linux-kernel - Re: [PATCH] vfio/pci: Handle concurrent vma faults

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Message-ID: <20210310200607.GG6530@xz-x1>
Date:   Wed, 10 Mar 2021 15:06:07 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, prime.zeng@...ilicon.com,
        cohuck@...hat.com
Subject: Re: [PATCH] vfio/pci: Handle concurrent vma faults

On Wed, Mar 10, 2021 at 02:40:11PM -0400, Jason Gunthorpe wrote:
> On Wed, Mar 10, 2021 at 11:34:06AM -0700, Alex Williamson wrote:
> 
> > > I think after the address_space changes this should try to stick with
> > > a normal io_rmap_pfn_range() done outside the fault handler.
> > 
> > I assume you're suggesting calling io_remap_pfn_range() when device
> > memory is enabled,
> 
> Yes, I think I saw Peter thinking along these lines too
> 
> Then fault just always causes SIGBUS if it gets called

Indeed that looks better than looping in the fault().

But I don't know whether it'll be easy to move io_remap_pfn_range() to device
memory enablement.  If it's a two-step thing, we can fix the BUG_ON and vma
duplication issue first, then the full rework can be done in the bigger series
as what be chosen as the last approach.

Thanks,

-- 
Peter Xu