4.15-stable review patch. If anyone has any objections, please let me know.
------------------ From: Borislav Petkov b...@suse.de commit 64e16720ea0879f8ab4547e3b9758936d483909b Make it all a function which does the WRMSR instead of having a hairy inline asm. [dwmw2: export it, fix CONFIG_RETPOLINE issues] Signed-off-by: Borislav Petkov <b...@suse.de> Signed-off-by: David Woodhouse <d...@amazon.co.uk> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: a...@linux.intel.com Cc: dave.han...@intel.com Cc: karah...@amazon.de 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/1517070274-12128-4-git-send-email-d...@amazon.co.uk Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/x86/include/asm/nospec-branch.h | 13 ++++--------- arch/x86/include/asm/processor.h | 3 +++ arch/x86/kernel/cpu/bugs.c | 6 ++++++ 3 files changed, 13 insertions(+), 9 deletions(-) --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -164,15 +164,10 @@ static inline void vmexit_fill_RSB(void) 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_USE_IBPB) - : : [msr] "i" (MSR_IA32_PRED_CMD), - [val] "i" (PRED_CMD_IBPB) - : "eax", "ecx", "edx", "memory"); + alternative_input("", + "call __ibp_barrier", + X86_FEATURE_USE_IBPB, + ASM_NO_INPUT_CLOBBER("eax", "ecx", "edx", "memory")); } #endif /* __ASSEMBLY__ */ --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -971,4 +971,7 @@ bool xen_set_default_idle(void); void stop_this_cpu(void *dummy); void df_debug(struct pt_regs *regs, long error_code); + +void __ibp_barrier(void); + #endif /* _ASM_X86_PROCESSOR_H */ --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -311,3 +311,9 @@ ssize_t cpu_show_spectre_v2(struct devic spectre_v2_module_string()); } #endif + +void __ibp_barrier(void) +{ + __wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0); +} +EXPORT_SYMBOL_GPL(__ibp_barrier);
