Re: [PATCH stable-5.7] KVM: arm64: Synchronize sysreg state on injecting an AArch32 exception

[Marc Zyngier <maz@kernel.org>]

On 2020-06-16 14:19, Marc Zyngier wrote:
> Hi Greg,
> 
> On 2020-06-16 14:09, Greg KH wrote:
>> On Tue, Jun 16, 2020 at 01:52:00PM +0100, Marc Zyngier wrote:
>>> commit 0370964dd3ff7d3d406f292cb443a927952cbd05 upstream
>>> 
>>> On a VHE system, the EL1 state is left in the CPU most of the time,
>>> and only syncronized back to memory when vcpu_put() is called (most
>>> of the time on preemption).
>>> 
>>> Which means that when injecting an exception, we'd better have a way
>>> to either:
>>> (1) write directly to the EL1 sysregs
>>> (2) synchronize the state back to memory, and do the changes there
>>> 
>>> For an AArch64, we already do (1), so we are safe. Unfortunately,
>>> doing the same thing for AArch32 would be pretty invasive. Instead,
>>> we can easily implement (2) by calling the put/load architectural
>>> backends, and keep preemption disabled. We can then reload the
>>> state back into EL1.
>>> 
>>> Cc: stable@vger.kernel.org
>>> Reported-by: James Morse <james.morse@arm.com>
>>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>>> ---
>>>  virt/kvm/arm/aarch32.c | 28 ++++++++++++++++++++++++++++
>>>  1 file changed, 28 insertions(+)
>> 
>> Thanks for this, and the other backport.  Queued up.
> 
> You seem to have queued the same patches for 5.4 and 5.6.

Huh, and 4.19 as well. Gahh...

> This will break 32bit ARM (the patch applies nicely, but it will blow
> up at compile time).
> 
> I'll have the corresponding backports later today, once I've finished
> testing them.
> 
> Thanks,
> 
>         M.

-- 
Jazz is not dead. It just smells funny...