Re: [PATCH 1/4] x86: introduce hypervisor_cpuid_base()

Gleb Natapov
2013-07-23T13:48:55Z

On Tue, Jul 23, 2013 at 05:41:02PM +0800, Jason Wang wrote:
> This patch introduce hypervisor_cpuid_base() which loop test the hypervisor
> existence function until the signature match and check the number of leaves if
> required. This could be used by Xen/KVM guest to detect the existence of
> hypervisor.
>
Looks good to me.

Since this touches common code, kvm and xen I expect this to be taken
via the tip tree, correct?

> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: Gleb Natapov <gleb@redhat.com>
> Cc: x86@kernel.org
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> arch/x86/include/asm/processor.h | 20 ++++++++++++++++++++
> 1 files changed, 20 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 24cf5ae..a8136d0 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -971,6 +971,26 @@ unsigned long calc_aperfmperf_ratio(struct aperfmperf *old,
> return ratio;
> }
>
> +static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
> +{
> + uint32_t base, eax, ebx, ecx, edx;
> + char signature[13];
> +
> + for (base = 0x40000000; base < 0x40010000; base += 0x100) {
> + cpuid(base, &eax, &ebx, &ecx, &edx);
> + *(uint32_t *)(signature + 0) = ebx;
> + *(uint32_t *)(signature + 4) = ecx;
> + *(uint32_t *)(signature + 8) = edx;
> + signature[12] = 0;
> +
> + if (!strcmp(sig, signature) &&
> + (leaves == 0 || ((eax - base) >= leaves)))
> + return base;
> + }
> +
> + return 0;
> +}
> +
> extern unsigned long arch_align_stack(unsigned long sp);
> extern void free_init_pages(char *what, unsigned long begin, unsigned long end);
>
> --
> 1.7.1

--
Gleb.