From a41bba43a7f913b1e952a8693af825ad315ee2d1 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Thu, 9 Apr 2026 10:07:32 +0100 Subject: [PATCH] x86/pv: Adjust the save_segments() comment regarding MSR_GS_SHADOW This is slightly stale mentioning SWAPGS and not LKGS. However, take the opportunity to make the comment more general and less likely to bitrot. It would be a serious vulnerability for operating systems generally if CPL3 could modify GS_SHADOW at all. No functional change. Signed-off-by: Andrew Cooper Reviewed-by: Teddy Astie --- xen/arch/x86/domain.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 1d458f1372..4252339978 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -1951,9 +1951,8 @@ static void load_segments(struct vcpu *n) * changes to bases can also be made with the WR{FS,GS}BASE instructions, when * enabled. * - * Guests however cannot use SWAPGS, so there is no mechanism to modify the - * inactive GS base behind Xen's back. Therefore, Xen's copy of the inactive - * GS base is still accurate, and doesn't need reading back from hardware. + * Guests cannot modify the inactive GS base behind Xen's back. Therefore + * Xen's copy is still accurate and doesn't need reading back. * * Under FRED, hardware automatically swaps GS for us, so SHADOW_GS is the * active GS from the guest's point of view.