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Commit 6451e3ce authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Greg Kroah-Hartman
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KVM: VMX: Fix IBRS handling after vmexit 



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: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: default avatarSuleiman Souhlal <suleiman@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e6ac9561

arch/x86/kvm/vmx.c

+6 −2
Original line number Diff line number Diff line
@@ -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();