Commit-ID: 20ffa1caecca4db8f79fe665acdeaa5af815a24d Gitweb: https://git.kernel.org/tip/20ffa1caecca4db8f79fe665acdeaa5af815a24d Author: David Woodhouse <d...@amazon.co.uk> AuthorDate: Thu, 25 Jan 2018 16:14:15 +0000 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Fri, 26 Jan 2018 15:53:18 +0100
x86/speculation: Add basic IBPB (Indirect Branch Prediction Barrier) support Expose indirect_branch_prediction_barrier() for use in subsequent patches. [ tglx: Add IBPB status to spectre_v2 sysfs file ] Co-developed-by: KarimAllah Ahmed <karah...@amazon.de> Signed-off-by: KarimAllah Ahmed <karah...@amazon.de> Signed-off-by: David Woodhouse <d...@amazon.co.uk> Cc: gno...@lxorguk.ukuu.org.uk Cc: a...@linux.intel.com Cc: ashok....@intel.com Cc: dave.han...@intel.com Cc: ar...@linux.intel.com Cc: torva...@linux-foundation.org Cc: pet...@infradead.org Cc: b...@alien8.de Cc: pbonz...@redhat.com Cc: tim.c.c...@linux.intel.com Cc: gre...@linux-foundation.org Link: https://lkml.kernel.org/r/1516896855-7642-8-git-send-email-d...@amazon.co.uk --- arch/x86/include/asm/cpufeatures.h | 2 ++ arch/x86/include/asm/nospec-branch.h | 13 +++++++++++++ arch/x86/kernel/cpu/bugs.c | 10 +++++++++- 3 files changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index ae3212f..07934b2 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -210,6 +210,8 @@ #define X86_FEATURE_MBA ( 7*32+18) /* Memory Bandwidth Allocation */ #define X86_FEATURE_RSB_CTXSW ( 7*32+19) /* Fill RSB on context switches */ +#define X86_FEATURE_IBPB ( 7*32+21) /* Indirect Branch Prediction Barrier enabled*/ + /* Virtualization flags: Linux defined, word 8 */ #define X86_FEATURE_TPR_SHADOW ( 8*32+ 0) /* Intel TPR Shadow */ #define X86_FEATURE_VNMI ( 8*32+ 1) /* Intel Virtual NMI */ diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 4ad4108..34e384c 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -218,5 +218,18 @@ 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 /* __NOSPEC_BRANCH_H__ */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 4a39d7b..bac7a35 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -263,6 +263,13 @@ 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 @@ -292,7 +299,8 @@ ssize_t cpu_show_spectre_v2(struct device *dev, 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_bad_module ? " - vulnerable module loaded" : ""); } #endif
