linux-kernel - [PATCH 4.4 187/266] x86/bugs: Add AMDs variant of SSB

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Date:   Wed, 15 May 2019 12:54:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
        kvm@...r.kernel.org, andrew.cooper3@...rix.com,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Ben Hutchings <ben@...adent.org.uk>
Subject: [PATCH 4.4 187/266] x86/bugs: Add AMDs variant of SSB_NO

From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

commit 24809860012e0130fbafe536709e08a22b3e959e upstream.

The AMD document outlining the SSBD handling
124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
mentions that the CPUID 8000_0008.EBX[26] will mean that the
speculative store bypass disable is no longer needed.

A copy of this document is available at:
    https://bugzilla.kernel.org/show_bug.cgi?id=199889

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Janakarajan Natarajan <Janakarajan.Natarajan@....com>
Cc: kvm@...r.kernel.org
Cc: andrew.cooper3@...rix.com
Cc: Andy Lutomirski <luto@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Link: https://lkml.kernel.org/r/20180601145921.9500-2-konrad.wilk@oracle.com
[bwh: Backported to 4.4: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/include/asm/cpufeatures.h |    1 +
 arch/x86/kernel/cpu/common.c       |    3 ++-
 arch/x86/kvm/cpuid.c               |    2 +-
 3 files changed, 4 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -270,6 +270,7 @@
 #define X86_FEATURE_AMD_IBRS	(13*32+14) /* "" Indirect Branch Restricted Speculation */
 #define X86_FEATURE_AMD_STIBP	(13*32+15) /* "" Single Thread Indirect Branch Predictors */
 #define X86_FEATURE_VIRT_SSBD	(13*32+25) /* Virtualized Speculative Store Bypass Disable */
+#define X86_FEATURE_AMD_SSB_NO	(13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */
 
 /* Thermal and Power Management Leaf, CPUID level 0x00000006 (eax), word 14 */
 #define X86_FEATURE_DTHERM	(14*32+ 0) /* Digital Thermal Sensor */
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -904,7 +904,8 @@ static void __init cpu_set_bug_bits(stru
 		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
 
 	if (!x86_match_cpu(cpu_no_spec_store_bypass) &&
-	   !(ia32_cap & ARCH_CAP_SSB_NO))
+	   !(ia32_cap & ARCH_CAP_SSB_NO) &&
+	   !cpu_has(c, X86_FEATURE_AMD_SSB_NO))
 		setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);
 
 	if (ia32_cap & ARCH_CAP_IBRS_ALL)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -343,7 +343,7 @@ static inline int __do_cpuid_ent(struct
 
 	/* cpuid 0x80000008.ebx */
 	const u32 kvm_cpuid_8000_0008_ebx_x86_features =
-		F(AMD_IBPB) | F(AMD_IBRS) | F(VIRT_SSBD);
+		F(AMD_IBPB) | F(AMD_IBRS) | F(VIRT_SSBD) | F(AMD_SSB_NO);
 
 	/* cpuid 0xC0000001.edx */
 	const u32 kvm_supported_word5_x86_features =