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KVM: VMX: Fix IBRS handling after vmexit

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commit bea7e31a5caccb6fe8ed989c065072354f0ecb52 upstream.

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>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf 2022-11-17 18:19:44 +09:00 committed by Greg Kroah-Hartman
parent e6ac956177
commit 6451e3ce91
1 changed files with 6 additions and 2 deletions
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8
arch/x86/kvm/vmx.c
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@ -10770,9 +10770,13 @@ u64 __always_inline vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx)
guestval = __rdmsr(MSR_IA32_SPEC_CTRL);
/*
* 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 (guestval != hostval)
if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS) ||
guestval != hostval)
native_wrmsrl(MSR_IA32_SPEC_CTRL, hostval);
barrier_nospec();