linux-kernel - Re: [PATCH 08/12] KVM: x86: Use the correct vcpu's TSC rate to compute time scale

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20151005201233.GA31314@potion.brq.redhat.com>
Date:	Mon, 5 Oct 2015 22:12:34 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Haozhong Zhang <haozhong.zhang@...el.com>
Cc:	kvm@...r.kernel.org, Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Joerg Roedel <joro@...tes.org>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	Mihai Donțu <mdontu@...defender.com>,
	Andy Lutomirski <luto@...nel.org>,
	Kai Huang <kai.huang@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] KVM: x86: Use the correct vcpu's TSC rate to
 compute time scale

2015-09-28 13:38+0800, Haozhong Zhang:
> This patch makes KVM use virtual_tsc_khz rather than the host TSC rate
> as vcpu's TSC rate to compute the time scale if TSC scaling is enabled.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@...el.com>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> @@ -1782,7 +1782,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
>  		return 0;
>  
>  	if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
> -		kvm_get_time_scale(NSEC_PER_SEC / 1000, this_tsc_khz,
> +		tgt_tsc_khz = kvm_has_tsc_control ?
> +			vcpu->virtual_tsc_khz : this_tsc_khz;
> +		kvm_get_time_scale(NSEC_PER_SEC / 1000, tgt_tsc_khz,
>  				   &vcpu->hv_clock.tsc_shift,
>  				   &vcpu->hv_clock.tsc_to_system_mul);

Good catch, it seems that SVM didn't scale kvmclock correctly ...
I think we'll want this patch in stable.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/