From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Date: Mon, 8 Jan 2018 23:30:50 +0000 (-0500)
Subject: x86/IBRS: Save current status of MSR_IA32_SPEC_CTRL
X-Git-Tag: v4.1.12-124.31.3~1287
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=0d4d8920d828d4ab95897a83bc6d8f4c89d6a5ff;p=users%2Fjedix%2Flinux-maple.git

x86/IBRS: Save current status of MSR_IA32_SPEC_CTRL

... otherwise we are restoring garbage and the MSR only allows
writes to two lower bits, causing a #GPF is other bits are set

While at it, also stuff RSB, which we typically do before enabling
IBRS

Orabug: 27365419

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>
---

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index d52ec3c33b41..ed037398a2ad 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1996,6 +1996,8 @@ end_repeat_nmi:
 	DEFAULT_FRAME 0				/* XXX: Do we need this? */
 
 	/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
+	STUFF_RSB
+	ENABLE_IBRS_SAVE_AND_CLOBBER save_reg=%r13d
 	call do_nmi
 	RESTORE_IBRS_CLOBBER save_reg=%r13d
 #ifdef CONFIG_PAGE_TABLE_ISOLATION