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Re: [Xen-devel] [PATCH 2/2] x86/xen: use capabilities instead of fake cpuid values
On 02/17/2017 09:19 AM, Juergen Gross wrote:
On 17/02/17 15:05, Boris Ostrovsky wrote:On 02/17/2017 02:36 AM, Juergen Gross wrote:When running as pv domain xen_cpuid() is being used instead of native_cpuid(). In xen_cpuid() the aperf/mperf feature is indicated as not being present by special casing the related cpuid leaf. Instead of delivering fake cpuid values clear the cpu capability bit for aperf/mperf instead. Signed-off-by: Juergen Gross <jgross@xxxxxxxx> --- arch/x86/xen/enlighten.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 83399ce..0eebb75 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -301,9 +301,6 @@ xen_running_on_version_or_later(unsigned int major, unsigned int minor) return false; } -#define CPUID_THERM_POWER_LEAF 6 -#define APERFMPERF_PRESENT 0 - static __read_mostly unsigned int cpuid_leaf1_edx_mask = ~0; static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0; @@ -337,11 +334,6 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx, *dx = cpuid_leaf5_edx_val; return; - case CPUID_THERM_POWER_LEAF: - /* Disabling APERFMPERF for kernel usage */ - maskecx = ~(1 << APERFMPERF_PRESENT); - break; -But now APERF/MPERF will be reported as supported by CPUID, won't it?Yes. But this shouldn't be a problem as the kernel is always testing X86_FEATURE_APERFMPERF for testing the support.
But X86_FEATURE_APERFMPERF cap is set based on CPUID query. -boris
case 0xb: /* Suppress extended topology stuff */ maskebx = 0; @@ -462,6 +454,9 @@ static void __init xen_init_cpuid_mask(void) if (xen_check_mwait()) cpuid_leaf1_ecx_set_mask = (1 << (X86_FEATURE_MWAIT % 32)); + /* Disable APERFMPERF feature. */ + setup_clear_cpu_cap(X86_FEATURE_APERFMPERF); + /* Disable DCA feature. */ setup_clear_cpu_cap(X86_FEATURE_DCA);I think both of those can go to xen_set_cpu_features().Okay. I'll move them. I think we can convert some of the remaining cpuid bit modifications to cpu capabilities as well. Juergen
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