From 91f85280b9b80852352fcad73d94ed29fafb88da Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 24 Oct 2017 18:12:31 +0200 Subject: [PATCH] x86: fix GS-base-dirty determination load_segments() writes the two MSRs in their "canonical" positions (GS_BASE for the user base, SHADOW_GS_BASE for the kernel one) and uses SWAPGS to switch them around if the incoming vCPU is in kernel mode. In order to not leave a stale kernel address in GS_BASE when the incoming guest is in user mode, the check on the outgoing vCPU needs to be dependent upon the mode it is currently in, rather than blindly looking at the user base. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper Release-acked-by: Julien Grall --- xen/arch/x86/domain.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index c28ac38fbe..735f45c133 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -1479,7 +1479,8 @@ static void save_segments(struct vcpu *v) if ( regs->gs & ~3 ) v->arch.pv_vcpu.gs_base_user = 0; } - if ( v->arch.pv_vcpu.gs_base_user ) + if ( v->arch.flags & TF_kernel_mode ? v->arch.pv_vcpu.gs_base_kernel + : v->arch.pv_vcpu.gs_base_user ) dirty_segment_mask |= DIRTY_GS_BASE_USER; this_cpu(dirty_segment_mask) = dirty_segment_mask; -- 2.30.2