[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend
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. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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