linux-kernel - [PATCH 0/4] vfio/type1: optimize vfio_pin_pages_remote() and vfio_unpin_pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250630072518.31846-1-lizhe.67@bytedance.com>
Date: Mon, 30 Jun 2025 15:25:14 +0800
From: lizhe.67@...edance.com
To: alex.williamson@...hat.com,
	jgg@...pe.ca,
	david@...hat.com,
	peterx@...hat.com
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lizhe.67@...edance.com
Subject: [PATCH 0/4] vfio/type1: optimize vfio_pin_pages_remote() and vfio_unpin_pages_remote() for large folio

From: Li Zhe <lizhe.67@...edance.com>

This patchset is an consolidation of the two previous patchsets[1][2].

When vfio_pin_pages_remote() is called with a range of addresses that
includes large folios, the function currently performs individual
statistics counting operations for each page. This can lead to significant
performance overheads, especially when dealing with large ranges of pages.

The function vfio_unpin_pages_remote() has a similar issue, where executing
put_pfn() for each pfn brings considerable consumption.

This patchset optimizes the performance of the relevant functions by
batching the less efficient operations mentioned before.

The first patch optimizes the performance of the function
vfio_pin_pages_remote(), while the remaining patches optimize the
performance of the function vfio_unpin_pages_remote().

The performance test results, based on v6.16-rc4, for completing the 16G
VFIO MAP/UNMAP DMA, obtained through unit test[3] with slight
modifications[4], are as follows.

Base(6.16-rc4):
./vfio-pci-mem-dma-map 0000:03:00.0 16
------- AVERAGE (MADV_HUGEPAGE) --------
VFIO MAP DMA in 0.047 s (340.2 GB/s)
VFIO UNMAP DMA in 0.135 s (118.6 GB/s)
------- AVERAGE (MAP_POPULATE) --------
VFIO MAP DMA in 0.280 s (57.2 GB/s)
VFIO UNMAP DMA in 0.312 s (51.3 GB/s)
------- AVERAGE (HUGETLBFS) --------
VFIO MAP DMA in 0.052 s (310.5 GB/s)
VFIO UNMAP DMA in 0.136 s (117.3 GB/s)

With this patchset:
------- AVERAGE (MADV_HUGEPAGE) --------
VFIO MAP DMA in 0.027 s (596.4 GB/s)
VFIO UNMAP DMA in 0.045 s (357.6 GB/s)
------- AVERAGE (MAP_POPULATE) --------
VFIO MAP DMA in 0.288 s (55.5 GB/s)
VFIO UNMAP DMA in 0.288 s (55.6 GB/s)
------- AVERAGE (HUGETLBFS) --------
VFIO MAP DMA in 0.031 s (508.3 GB/s)
VFIO UNMAP DMA in 0.045 s (352.9 GB/s)

For large folio, we achieve an over 40% performance improvement for VFIO
MAP DMA and an over 66% performance improvement for VFIO DMA UNMAP. For
small folios, the performance test results show little difference compared
with the performance before optimization.

[1]: https://lore.kernel.org/all/20250529064947.38433-1-lizhe.67@bytedance.com/
[2]: https://lore.kernel.org/all/20250620032344.13382-1-lizhe.67@bytedance.com/
[3]: https://github.com/awilliam/tests/blob/vfio-pci-mem-dma-map/vfio-pci-mem-dma-map.c
[4]: https://lore.kernel.org/all/20250610031013.98556-1-lizhe.67@bytedance.com/

Li Zhe (4):
  vfio/type1: optimize vfio_pin_pages_remote() for large folios
  vfio/type1: batch vfio_find_vpfn() in function
    vfio_unpin_pages_remote()
  vfio/type1: introduce a new member has_rsvd for struct vfio_dma
  vfio/type1: optimize vfio_unpin_pages_remote() for large folio

 drivers/vfio/vfio_iommu_type1.c | 121 ++++++++++++++++++++++++++------
 1 file changed, 100 insertions(+), 21 deletions(-)

-- 
2.20.1