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From: Alex Williamson <alex.williamson@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	peterx@redhat.com
Subject: Re: [PATCH 3/7] vfio/pci: Use vfio_device_unmap_mapping_range()
Date: Tue, 10 Aug 2021 15:50:58 -0600	[thread overview]
Message-ID: <20210810155058.4199a86b.alex.williamson@redhat.com> (raw)
In-Reply-To: <YRJ3JD7gyi11x5Hw@infradead.org>

On Tue, 10 Aug 2021 13:55:00 +0100
Christoph Hellwig <hch@infradead.org> wrote:

> 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.

Exactly.  Ideally we're not using that path often, but I don't think
that's a good excuse to introduce memory access serialization, or even
dependencies between devices.  Thanks,

Alex


  reply	other threads:[~2021-08-10 21:51 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05 17:06 [PATCH 0/7] vfio: device fd address space and vfio-pci mmap invalidation cleanup Alex Williamson
2021-08-05 17:07 ` [PATCH 1/7] vfio: Create vfio_fs_type with inode per device Alex Williamson
2021-08-10  8:43   ` Christoph Hellwig
2021-08-10 14:52     ` Alex Williamson
2021-08-10 14:57       ` Christoph Hellwig
2021-08-10 18:49         ` Peter Xu
2021-08-10 21:16           ` Alex Williamson
2021-08-10 22:18             ` Peter Xu
2021-08-05 17:07 ` [PATCH 2/7] vfio: Export unmap_mapping_range() wrapper Alex Williamson
2021-08-10  8:45   ` Christoph Hellwig
2021-08-10 18:56   ` Peter Xu
2021-08-05 17:07 ` [PATCH 3/7] vfio/pci: Use vfio_device_unmap_mapping_range() Alex Williamson
2021-08-06  1:04   ` Jason Gunthorpe
2021-08-06 20:17     ` Alex Williamson
2021-08-10  8:51       ` Christoph Hellwig
2021-08-10 11:57         ` Jason Gunthorpe
2021-08-10 12:55           ` Christoph Hellwig
2021-08-10 21:50             ` Alex Williamson [this message]
2021-08-11 11:57               ` Jason Gunthorpe
2021-08-10  8:53   ` Christoph Hellwig
2021-08-10 19:02     ` Peter Xu
2021-08-10 20:51       ` Alex Williamson
2021-08-10 18:48   ` Peter Xu
2021-08-10 19:59     ` Alex Williamson
2021-08-10 20:20       ` Peter Xu
2021-08-05 17:07 ` [PATCH 4/7] vfio,vfio-pci: Add vma to pfn callback Alex Williamson
2021-08-06  1:01   ` Jason Gunthorpe
2021-08-10  9:00     ` Christoph Hellwig
2021-08-10  9:00   ` Christoph Hellwig
2021-08-05 17:08 ` [PATCH 5/7] mm/interval_tree.c: Export vma interval tree iterators Alex Williamson
2021-08-05 17:08 ` [PATCH 6/7] vfio: Add vfio_device_io_remap_mapping_range() Alex Williamson
2021-08-10  9:04   ` Christoph Hellwig
2021-08-05 17:08 ` [PATCH 7/7] vfio/pci: Remove map-on-fault behavior Alex Williamson
2021-08-10  9:11   ` Christoph Hellwig
2021-08-10 15:04     ` Alex Williamson
2021-08-10 20:54   ` Peter Xu
2021-08-10 21:45     ` Alex Williamson
2021-08-10 22:27       ` Peter Xu

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