| Message ID | 20200402101902.28234-2-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/ucode: Cleanup part 5/n | expand |
On 02.04.2020 12:18, Andrew Cooper wrote: > The CPUID instruction is expensive. No point executing it twice when once > will do fine. > > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> albeit ... > --- a/xen/arch/x86/cpu/microcode/intel.c > +++ b/xen/arch/x86/cpu/microcode/intel.c > @@ -121,14 +121,12 @@ static int collect_cpu_info(struct cpu_signature *csig) > > memset(csig, 0, sizeof(*csig)); > > - csig->sig = cpuid_eax(0x00000001); > - > rdmsrl(MSR_IA32_PLATFORM_ID, msr_content); > csig->pf = 1 << ((msr_content >> 50) & 7); > > wrmsrl(MSR_IA32_UCODE_REV, 0x0ULL); > /* As documented in the SDM: Do a CPUID 1 here */ > - cpuid_eax(1); > + csig->sig = cpuid_eax(1); ... with this, perhaps make the title say "remove one CPUID ..." or some such? Jan
diff --git a/xen/arch/x86/cpu/microcode/intel.c b/xen/arch/x86/cpu/microcode/intel.c index 72bd1ad0bc..f1e64e188b 100644 --- a/xen/arch/x86/cpu/microcode/intel.c +++ b/xen/arch/x86/cpu/microcode/intel.c @@ -121,14 +121,12 @@ static int collect_cpu_info(struct cpu_signature *csig) memset(csig, 0, sizeof(*csig)); - csig->sig = cpuid_eax(0x00000001); - rdmsrl(MSR_IA32_PLATFORM_ID, msr_content); csig->pf = 1 << ((msr_content >> 50) & 7); wrmsrl(MSR_IA32_UCODE_REV, 0x0ULL); /* As documented in the SDM: Do a CPUID 1 here */ - cpuid_eax(1); + csig->sig = cpuid_eax(1); /* get the current revision from MSR 0x8B */ rdmsrl(MSR_IA32_UCODE_REV, msr_content);
The CPUID instruction is expensive. No point executing it twice when once will do fine. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Wei Liu <wl@xen.org> CC: Roger Pau Monné <roger.pau@citrix.com> --- xen/arch/x86/cpu/microcode/intel.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)