linux-kernel - Re: [PATCH v6 11/12] Let host know whether the guest can handle async PF in non-userspace context.

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Message-ID: <4CADCCF8.5000408@redhat.com>
Date:	Thu, 07 Oct 2010 15:36:56 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	kvm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, hpa@...or.com,
	riel@...hat.com, cl@...ux-foundation.org, mtosatti@...hat.com
Subject: Re: [PATCH v6 11/12] Let host know whether the guest can handle async
 PF in non-userspace context.

  On 10/04/2010 05:56 PM, Gleb Natapov wrote:
> If guest can detect that it runs in non-preemptable context it can
> handle async PFs at any time, so let host know that it can send async
> PF even if guest cpu is not in userspace.
>
>
>
>   MSR_KVM_ASYNC_PF_EN: 0x4b564d02
>   	data: Bits 63-6 hold 64-byte aligned physical address of a 32bit memory
> -	area which must be in guest RAM. Bits 5-1 are reserved and should be
> +	area which must be in guest RAM. Bits 5-2 are reserved and should be
>   	zero. Bit 0 is 1 when asynchronous page faults are enabled on the vcpu
> -	0 when disabled.
> +	0 when disabled. Bit 2 is 1 if asynchronous page faults can be injected
> +	when vcpu is in kernel mode.

Please use cpl instead of user mode and kernel mode.  The original terms 
are ambiguous for cpl ==1 || cpl == 2.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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