Commit 9d532f28 authored Jul 27, 2020 by John Hubbard Committed by Alex Williamson Jul 27, 2020

vfio/spapr_tce: convert get_user_pages() --> pin_user_pages()

This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages*() + put_page() calls to
pin_user_pages*() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/



Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

parent e1907d67

drivers/vfio/vfio_iommu_spapr_tce.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -383,7 +383,7 @@ static void tce_iommu_unuse_page(struct tce_container *container,
		struct page *page;

		page = pfn_to_page(hpa >> PAGE_SHIFT);
		put_page(page);
		unpin_user_page(page);
		}

		static int tce_iommu_prereg_ua_to_hpa(struct tce_container *container,
		@@ -486,7 +486,7 @@ static int tce_iommu_use_page(unsigned long tce, unsigned long *hpa)
		struct page *page = NULL;
		enum dma_data_direction direction = iommu_tce_direction(tce);

		if (get_user_pages_fast(tce & PAGE_MASK, 1,
		if (pin_user_pages_fast(tce & PAGE_MASK, 1,
		direction != DMA_TO_DEVICE ? FOLL_WRITE : 0,
		&page) != 1)
		return -EFAULT;

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