linux-kernel - Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when L2 guest is running

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: <1a2c4809-ac93-d0cc-b79a-5ff891d7920c@redhat.com>
Date:	Wed, 6 Jul 2016 08:04:09 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Wanpeng Li <kernellwp@...il.com>,
	Haozhong Zhang <haozhong.zhang@...el.com>
Cc:	kvm <kvm@...r.kernel.org>, Radim Krcmar <rkrcmar@...hat.com>,
	Yunhong Jiang <yunhong.jiang@...el.com>,
	Wanpeng Li <wanpeng.li@...mail.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when
 L2 guest is running



On 06/07/2016 07:37, Wanpeng Li wrote:
> Cc Jan,
> 2016-07-06 13:10 GMT+08:00 Haozhong Zhang <haozhong.zhang@...el.com>:
>> A different VMCS is loaded when L2 guest is running, so it's incorrect
>> to use the VMX preemption timer for L1 TSC deadline timer. This patch
>> switches to hrtimer for L1 TSC deadline timer when entering L2 guest,
>> and switches back to VMX preemption timer when nested VMEXIT from L2 to
>> L1.
> 
> Nested preemption timer is emulated by hrtimer, so it doesn't
> influence vmcs02, why this is needed?

I agree (and nested APIC timer is emulated by L1).  Because the L1 APIC
timer is set in the preemption timer before vmentry, this should not be
necessary.

Paolo