From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Hogan <james.hogan@imgtec.com>
Subject: Re: [PATCH v2 11/23] MIPS: KVM: Fix timer race modifying guest CP0_Cause
Date: Thu, 29 May 2014 11:55:40 +0100
Message-ID: <5387122C.2080203@imgtec.com>
References: <1401355005-20370-1-git-send-email-james.hogan@imgtec.com> <1401355005-20370-12-git-send-email-james.hogan@imgtec.com> <53870D99.3030900@redhat.com>
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Cc: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>,
	Gleb Natapov <gleb@kernel.org>, <kvm@vger.kernel.org>,
	Ralf Baechle <ralf@linux-mips.org>,
	<linux-mips@linux-mips.org>, Sanjay Lal <sanjayl@kymasys.com>
To: Paolo Bonzini <pbonzini@redhat.com>
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Hi Paolo,

On 29/05/14 11:36, Paolo Bonzini wrote:
> Il 29/05/2014 11:16, James Hogan ha scritto:
>> Currently this is the only asynchronous modification of guest registers,
>> therefore it is fixed by adjusting the implementations of the
>> kvm_set_c0_guest_cause(), kvm_clear_c0_guest_cause(), and
>> kvm_change_c0_guest_cause() macros which are used for modifying the
>> guest CP0_Cause register to use ll/sc to ensure atomic modification.
> 
> Shouldn't you have a loop too around the ll/sc?

Yes, it has a do {} while () look around the inline asm, although I
didn't mention it in the commit message. It's modelled on
arch/mips/include/asm/bitops.h.

Cheers
James