linux-kernel - [tip:x86/pti] x86/bugs: Fix the AMD SSBD usage of the SPEC

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Date:   Tue, 3 Jul 2018 01:34:31 -0700
From:   tip-bot for Tom Lendacky <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, torvalds@...ux-foundation.org,
        konrad.wilk@...cle.com, bpetkov@...e.de,
        linux-kernel@...r.kernel.org, thomas.lendacky@....com,
        dwmw@...zon.co.uk, hpa@...or.com, peterz@...radead.org,
        tglx@...utronix.de
Subject: [tip:x86/pti] x86/bugs: Fix the AMD SSBD usage of the SPEC_CTRL MSR

Commit-ID:  612bc3b3d4be749f73a513a17d9b3ee1330d3487
Gitweb:     https://git.kernel.org/tip/612bc3b3d4be749f73a513a17d9b3ee1330d3487
Author:     Tom Lendacky <thomas.lendacky@....com>
AuthorDate: Mon, 2 Jul 2018 16:36:02 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 3 Jul 2018 09:45:48 +0200

x86/bugs: Fix the AMD SSBD usage of the SPEC_CTRL MSR

On AMD, the presence of the MSR_SPEC_CTRL feature does not imply that the
SSBD mitigation support should use the SPEC_CTRL MSR. Other features could
have caused the MSR_SPEC_CTRL feature to be set, while a different SSBD
mitigation option is in place.

Update the SSBD support to check for the actual SSBD features that will
use the SPEC_CTRL MSR.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Cc: Borislav Petkov <bpetkov@...e.de>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Fixes: 6ac2f49edb1e ("x86/bugs: Add AMD's SPEC_CTRL MSR usage")
Link: http://lkml.kernel.org/r/20180702213602.29202.33151.stgit@tlendack-t1.amdoffice.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/bugs.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 404df26b7de8..5c0ea39311fe 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -155,7 +155,8 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)
 		guestval |= guest_spec_ctrl & x86_spec_ctrl_mask;
 
 		/* SSBD controlled in MSR_SPEC_CTRL */
-		if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD))
+		if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
+		    static_cpu_has(X86_FEATURE_AMD_SSBD))
 			hostval |= ssbd_tif_to_spec_ctrl(ti->flags);
 
 		if (hostval != guestval) {
@@ -533,9 +534,10 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void)
 		 * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may
 		 * use a completely different MSR and bit dependent on family.
 		 */
-		if (!static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
+		if (!static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) &&
+		    !static_cpu_has(X86_FEATURE_AMD_SSBD)) {
 			x86_amd_ssb_disable();
-		else {
+		} else {
 			x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
 			x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
 			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);