linux-kernel - Re: 答复: [PATCH] vfio/pci: make the vfio_pci_mmap

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Message-ID: <20210309124609.GG2356281@nvidia.com>
Date:   Tue, 9 Mar 2021 08:46:09 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Zengtao (B)" <prime.zeng@...ilicon.com>
Cc:     Peter Xu <peterx@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Michel Lespinasse <walken@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Max Gurtovoy <mgurtovoy@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>
Subject: Re: 答复: [PATCH] vfio/pci: make the
 vfio_pci_mmap_fault reentrant

On Tue, Mar 09, 2021 at 03:49:09AM +0000, Zengtao (B) wrote:
> Hi guys:
> 
> Thanks for the helpful comments, after rethinking the issue, I have proposed
>  the following change: 
> 1. follow_pte instead of follow_pfn.

Still no on follow_pfn, you don't need it once you use vmf_insert_pfn

> 2. vmf_insert_pfn loops instead of io_remap_pfn_range
> 3. proper undos when some call fails.
> 4. keep the bigger lock range to avoid unessary pte install. 

Why do we need locks at all here?

Jason