linux-kernel - Re: [PATCH 3/3] vfio-pci: Invalidate mmaps and block MMIO access on disabled memory

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Message-ID: <20200505183629.GF26002@ziepe.ca>
Date:   Tue, 5 May 2020 15:36:29 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        cohuck@...hat.com, peterx@...hat.com
Subject: Re: [PATCH 3/3] vfio-pci: Invalidate mmaps and block MMIO access on
 disabled memory

On Tue, May 05, 2020 at 11:12:27AM -0600, Alex Williamson wrote:
> 
> As noted in the comment, the fault handler can simply do:
> 
> mutex_lock(&vdev->vma_lock);
> down_read(&vdev->memory_lock);
> 
> This should be deadlock free now, so we can drop the retry handling

That does look like the right direction, because the memory_lock can
be done at the very end it means it doesn't need to be nested inside
mmap_sem

This is much cleaner!

Jason