[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH]ACPI: re-enable mwait for xen cpuidle
Think about it some more: Since this is about partial enabling of MONITOR/WAIT, just to get C-state info to Xen -- i.e., something a bit hacky anyway -- the right answer is for Linux to lie to itself and your 2nd patch attempt is best. I would think of Xen advertising the fature to dom0 via CPUID as meaning that the guest can use it as a 1st-class feature itself, which is not the case. -- Keir On 02/04/2010 15:27, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote: > It also has wider impact, including questionable effect on existing dom0 > kernels which have never been tested with MONITOR/MWAIT present in > virtualised CPUID. I'm not sure about making this change even in current > xen-unstable (but not dead against it), and there's no chance for 4.0 and > 3.4 branches. > > -- Keir > > On 02/04/2010 14:41, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote: > >> The 3rd choice: don't clear MWAIT feature in xen. This should be the best >> choice. >> >> Jimmy >> >> X86: re-enable mwait for xen cpuidle >> >> Xen hypervisor doesn't export mwait feature to dom0, but latest Linux kernel >> start to check this feature while initializing _PDC object. Pass the MWAIT >> feature to dom0 to let dom0 got & pass to xen correct C state info. >> >> Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx> >> >> diff -r 537451477469 xen/arch/x86/traps.c >> --- a/xen/arch/x86/traps.c Thu Apr 01 09:55:27 2010 +0100 >> +++ b/xen/arch/x86/traps.c Sat Apr 03 05:26:53 2010 +0800 >> @@ -776,7 +776,6 @@ static void pv_cpuid(struct cpu_user_reg >> __clear_bit(X86_FEATURE_PBE, &d); >> >> __clear_bit(X86_FEATURE_DTES64 % 32, &c); >> - __clear_bit(X86_FEATURE_MWAIT % 32, &c); >> __clear_bit(X86_FEATURE_DSCPL % 32, &c); >> __clear_bit(X86_FEATURE_VMXE % 32, &c); >> __clear_bit(X86_FEATURE_SMXE % 32, &c); >> @@ -814,7 +813,6 @@ static void pv_cpuid(struct cpu_user_reg >> __clear_bit(X86_FEATURE_SKINIT % 32, &c); >> __clear_bit(X86_FEATURE_WDT % 32, &c); >> break; >> - case 5: /* MONITOR/MWAIT */ >> case 0xa: /* Architectural Performance Monitor Features */ >> case 0x8000000a: /* SVM revision and features */ >> case 0x8000001b: /* Instruction Based Sampling */ > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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