Re: [PATCH 0/2] KVM: arm: fix KVM_CAP_ARM_INJECT_EXT_DABT for aarch32 guests

From: Beata Michalska <beata.michalska@linaro.org>
To: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>, kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 0/2] KVM: arm: fix KVM_CAP_ARM_INJECT_EXT_DABT for aarch32 guests
Date: Fri, 24 Jan 2020 15:39:29 +0000	[thread overview]
Message-ID: <CADSWDzubQHvG8_c6a7E=basbtXxW-7u_ZVRz6+M7zGOAYYxz7A@mail.gmail.com> (raw)
In-Reply-To: <20200121123356.203000-1-james.morse@arm.com>

Hi James,

Thanks for the fixes - they work like a charm.

On Tue, 21 Jan 2020 at 12:34, James Morse <james.morse@arm.com> wrote:
>
> Beata reports that KVM_CAP_ARM_INJECT_EXT_DABT doesn't do the expected
> thing for aarch32 guests. We get the wrong register layout, and weren't
> even trying to set a 'external abort' in the first place!
>
> Both patches are intended as fixes, but patch 2 is somewhat in the eye
> of the beholder. I don't know why an imp-def exception was picked...
>
On a side note - currently KVM exposes capability that is not fully supported
(till the fix gets applied) and there is no easy way for the user space to
determine whether the injection will work as expected and whether it is safe to
use it or not. Although this is addressing a problem that is not that common
(I suppose) but still it might be worth to add a way for the kernel to inform
the user-space that it is all good to go? There has been a 'similar' case in the
past with KVM_SET_USER_MEMORY_REGION, where fixes where needed
and those were announced through new caps. Now, I'm not sure if adding new
capability would be the best approach here though it seems that there is not
much of a choice?

Best Regards
Beata

> Thanks,
>
> James Morse (2):
>   KVM: arm: fix DFSR setting for non-LPAE aarch32 guests
>   KVM: arm: Make inject_abt32() inject an external abort instead
>
>  virt/kvm/arm/aarch32.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
>
> --
> 2.24.1
>
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