3.16.56-rc1 review patch. If anyone has any objections, please let me know.
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From: David Woodhouse dwmw@amazon.co.uk
commit 2961298efe1ea1b6fc0d7ee8b76018fa6c0bcef2 upstream.
We want to expose the hardware features simply in /proc/cpuinfo as "ibrs", "ibpb" and "stibp". Since AMD has separate CPUID bits for those, use them as the user-visible bits.
When the Intel SPEC_CTRL bit is set which indicates both IBRS and IBPB capability, set those (AMD) bits accordingly. Likewise if the Intel STIBP bit is set, set the AMD STIBP that's used for the generic hardware capability.
Hide the rest from /proc/cpuinfo by putting "" in the comments. Including RETPOLINE and RETPOLINE_AMD which shouldn't be visible there. There are patches to make the sysfs vulnerabilities information non-readable by non-root, and the same should apply to all information about which mitigations are actually in use. Those *shouldn't* appear in /proc/cpuinfo.
The feature bit for whether IBPB is actually used, which is needed for ALTERNATIVEs, is renamed to X86_FEATURE_USE_IBPB.
Originally-by: Borislav Petkov bp@suse.de Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: ak@linux.intel.com Cc: dave.hansen@intel.com Cc: karahmed@amazon.de Cc: arjan@linux.intel.com Cc: torvalds@linux-foundation.org Cc: peterz@infradead.org Cc: bp@alien8.de Cc: pbonzini@redhat.com Cc: tim.c.chen@linux.intel.com Cc: gregkh@linux-foundation.org Link: https://lkml.kernel.org/r/1517070274-12128-2-git-send-email-dwmw@amazon.co.u... [bwh: For 3.16, just apply the part that hides fake CPU feature bits] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -187,10 +187,10 @@ #define X86_FEATURE_HW_PSTATE (7*32+ 8) /* AMD HW-PState */ #define X86_FEATURE_PROC_FEEDBACK (7*32+ 9) /* AMD ProcFeedbackInterface */ #define X86_FEATURE_INVPCID_SINGLE (7*32+10) /* Effectively INVPCID && CR4.PCIDE=1 */ -#define X86_FEATURE_RSB_CTXSW (7*32+11) /* Fill RSB on context switches */ +#define X86_FEATURE_RSB_CTXSW (7*32+11) /* "" Fill RSB on context switches */
-#define X86_FEATURE_RETPOLINE (7*32+29) /* Generic Retpoline mitigation for Spectre variant 2 */ -#define X86_FEATURE_RETPOLINE_AMD (7*32+30) /* AMD Retpoline mitigation for Spectre variant 2 */ +#define X86_FEATURE_RETPOLINE (7*32+29) /* "" Generic Retpoline mitigation for Spectre variant 2 */ +#define X86_FEATURE_RETPOLINE_AMD (7*32+30) /* "" AMD Retpoline mitigation for Spectre variant 2 */ /* Because the ALTERNATIVE scheme is for members of the X86_FEATURE club... */ #define X86_FEATURE_KAISER (7*32+31) /* "" CONFIG_PAGE_TABLE_ISOLATION w/o nokaiser */