Commit 2242cf21 authored Oct 03, 2022 by Josh Poimboeuf Committed by Greg Kroah-Hartman Oct 07, 2022

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: 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 51c71ed1

arch/x86/kvm/vmx/vmx.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -6571,8 +6571,13 @@ 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();