Re: [PATCH 3/4] vpci: shrink critical section in vpci_{read/write}

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Feb 01, 2022 at 06:25:07PM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> 
> Shrink critical section in vpci_{read/write} as racing calls to
> vpci_{read,write}_hw() shouldn't be a problem. Those are just wrappers
> around pci_conf_{read,write} functions, and the required locking (in
> case of using the IO ports) is already taken care in pci_conf_{read,write}.
> 
> Please note, that we anyways split 64bit writes into two 32bit ones
> without taking the lock for the whole duration of the access, so it is
> possible to see a partially updated state as a result of a 64bit write:
> the PCI(e) specification don't seem to specify whether the ECAM is allowed
> to split memory transactions into multiple Configuration Requests and
> whether those could then interleave with requests from a different CPU.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Would like to make sure whether Jan still have concerns about
splitting accesses though. Also since I'm the maintainer we need a
Reviewed-by from someone else.

Thanks, Roger.