linux-kernel - Re: [PATCH V3 10/10] arm64: KVM: add guest SEA support

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Date:   Fri, 14 Oct 2016 14:58:18 -0700
From:   "Baicar, Tyler" <tbaicar@...eaurora.org>
To:     Punit Agrawal <punit.agrawal@....com>
Cc:     linux-efi@...r.kernel.org, matt@...eblueprint.co.uk,
        catalin.marinas@....com, will.deacon@....com,
        robert.moore@...el.com, paul.gortmaker@...driver.com,
        lv.zheng@...el.com, kvmarm@...ts.cs.columbia.edu,
        fu.wei@...aro.org, linux@...linux.org.uk,
        linux-acpi@...r.kernel.org, shijie.huang@....com, lenb@...nel.org,
        marc.zyngier@....com, tomasz.nowicki@...aro.org,
        rostedt@...dmis.org, sandeepa.s.prabhu@...il.com,
        Dkvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devel@...ica.org, rjw@...ysocki.net, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, akpm@...ux-foundation.org, bristot@...hat.com
Subject: Re: [PATCH V3 10/10] arm64: KVM: add guest SEA support

On 10/14/2016 2:38 AM, Punit Agrawal wrote:
> "Baicar, Tyler" <tbaicar@...eaurora.org> writes:
>
>> Hello Punit,
>>
>> On 10/13/2016 7:14 AM, Punit Agrawal wrote:
>>> Hi Tyler,
>>>
>>> I know I've had my last comment already ;), but I thought I'd rather
>>> raise the question than stay confused...
>>>
>>> Tyler Baicar <tbaicar@...eaurora.org> writes:
>>>
>>>> Currently external aborts are unsupported by the guest abort
>>>> handling. Add handling for SEAs so that the host kernel reports
>>>> SEAs which occur in the guest kernel.
>>>>
>>>> Signed-off-by: Tyler Baicar <tbaicar@...eaurora.org>
>>>> ---
>>>>    arch/arm/include/asm/kvm_arm.h       |  1 +
>>>>    arch/arm/include/asm/system_misc.h   |  5 +++++
>>>>    arch/arm/kvm/mmu.c                   | 15 +++++++++++++--
>>>>    arch/arm64/include/asm/kvm_arm.h     |  1 +
>>>>    arch/arm64/include/asm/system_misc.h |  2 ++
>>>>    arch/arm64/mm/fault.c                | 13 +++++++++++++
>>>>    6 files changed, 35 insertions(+), 2 deletions(-)
[...]
>>>> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
>>>> index 81cb7ad..d714432 100644
>>>> --- a/arch/arm64/mm/fault.c
>>>> +++ b/arch/arm64/mm/fault.c
>>>> @@ -597,6 +597,19 @@ static const char *fault_name(unsigned int esr)
>>>>    }
>>>>      /*
>>>> + * Handle Synchronous External Aborts that occur in a guest kernel.
>>>> + */
>>>> +int handle_guest_sea(unsigned long addr, unsigned int esr)
>>>> +{
>>>> +	atomic_notifier_call_chain(&sea_handler_chain, 0, NULL);
>>>> +
>>>> +	pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
>>>> +		fault_name(esr), esr, addr);
>>>> +
>>>> +	return 0;
>>>> +}
>>> Don't we need to pass the abort to the guest?
>> This requires some infrastructure to implement virtual "ACPI platform
>> error interface" to expose the details of the abort to the guest. This
>> patchset does not cover that and focuses on feature parity with other
>> architectures that support APEI. There are discussions among Linaro
>> partners about how this can be achieved in the long term, but that
>> work is outside the scope of this patchset. This patch will ensure
>> that if a guest encounters one of these errors then it will be
>> reported before getting killed. Before this patch we would just get an
>> unsupported FSC print out and then the guest would be killed.
> OK.
>
> I think we might be talking about different things though.
>
> I am referring to the injection of the synchronous external abort into
> the guest - similar to what's been done for prefetch abort in the
> kvm_guest_handle_abort.
>
> Maybe there is no benefit in passing the abort to the guest. In that
> case, can you please add a comment where you handle external abort
> (FSC_EXTABT) in kvm_guest_handle_abort.
Yes, I will add a comment there in the next version.

Thanks,
Tyler

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