linux-kernel - Re: [RFC PATCH v2 7/7] KVM: KVM: don't break vcpu 'halt' state due to apfs

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: <4CCFD556.3070504@cn.fujitsu.com>
Date:	Tue, 02 Nov 2010 17:09:42 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [RFC PATCH v2 7/7] KVM: KVM: don't break vcpu 'halt' state due
 to apfs

On 11/02/2010 03:45 PM, Gleb Natapov wrote:

> kvm_event_needs_reinjection() checks for nmi/interrupts that
> need reinjection (not injection).  Those are nmi/interrupts that
> was injected but injection failed for some reason. For nmi, for
> instance, kvm_arch_vcpu_runnable() checks vcpu->arch.nmi_pending,
> but kvm_event_needs_reinjection() checks for vcpu->arch.nmi_injected.
> NMI moves from nmi_pending to nmi_injected when it is injected into vcpu
> for the first time. CPU cannot be halted in this state.
> 

Yeah, nmi is handled like this way, but for interrupt:
If interruption controller is in userspace (!irqchip_in_kernel(v->kvm)),
kvm_arch_vcpu_runnable() checks vcpu->arch.interrupt.pending and
kvm_event_needs_reinjection() also checks vcpu->arch.interrupt.pending.

Consider this case:

- Guest vcpu executes 'HLT'
- wakeup the vcpu and inject interrupt and apfs is completed at this time
- then the vcpu can't handle apf completion and .done list keeps nonempty.  

Can this case happen? Sorry if i missed it again.

>> Also, the pv guest can only handle an apf completion at one time, it can not ensure
>> vcpu->async_pf.done is empty after kvm_check_async_pf_completion()
>>
> In case of PV guest it will be woken up by apf completion by
> kvm_arch_async_page_present() below.

......

>> As i know, exception can not let guest exit halt state, only NMI/interruption can do it, yes? :-)
> On physical HW exception cannot happen while cpu is in halt state, but
> with PV we define what guest can and cannot expect, so when guest
> explicitly enables apf it should be able to handle it during halt.
> 

Ah, i see, thanks your very much.
--
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/