Re: [PATCH] kvm: pass the virtual SEI syndrome to guest OS

From: Christoffer Dall <cdall@linaro.org>
To: James Morse <james.morse@arm.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	gengdongjiu <gengdongjiu@huawei.com>,
	wangxiongfeng2@huawei.com, wuquanming@huawei.com,
	huangshaoyu@huawei.com,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Andre Przywara <andre.przywara@arm.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>
Subject: Re: [PATCH] kvm: pass the virtual SEI syndrome to guest OS
Date: Tue, 21 Mar 2017 20:36:19 +0100	[thread overview]
Message-ID: <CAMJs5B-UVU0VfY2dTidLw_f5Gr5qsDfgdTkf7HGdoPXOJoa26w@mail.gmail.com> (raw)
In-Reply-To: <58D17AF0.2010802@arm.com>

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On Tue, Mar 21, 2017 at 8:11 PM, James Morse <james.morse@arm.com> wrote:

> Hi Christoffer,
>
> On 21/03/17 11:34, Christoffer Dall wrote:
> > On Tue, Mar 21, 2017 at 02:32:29PM +0800, gengdongjiu wrote:
> >> On 2017/3/20 23:08, James Morse wrote:
> >>>>>> On 20/03/17 07:55, Dongjiu Geng wrote:
> >>>>>>> In the RAS implementation, hardware pass the virtual SEI
> >>>>>>> syndrome information through the VSESR_EL2, so set the virtual
> >>>>>>> SEI syndrome using physical SEI syndrome el2_elr to pass to
> >>>>>>> the guest OS
> >>>
> >>> How does this work with firmware first?
> >>
> >> I explained it in previous mail about the work flow.
> >
> > When delivering and reporting SEIs to the VM, should this happen
> > directly to the OS running in the VM, or to the guest firmware (e.g.
> > UEFI) running in the VM as well?
>
> 'firmware first' is the ACPI specs name for x86's BIOS or management-mode
> handling the error. On arm64 we have multiple things called firmware, so
> the
> name might be more confusing than helpful.
>
> As far as I understand it, firmware here refers to the secure-world and
> EL3.
> Something like ATF can use SCR_EL3.EA to claim SErrors and external aborts,
> routing them to EL3 where secure platform specific firmware generates CPER
> records.
> For a guest, Qemu takes the role of this EL3-firmware.
>
>
Thanks for the clarification.  So UEFI in the VM would not be involved in
this at all?

My confusion here comes from not thinking about QEMU or KVM as firmware,
but as the machine, so it would be sort of like the functionality is baked
into hardware rather than firmware.

Note that to the VM, the environment will look like hardware without EL3
and without a secure world, so any software assuming there's something
'hidden' behind the available non-secure modes must not decide to disable
features if discovering the lack of a secure world.

Thanks,
-Christoffer

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