From: "Jan Beulich" <JBeulich@suse.com>
To: xen-devel <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: [PATCH] x86: correct EFLAGS.IF in SYSENTER frame
Date: Fri, 16 Mar 2018 08:13:35 -0600 [thread overview]
Message-ID: <5AABDF1F02000078001B2D98@prv-mh.provo.novell.com> (raw)
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 <jbeulich@suse.com>
--- 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
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next reply other threads:[~2018-03-16 14:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-16 14:13 Jan Beulich [this message]
2018-03-16 14:29 ` [PATCH] x86: correct EFLAGS.IF in SYSENTER frame Andrew Cooper
2018-03-16 15:04 ` Jan Beulich
2018-03-16 15:42 ` Andrew Cooper
2018-03-16 16:26 ` Jan Beulich
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