From: John Hubbard <jhubbard@nvidia.com>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>,
John Hubbard <jhubbard@nvidia.com>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>, <kvm@vger.kernel.org>
Subject: [PATCH 1/1] vfio/spapr_tce: convert get_user_pages() --> pin_user_pages()
Date: Fri, 22 May 2020 18:43:47 -0700 [thread overview]
Message-ID: <20200523014347.193290-1-jhubbard@nvidia.com> (raw)
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>
---
Hi,
I'm compile-tested this, but am not able to run-time test, so any
testing help is much appreciated!
thanks,
John Hubbard
NVIDIA
drivers/vfio/vfio_iommu_spapr_tce.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 16b3adc508db..fe888b5dcc00 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -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;
--
2.26.2
next reply other threads:[~2020-05-23 1:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-23 1:43 John Hubbard [this message]
2020-05-26 19:28 ` [PATCH 1/1] vfio/spapr_tce: convert get_user_pages() --> pin_user_pages() Souptick Joarder
2020-05-26 19:45 ` John Hubbard
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