4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Ashok Raj <ashok....@intel.com> commit c182d2b7d0ca48e0d6ff16f7d883161238c447ed upstream. After updating microcode on one of the threads of a core, the other thread sibling automatically gets the update since the microcode resources on a hyperthreaded core are shared between the two threads. Check the microcode revision on the CPU before performing a microcode update and thus save us the WRMSR 0x79 because it is a particularly expensive operation. [ Borislav: Massage changelog and coding style. ] Signed-off-by: Ashok Raj <ashok....@intel.com> Signed-off-by: Borislav Petkov <b...@suse.de> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Tested-by: Tom Lendacky <thomas.lenda...@amd.com> Tested-by: Ashok Raj <ashok....@intel.com> Cc: Arjan Van De Ven <arjan.van.de....@intel.com> Link: http://lkml.kernel.org/r/1519352533-15992-2-git-send-email-ashok....@intel.com Link: https://lkml.kernel.org/r/20180228102846.13447-3...@alien8.de Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/x86/kernel/cpu/microcode/intel.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -589,6 +589,17 @@ static int apply_microcode_early(struct if (!mc) return 0; + /* + * Save us the MSR write below - which is a particular expensive + * operation - when the other hyperthread has updated the microcode + * already. + */ + rev = intel_get_microcode_revision(); + if (rev >= mc->hdr.rev) { + uci->cpu_sig.rev = rev; + return UCODE_OK; + } + /* write microcode via MSR 0x79 */ native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits); @@ -776,7 +787,7 @@ static enum ucode_state apply_microcode_ { struct microcode_intel *mc; struct ucode_cpu_info *uci; - struct cpuinfo_x86 *c; + struct cpuinfo_x86 *c = &cpu_data(cpu); static int prev_rev; u32 rev; @@ -793,6 +804,18 @@ static enum ucode_state apply_microcode_ return UCODE_NFOUND; } + /* + * Save us the MSR write below - which is a particular expensive + * operation - when the other hyperthread has updated the microcode + * already. + */ + rev = intel_get_microcode_revision(); + if (rev >= mc->hdr.rev) { + uci->cpu_sig.rev = rev; + c->microcode = rev; + return UCODE_OK; + } + /* write microcode via MSR 0x79 */ wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits); @@ -813,8 +836,6 @@ static enum ucode_state apply_microcode_ prev_rev = rev; } - c = &cpu_data(cpu); - uci->cpu_sig.rev = rev; c->microcode = rev;
