linux-kernel - Re: [PATCH v6 5/7] arm64: kvm: route synchronous external abort exceptions to el2

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Date:   Thu, 14 Sep 2017 19:12:06 +0800
From:   gengdongjiu <gengdongjiu@...wei.com>
To:     James Morse <james.morse@....com>
CC:     <christoffer.dall@...aro.org>, <marc.zyngier@....com>,
        <rkrcmar@...hat.com>, <linux@...linux.org.uk>,
        <catalin.marinas@....com>, <will.deacon@....com>,
        <lenb@...nel.org>, <robert.moore@...el.com>, <lv.zheng@...el.com>,
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        <cov@...eaurora.org>, <david.daney@...ium.com>,
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        <wangkefeng.wang@...wei.com>, <tbaicar@...eaurora.org>,
        <ard.biesheuvel@...aro.org>, <mingo@...nel.org>, <bp@...e.de>,
        <shiju.jose@...wei.com>, <zjzhang@...eaurora.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
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Subject: Re: [PATCH v6 5/7] arm64: kvm: route synchronous external abort
 exceptions to el2

James,

On 2017/9/8 0:31, James Morse wrote:
> KVM already handles external aborts from lower exception levels, no more work
> needs doing for TEA.
If it is firmware first solution, that is SCR_EL3.EA=1, all SError interrupt and synchronous External
Abort exceptions are taken to EL3, so EL3 firmware will handle it, KVM no needs to handle it.

HCR_EL3.TEA is only for EL3 to check its value to decide to jump to hypervisor or kernel.

> 
> What happens when a guest access the RAS-Error-Record registers?
> 
> Before we can set HCR_EL2.TERR I think we need to add some minimal emulation for
> the registers it traps. Most of them should be RAZ/WI, so it should be
> straightforward. (I think KVMs default is to emulate an undef for unknown traps).
Today I added the support to do some minimal emulation for RAS-Error-Record registers, thanks
for the good suggestion.

> 
> Eventually we will want to back this with a page of memory that lets
> Qemu/kvmtool configure what the guest can see. (i.e. the emulated machine's
> errors for kernel-first handling.)