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

[Marc Zyngier <maz@kernel.org>]

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.
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...