linux-kernel - Re: [PATCH V11 10/10] arm/arm64: KVM: add guest SEA support

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Message-ID: <6d0fa5a5-bcbf-38b8-45ac-d645220ee9e2@arm.com>
Date:   Thu, 2 Mar 2017 09:39:21 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        James Morse <james.morse@....com>
Cc:     punit.agrawal@....com, mark.rutland@....com,
        linux-efi@...r.kernel.org, kvm@...r.kernel.org, rkrcmar@...hat.com,
        matt@...eblueprint.co.uk, catalin.marinas@....com,
        Tyler Baicar <tbaicar@...eaurora.org>, will.deacon@....com,
        linux@...linux.org.uk, paul.gortmaker@...driver.com,
        lv.zheng@...el.com, kvmarm@...ts.cs.columbia.edu,
        fu.wei@...aro.org, tn@...ihalf.com, zjzhang@...eaurora.org,
        robert.moore@...el.com, linux-acpi@...r.kernel.org,
        eun.taik.lee@...sung.com, shijie.huang@....com, labbott@...hat.com,
        lenb@...nel.org, harba@...eaurora.org, Suzuki.Poulose@....com,
        john.garry@...wei.com, rostedt@...dmis.org, nkaje@...eaurora.org,
        sandeepa.s.prabhu@...il.com, linux-arm-kernel@...ts.infradead.org,
        devel@...ica.org, rjw@...ysocki.net, rruigrok@...eaurora.org,
        linux-kernel@...r.kernel.org, astone@...hat.com,
        hanjun.guo@...aro.org, joe@...ches.com, pbonzini@...hat.com,
        akpm@...ux-foundation.org, bristot@...hat.com,
        christoffer.dall@...aro.org, shiju.jose@...wei.com
Subject: Re: [PATCH V11 10/10] arm/arm64: KVM: add guest SEA support

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...