linux-kernel - Re: [PATCH] KVM: x86: Kick VCPU outside PIC lock again

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]

Date:	Wed, 24 Feb 2010 12:41:42 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>
CC:	Thomas Gleixner <tglx@...utronix.de>, KVM <kvm@...r.kernel.org>,
	Gleb Natapov <gleb@...hat.com>,
	RT <linux-rt-users@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: Kick VCPU outside PIC lock again

On 02/24/2010 12:28 PM, Jan Kiszka wrote:
> Jan Kiszka wrote:
>    
>> Avi Kivity wrote:
>>      
>>> On 02/24/2010 12:13 PM, Jan Kiszka wrote:
>>>        
>>>>
>>>>          
>>>>> I see.  Won't we hit the same issue when we call pic functions from
>>>>> atomic context during the guest entry sequence?
>>>>>
>>>>>
>>>>>            
>>>> If there are such call paths, for sure. What concrete path(s) do you
>>>> have in mind?
>>>>
>>>>
>>>>          
>>> vcpu_enter_guest() ->  inject_pending_event() ->
>>> kvm_cpu_{has,get}_interrupt() ->  various pic functions if you're unlucky.
>>>        
>> But do they kick anyone or just check/pull information? Never saw any
>> warnings during my tests last year (granted: with older -rt and kvm
>> versions).
>>      
> Mmh, they could if there is>  1 IRQ pending. Guess this just never
> triggered in real life due to typical APIC use and low IRQ load during
> PIC times in my tests.
>    

We could just ignore the wakeup in this path.  It's called in vcpu 
context, so obviously the vcpu is awake and kicking it will only hurt 
your feet.

Longer term, we should clear up this mess.  One possible path is to move 
the pic/lapic/injection stuff out of the the critical section, and use 
vcpu->requests to close the race between querying the pic/lapic and 
entering the guest.

-- 
error compiling committee.c: too many arguments to function

--
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/