Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend

From	Stefano Stabellini <sstabellini@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend
Date	2017-03-08 20:10 +0100
Message-ID	<tiP8d-2nO-9@gated-at.bofh.it> (permalink)
References	(1 earlier) <ti7gR-4VX-1@gated-at.bofh.it> <ti7gR-4VX-7@gated-at.bofh.it> <tisv1-3b1-27@gated-at.bofh.it> <tizmN-8ev-7@gated-at.bofh.it> <tiJ2N-6yt-3@gated-at.bofh.it>
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On Wed, 8 Mar 2017, Julien Grall wrote:
> Hi Stefano,
> 
> On 08/03/17 00:49, Stefano Stabellini wrote:
> > On Tue, 7 Mar 2017, Julien Grall wrote:
> > > On 03/06/2017 08:01 PM, Stefano Stabellini wrote:
> > > > +	if (ring->bytes == NULL)
> > > > +		goto error;
> > > > +	for (i = 0; i < (1 << XEN_9PFS_RING_ORDER); i++)
> > > > +		ring->intf->ref[i] =
> > > > gnttab_grant_foreign_access(dev->otherend_id,
> > > > pfn_to_gfn(virt_to_pfn((void*)ring->bytes) + i), 0);.
> > > 
> > > Please use virt_to_gfn rather than pfn_to_gfn(virt_to_pfn).
> > 
> > OK
> > 
> > 
> > > Also, this is not going to work on 64K kernel because you will grant
> > > access to
> > > noncontiguous memory (e.g 0-4K, 64K-68K,...).
> > 
> > By using virt_to_gfn like you suggested, the loop will correctly iterate
> > on a 4K by 4K basis, even on a 64K kernel:
> > 
> >   ring->bytes = (void*)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
> >           XEN_9PFS_RING_ORDER - (PAGE_SHIFT - XEN_PAGE_SHIFT));
> >   for (i = 0; i < (1 << XEN_9PFS_RING_ORDER); i++)
> >       ring->intf->ref[i] = gnttab_grant_foreign_access(dev->otherend_id,
> > virt_to_gfn((void*)ring->bytes) + i, 0);
> 
> BTW, the cast (void *) is not necessary.
> 
> > 
> > where XEN_9PFS_RING_ORDER specifies the order at 4K granularity. Am I
> > missing something?
> 
> I think it is fine. You could move virt_to_gfn(...) outside and avoid to do
> the translation everytime.

All right, thanks.

Thread

[PATCH 0/7] Xen transport for 9pfs frontend driver Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:10 +0100
  [PATCH 1/7] xen: import new ring macros in ring.h Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
    [PATCH 7/7] xen/9pfs: build 9pfs Xen transport driver Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
    [PATCH 6/7] xen/9pfs: receive responses Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
      Re: [PATCH 6/7] xen/9pfs: receive responses Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-07 17:00 +0100
        Re: [PATCH 6/7] xen/9pfs: receive responses Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 02:30 +0100
          Re: [Xen-devel] [PATCH 6/7] xen/9pfs: receive responses Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2017-03-08 21:20 +0100
        Re: [PATCH 6/7] xen/9pfs: receive responses Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 06:30 +0100
          Re: [PATCH 6/7] xen/9pfs: receive responses Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-08 15:40 +0100
            Re: [PATCH 6/7] xen/9pfs: receive responses Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 20:30 +0100
    [PATCH 2/7] xen: introduce the header file for the Xen 9pfs transport protocol Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
      Re: [PATCH 2/7] xen: introduce the header file for the Xen 9pfs  transport protocol Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 22:40 +0100
        Re: [PATCH 2/7] xen: introduce the header file for the Xen 9pfs  transport protocol Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-06 22:50 +0100
      Re: [PATCH 2/7] xen: introduce the header file for the Xen 9pfs  transport protocol Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-06 23:40 +0100
    [PATCH 4/7] xen/9pfs: connect to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
      Re: [PATCH 4/7] xen/9pfs: connect to the backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-07 16:10 +0100
        Re: [PATCH 4/7] xen/9pfs: connect to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 01:30 +0100
          Re: [PATCH 4/7] xen/9pfs: connect to the backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-08 15:00 +0100
            Re: [PATCH 4/7] xen/9pfs: connect to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 20:30 +0100
      Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend Julien Grall <julien.grall@arm.com> - 2017-03-07 20:00 +0100
        Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 03:20 +0100
          Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend Julien Grall <julien.grall@arm.com> - 2017-03-08 13:40 +0100
            Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 20:10 +0100
    [PATCH 3/7] xen/9pfs: introduce Xen 9pfs transport driver Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
    [PATCH 5/7] xen/9pfs: send requests to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-06 21:20 +0100
      Re: [PATCH 5/7] xen/9pfs: send requests to the backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-07 17:40 +0100
        Re: [PATCH 5/7] xen/9pfs: send requests to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 02:00 +0100
          Re: [PATCH 5/7] xen/9pfs: send requests to the backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-08 15:10 +0100
            Re: [PATCH 5/7] xen/9pfs: send requests to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 20:50 +0100
              Re: [PATCH 5/7] xen/9pfs: send requests to the backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-08 21:10 +0100
                Re: [PATCH 5/7] xen/9pfs: send requests to the backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-03-08 22:10 +0100
                Re: [PATCH 5/7] xen/9pfs: send requests to the backend Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 22:30 +0100
    Re: [Xen-devel] [PATCH 1/7] xen: import new ring macros in ring.h Julien Grall <julien.grall@arm.com> - 2017-03-07 20:20 +0100
      Re: [Xen-devel] [PATCH 1/7] xen: import new ring macros in ring.h Stefano Stabellini <sstabellini@kernel.org> - 2017-03-08 01:30 +0100
        Re: [Xen-devel] [PATCH 1/7] xen: import new ring macros in ring.h Julien Grall <julien.grall@arm.com> - 2017-03-08 12:50 +0100
  Re: [Xen-devel] [PATCH 0/7] Xen transport for 9pfs frontend driver Roger Pau Monné <roger.pau@citrix.com> - 2017-03-07 17:50 +0100
    Re: [Xen-devel] [PATCH 0/7] Xen transport for 9pfs frontend driver Stefano Stabellini <sstabellini@kernel.org> - 2017-03-07 19:30 +0100
      Re: [Xen-devel] [PATCH 0/7] Xen transport for 9pfs frontend driver Roger Pau Monné <roger.pau@citrix.com> - 2017-03-09 04:10 +0100
        Re: [Xen-devel] [PATCH 0/7] Xen transport for 9pfs frontend driver Stefano Stabellini <sstabellini@kernel.org> - 2017-03-13 23:40 +0100

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