On Mon, Dec 8, 2014 at 7:45 AM, Konrad Rzeszutek Wilk
<[email protected]> wrote:
> On Fri, Dec 05, 2014 at 07:03:28PM -0800, Andy Lutomirski wrote:
>> paravirt_enabled has the following effects:
>>
>> - Disables the F00F bug workaround warning. There is no F00F bug
>> workaround any more because Linux's standard IDT handling already
>> works around the F00F bug, but the warning still exists. This
>> is only cosmetic, and, in any event, there is no such thing as
>> KVM on a CPU with the F00F bug.
>>
>> - Disables 32-bit APM BIOS detection. On a KVM paravirt system,
>> there should be no APM BIOS anyway.
>>
>> - Disables tboot. I think that the tboot code should check the
>> CPUID hypervisor bit directly if it matters.
>>
>> - paravirt_enabled disables espfix32. espfix32 should *not* be
>> disabled under KVM paravirt.
>>
>> The last point is the purpose of this patch. It fixes a leak of the
>> high 16 bits of the kernel stack address on 32-bit KVM paravirt
>> guests.
>>
>> While I'm at it, this removes pv_info setup from kvmclock. That
>> code seems to serve no purpose.
>>
>> Cc: [email protected]
>> Signed-off-by: Andy Lutomirski <[email protected]>
>
> Suggested-by: Konrad Rzeszutek Wilk <[email protected]>
Sorry, meant to add that but forgot. Too many patches late last week :(
>> ---
>> arch/x86/kernel/kvm.c | 9 ++++++++-
>> arch/x86/kernel/kvmclock.c | 2 --
>> 2 files changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index f6945bef2cd1..94f643484300 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -283,7 +283,14 @@ NOKPROBE_SYMBOL(do_async_page_fault);
>> static void __init paravirt_ops_setup(void)
>> {
>> pv_info.name = "KVM";
>> - pv_info.paravirt_enabled = 1;
>> +
>> + /*
>> + * KVM isn't paravirt in the sense of paravirt_enabled. A KVM
>> + * guest kernel works like a bare metal kernel with additional
>> + * features, and paravirt_enabled is about features that are
>> + * missing.
>> + */
>> + pv_info.paravirt_enabled = 0;
>>
>> if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
>> pv_cpu_ops.io_delay = kvm_io_delay;
>> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
>> index d9156ceecdff..d4d9a8ad7893 100644
>> --- a/arch/x86/kernel/kvmclock.c
>> +++ b/arch/x86/kernel/kvmclock.c
>> @@ -263,8 +263,6 @@ void __init kvmclock_init(void)
>> #endif
>> kvm_get_preset_lpj();
>> clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
>> - pv_info.paravirt_enabled = 1;
>> - pv_info.name = "KVM";
>>
>> if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
>> pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
>> --
>> 1.9.3
>>
--
Andy Lutomirski
AMA Capital Management, LLC
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