From 33f9c505ed5c83bd8a07877e5b4628308f4cc099 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Wed, 27 Feb 2008 16:06:57 +0200 Subject: [PATCH] KVM: VMX: Avoid rearranging switched guest msrs while they are loaded KVM tries to run as much as possible with the guest msrs loaded instead of host msrs, since switching msrs is very expensive. It also tries to minimize the number of msrs switched according to the guest mode; for example, MSR_LSTAR is needed only by long mode guests. This optimization is done by setup_msrs(). However, we must not change which msrs are switched while we are running with guest msr state: - switch to guest msr state - call setup_msrs(), removing some msrs from the list - switch to host msr state, leaving a few guest msrs loaded An easy way to trigger this is to kexec an x86_64 linux guest. Early during setup, the guest will switch EFER to not include SCE. KVM will stop saving MSR_LSTAR, and on the next msr switch it will leave the guest LSTAR loaded. The next host syscall will end up in a random location in the kernel. Fix by reloading the host msrs before changing the msr list. Signed-off-by: Avi Kivity --- arch/x86/kvm/vmx.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 61c2a3a8d20..94ea724638f 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -638,6 +638,7 @@ static void setup_msrs(struct vcpu_vmx *vmx) { int save_nmsrs; + vmx_load_host_state(vmx); save_nmsrs = 0; #ifdef CONFIG_X86_64 if (is_long_mode(&vmx->vcpu)) { -- 2.20.1