Subject: Re: [PATCH V11 10/10] arm/arm64: KVM: add guest SEA support
To: Xiongfeng Wang <wangxiongfeng2@huawei.com>,
        James Morse <james.morse@arm.com>
References: <1487712121-16688-1-git-send-email-tbaicar@codeaurora.org>
 <1487712121-16688-11-git-send-email-tbaicar@codeaurora.org>
 <df6ba5dc-d93f-925a-46bf-1e1e209d17f3@huawei.com> <58B43092.6040401@arm.com>
 <3df82a7b-1a32-e2d7-ae78-7132a4eab1a0@huawei.com> <58B57941.3000703@arm.com>
 <4ff98823-d6f0-eb2e-4b98-f6d5e255f6c3@huawei.com>
Cc: punit.agrawal@arm.com, mark.rutland@arm.com, linux-efi@vger.kernel.org,
        kvm@vger.kernel.org, rkrcmar@redhat.com, matt@codeblueprint.co.uk,
        catalin.marinas@arm.com, Tyler Baicar <tbaicar@codeaurora.org>,
        will.deacon@arm.com, linux@armlinux.org.uk,
        paul.gortmaker@windriver.com, lv.zheng@intel.com,
        kvmarm@lists.cs.columbia.edu, fu.wei@linaro.org, tn@semihalf.com,
        zjzhang@codeaurora.org, robert.moore@intel.com,
        linux-acpi@vger.kernel.org, eun.taik.lee@samsung.com,
        shijie.huang@arm.com, labbott@redhat.com, lenb@kernel.org,
        harba@codeaurora.org, Suzuki.Poulose@arm.com, john.garry@huawei.com,
        rostedt@goodmis.org, nkaje@codeaurora.org, sandeepa.s.prabhu@gmail.com,
        linux-arm-kernel@lists.infradead.org, devel@acpica.org,
        rjw@rjwysocki.net, rruigrok@codeaurora.org,
        linux-kernel@vger.kernel.org, astone@redhat.com, hanjun.guo@linaro.org,
        joe@perches.com, pbonzini@redhat.com, akpm@linux-foundation.org,
        bristot@redhat.com, christoffer.dall@linaro.org, shiju.jose@huawei.com
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
Message-ID: <6d0fa5a5-bcbf-38b8-45ac-d645220ee9e2@arm.com>
Date: Thu, 2 Mar 2017 09:39:21 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Icedove/45.6.0
MIME-Version: 1.0
In-Reply-To: <4ff98823-d6f0-eb2e-4b98-f6d5e255f6c3@huawei.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1661
Lines: 36

On 01/03/17 02:31, Xiongfeng Wang wrote:

[lot of things]

> If an SEA is injected into guest OS, the guest OS will jump to the SEA
> exception entry when the context switched to guest OS. And the CPSR and
> FAR_EL1 are recovered according to the content of vcpu. Then the guest
> OS can signal a process or panic. If another guest process read the
> error data, another SEA will be generated and it will be single too.
> 
> Without QEMU involved, the drawback is that no APEI table can be mocked
> up in guest OS, and no memory_failure() will be called. So the memory of
> error data will be released into buddy system and assigned to another
> process. If the error was caused by instantaneous radiation or
> electromagnetic, the memory is usable again if it is written with a
> correct data. If the memory has wore out and a correct data is written,
> the ECC error may occurs again with high possibility. Before a 2-bit ECC
> error is reported, much more 1-bit errors will be reported. This is
> report to host os, the host os can determine the memory node has worn
> out and hot-plug out the memory node, and guest os may be terminated if
> its memory data can't be migrated.
> 
> Of course, it is better to get QEMU involved, so the memory_failure can
> be executed in guest OS. But before that implemented, can we add SEA
> injection in kvm_handle_guest_abort()?

No. I will strongly object to that. This is a platform decision to
forward SEAs, not an architectural one. The core KVM code is only
concerned about implementing the ARM architecture, and not something
that is firmware dependent.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...