linux-kernel - Re: [PATCH v2 0/3] vfio/type1: Batch page pinning

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Date:   Tue, 23 Feb 2021 11:24:27 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Cornelia Huck <cohuck@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Matthew Wilcox <willy@...radead.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Steven Sistare <steven.sistare@...cle.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] vfio/type1: Batch page pinning

On Fri, 19 Feb 2021 11:13:02 -0500
Daniel Jordan <daniel.m.jordan@...cle.com> wrote:

> v2:
>  - Fixed missing error unwind in patch 3 (Alex).  After more thought,
>    the ENODEV case is fine, so it stayed the same.
> 
>  - Rebased on linux-vfio.git/next (no conflicts).
> 
> ---
> 
> The VFIO type1 driver is calling pin_user_pages_remote() once per 4k page, so
> let's do it once per 512 4k pages to bring VFIO in line with other drivers such
> as IB and vDPA.
> 
> qemu guests with at least 2G memory start about 8% faster on a Xeon server,
> with more detailed results in the last changelog.
> 
> Thanks to Matthew, who first suggested the idea to me.
> 
> Daniel
> 
> 
> Test Cases
> ----------
> 
>  1) qemu passthrough with IOMMU-capable PCI device
> 
>  2) standalone program to hit
>         vfio_pin_map_dma() -> vfio_pin_pages_remote()
> 
>  3) standalone program to hit
>         vfio_iommu_replay() -> vfio_pin_pages_remote()
> 
> Each was run...
> 
>  - with varying sizes
>  - with/without disable_hugepages=1
>  - with/without LOCKED_VM exceeded
> 
> I didn't test vfio_pin_page_external() because there was no readily available
> hardware, but the changes there are pretty minimal.
> 
> Daniel Jordan (3):
>   vfio/type1: Change success value of vaddr_get_pfn()
>   vfio/type1: Prepare for batched pinning with struct vfio_batch
>   vfio/type1: Batch page pinning
> 
>  drivers/vfio/vfio_iommu_type1.c | 215 +++++++++++++++++++++++---------
>  1 file changed, 155 insertions(+), 60 deletions(-)
> 
> base-commit: 76adb20f924f8d27ed50d02cd29cadedb59fd88f

Applied to vfio next branch for v5.12.  Thanks,

Alex