linux-kernel - Re: [PATCH 3/7] vfio/pci: Use vfio_device_unmap_mapping

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Message-ID: <YRJ3JD7gyi11x5Hw@infradead.org>
Date:   Tue, 10 Aug 2021 13:55:00 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        peterx@...hat.com
Subject: Re: [PATCH 3/7] vfio/pci: Use vfio_device_unmap_mapping_range()

On Tue, Aug 10, 2021 at 08:57:22AM -0300, Jason Gunthorpe wrote:
> I'm not sure there is a real performance win to chase here? Doesn't
> this only protect mmap against reset? The mmap isn't performance
> sensitive, right?
> 
> If this really needs extra optimization adding a rwsem to the devset
> and using that across the whole set would surely be sufficient.

Every mmio read or write takes memory_lock.