if it's already on.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Josh Poimboeuf 2022-06-14 23:16:14 +02:00 • committed by Borislav Petkov
parent fc02735b14
commit bea7e31a5c
1 changed files with 6 additions and 1 deletions
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7
arch/x86/kvm/vmx/vmx.c
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@ -6844,8 +6844,13 @@ void noinstr vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx,
/*
* If the guest/host SPEC_CTRL values differ, restore the host value.
*
* For legacy IBRS, the IBRS bit always needs to be written after
* transitioning from a less privileged predictor mode, regardless of
* whether the guest/host values differ.
*/
if (vmx->spec_ctrl != hostval)
if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS) ||
vmx->spec_ctrl != hostval)
native_wrmsrl(MSR_IA32_SPEC_CTRL, hostval);
barrier_nospec();