linux-kernel - Re: [PATCH 3.12 81/88] KVM: x86: expose invariant tsc cpuid bit (v2)

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Date:	Thu, 14 Jul 2016 10:40:00 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Jiri Slaby <jslaby@...e.cz>, stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH 3.12 81/88] KVM: x86: expose invariant tsc cpuid bit (v2)



On 14/07/2016 10:16, Jiri Slaby wrote:
> From: Marcelo Tosatti <mtosatti@...hat.com>
> 
> 3.12-stable review patch.  If anyone has any objections, please let me know.

Why stable?  The commit is in 3.16, but AFAICS it never went into other
stable kernels.

Paolo

> ===============
> 
> commit e4c9a5a17567f8ea975bdcfdd1bf9d63965de6c9 upstream.
> 
> Invariant TSC is a property of TSC, no additional
> support code necessary.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> ---
>  arch/x86/kvm/cpuid.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index b132551528e5..6620ac307215 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -437,6 +437,13 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  		entry->ecx &= kvm_supported_word6_x86_features;
>  		cpuid_mask(&entry->ecx, 6);
>  		break;
> +	case 0x80000007: /* Advanced power management */
> +		/* invariant TSC is CPUID.80000007H:EDX[8] */
> +		entry->edx &= (1 << 8);
> +		/* mask against host */
> +		entry->edx &= boot_cpu_data.x86_power;
> +		entry->eax = entry->ebx = entry->ecx = 0;
> +		break;
>  	case 0x80000008: {
>  		unsigned g_phys_as = (entry->eax >> 16) & 0xff;
>  		unsigned virt_as = max((entry->eax >> 8) & 0xff, 48U);
> @@ -467,7 +474,6 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  	case 3: /* Processor serial number */
>  	case 5: /* MONITOR/MWAIT */
>  	case 6: /* Thermal management */
> -	case 0x80000007: /* Advanced power management */
>  	case 0xC0000002:
>  	case 0xC0000003:
>  	case 0xC0000004:
>