linux-kernel - Re: [PATCH v2 0/5] KVM: x86: improve reexecute

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Date:	Tue, 11 Dec 2012 21:36:41 -0200
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Gleb Natapov <gleb@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 0/5] KVM: x86: improve reexecute_instruction

On Mon, Dec 10, 2012 at 05:11:35PM +0800, Xiao Guangrong wrote:
> Changelog:
> There are some changes from Marcelo and Gleb's review, thank you all!
> - access indirect_shadow_pages in the protection of mmu-lock
> - fix the issue when unhandleable instruction access on large page
> - add a new test case for large page
> 
> The current reexecute_instruction can not well detect the failed instruction
> emulation. It allows guest to retry all the instructions except it accesses
> on error pfn.
> 
> For example, these cases can not be detected:
> - for tdp used
>   currently, it refused to retry all instructions. If nested npt is used, the
>   emulation may be caused by shadow page, it can be fixed by unshadow the
>   shadow page.
> 
> - for shadow mmu
>   some cases are nested-write-protect, for example, if the page we want to
>   write is used as PDE but it chains to itself. Under this case, we should
>   stop the emulation and report the case to userspace.
> 
> There are two test cases based on kvm-unit-test can trigger a infinite loop on
> current code (ept = 0), after this patchset, it can report the error to Qemu.
> 
> Subject: [PATCH] access test: test unhandleable instruction
> 
> Test the instruction which can not be handled by kvm
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>

Please submit the test for inclusion. There should be some way to make
it fail.. program a timer interrupt and #GP? 

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