From c4dd58f0cf23cdf119bbccedfb8c24435fc6f3ab Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 16 Mar 2018 17:27:36 +0100 Subject: [PATCH] x86: correct EFLAGS.IF in SYSENTER frame Commit 9d1d31ad94 ("x86: slightly reduce Meltdown band-aid overhead") moved the STI past the PUSHF. While this isn't an active problem (as we force EFLAGS.IF to 1 before exiting to guest context), let's not risk internal confusion by finding a PV guest frame with interrupts apparently off. Signed-off-by: Jan Beulich Acked-by: Andrew Cooper --- xen/arch/x86/x86_64/entry.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index f6ba31c4e2..e3d18daba8 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -281,6 +281,8 @@ GLOBAL(sysenter_eflags_saved) /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */ GET_STACK_END(bx) + /* PUSHF above has saved EFLAGS.IF clear (the caller had it set). */ + orl $X86_EFLAGS_IF, UREGS_eflags(%rsp) mov STACK_CPUINFO_FIELD(xen_cr3)(%rbx), %rcx neg %rcx jz .Lsyse_cr3_okay -- 2.30.2