diff mbox series

[3.16,220/366] x86/bugs: Add AMD's variant of SSB_NO

Message ID lsq.1541965745.326257398@decadent.org.uk (mailing list archive)
State New, archived
Headers show
Series None | expand

Commit Message

Ben Hutchings Nov. 11, 2018, 7:49 p.m. UTC 
3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.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@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Cc: kvm@vger.kernel.org
Cc: andrew.cooper3@citrix.com
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lkml.kernel.org/r/20180601145921.9500-2-konrad.wilk@oracle.com
[bwh: Backported to 3.16:
 - The feature bit is in feature word 11
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 arch/x86/include/asm/cpufeature.h | 1 +
 arch/x86/kernel/cpu/common.c      | 3 ++-
 arch/x86/kvm/cpuid.c              | 2 +-
 3 files changed, 4 insertions(+), 2 deletions(-)
diff mbox series

Patch

--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -257,6 +257,7 @@ 
 #define X86_FEATURE_AMD_IBRS		(11*32+14) /* "" Indirect Branch Restricted Speculation */
 #define X86_FEATURE_AMD_STIBP		(11*32+15) /* "" Single Thread Indirect Branch Predictors */
 #define X86_FEATURE_VIRT_SSBD		(11*32+25) /* Virtualized Speculative Store Bypass Disable */
+#define X86_FEATURE_AMD_SSB_NO		(11*32+26) /* "" Speculative Store Bypass is fixed in hardware. */
 
 /*
  * BUG word(s)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -865,7 +865,8 @@  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 (x86_match_cpu(cpu_no_speculation))
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -302,7 +302,7 @@  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 =