3.16.57-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: David Woodhouse dwmw@amazon.co.uk
commit 20ffa1caecca4db8f79fe665acdeaa5af815a24d upstream.
Expose indirect_branch_prediction_barrier() for use in subsequent patches.
[ tglx: Add IBPB status to spectre_v2 sysfs file ]
Co-developed-by: KarimAllah Ahmed karahmed@amazon.de Signed-off-by: KarimAllah Ahmed karahmed@amazon.de Signed-off-by: David Woodhouse dwmw@amazon.co.uk Cc: gnomes@lxorguk.ukuu.org.uk Cc: ak@linux.intel.com Cc: ashok.raj@intel.com Cc: dave.hansen@intel.com 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/1516896855-7642-8-git-send-email-dwmw@amazon.co.uk Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [bwh: Backported to 3.16: - Renumber the feature bit - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/x86/include/asm/cpufeature.h | 2 ++ arch/x86/include/asm/nospec-branch.h | 13 +++++++++++++ arch/x86/kernel/cpu/bugs.c | 10 +++++++++- 3 files changed, 24 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -189,6 +189,8 @@ #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_IBPB (7*32+12) /* Indirect Branch Prediction Barrier enabled*/ + #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... */ --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -194,5 +194,18 @@ static inline void vmexit_fill_RSB(void) #endif }
+static inline void indirect_branch_prediction_barrier(void) +{ + asm volatile(ALTERNATIVE("", + "movl %[msr], %%ecx\n\t" + "movl %[val], %%eax\n\t" + "movl $0, %%edx\n\t" + "wrmsr", + X86_FEATURE_IBPB) + : : [msr] "i" (MSR_IA32_PRED_CMD), + [val] "i" (PRED_CMD_IBPB) + : "eax", "ecx", "edx", "memory"); +} + #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_NOSPEC_BRANCH_H_ */ --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -358,6 +358,13 @@ retpoline_auto: setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW); pr_info("Filling RSB on context switch\n"); } + + /* Initialize Indirect Branch Prediction Barrier if supported */ + if (boot_cpu_has(X86_FEATURE_SPEC_CTRL) || + boot_cpu_has(X86_FEATURE_AMD_PRED_CMD)) { + setup_force_cpu_cap(X86_FEATURE_IBPB); + pr_info("Enabling Indirect Branch Prediction Barrier\n"); + } }
#undef pr_fmt @@ -387,7 +394,8 @@ ssize_t cpu_show_spectre_v2(struct devic if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) return sprintf(buf, "Not affected\n");
- return sprintf(buf, "%s%s\n", spectre_v2_strings[spectre_v2_enabled], + return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled], + boot_cpu_has(X86_FEATURE_IBPB) ? ", IPBP" : "", spectre_v2_module_string()); } #endif