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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 7/7] vfio/pci: Remove map-on-fault behavior
Date: Tue, 10 Aug 2021 09:04:02 -0600	[thread overview]
Message-ID: <20210810090402.0a120276.alex.williamson@redhat.com> (raw)
In-Reply-To: <YRJC1buKp67kGemh@infradead.org>

On Tue, 10 Aug 2021 11:11:49 +0200
Christoph Hellwig <hch@infradead.org> wrote:

> On Thu, Aug 05, 2021 at 11:08:21AM -0600, Alex Williamson wrote:
> > +void vfio_pci_test_and_up_write_memory_lock(struct vfio_pci_device *vdev)
> > +{
> > +	if (vdev->zapped_bars && __vfio_pci_memory_enabled(vdev)) {
> > +		WARN_ON(vfio_device_io_remap_mapping_range(&vdev->vdev,
> > +			VFIO_PCI_INDEX_TO_OFFSET(VFIO_PCI_BAR0_REGION_INDEX),
> > +			VFIO_PCI_INDEX_TO_OFFSET(VFIO_PCI_ROM_REGION_INDEX) -
> > +			VFIO_PCI_INDEX_TO_OFFSET(VFIO_PCI_BAR0_REGION_INDEX)));
> > +		vdev->zapped_bars = false;  
> 
> Doing actual work inside a WARN_ON is pretty nasty.  Also the non-ONCE
> version here will lead to massive log splatter if it actually hits.
> 
> I'd prefer something like:
> 
> 	loff_t start = VFIO_PCI_INDEX_TO_OFFSET(VFIO_PCI_BAR0_REGION_INDEX);
> 	loff_t end = VFIO_PCI_INDEX_TO_OFFSET(VFIO_PCI_ROM_REGION_INDEX);
> 
> 	if (vdev->zapped_bars && __vfio_pci_memory_enabled(vdev)) {
> 		if (!vfio_device_io_remap_mapping_range(&vdev->vdev, start,
> 				end - start))
> 			vdev->zapped_bars = false;
> 		WARN_ON_ONCE(vdev->zapped_bars);
> 
> >  	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> > -	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);  
> 
> What is the story with this appearing earlier and disappearing here
> again?

We switched from io_remap_pfn_range() which includes this flag
implicitly, to vmf_insert_pfn() which does not, and back to
io_remap_pfn_range() when the fault handler is removed.

> > +extern void vfio_pci_test_and_up_write_memory_lock(struct vfio_pci_device
> > +						   *vdev);  
> 
> No need for the extern.

Thanks much for the reviews!

Alex


  reply	other threads:[~2021-08-10 15:04 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
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 [this message]
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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