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xen_backend: add an emulation of grant copy

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Not all Xen environments support the xengnttab_grant_copy() operation.
E.g. where the OS is FreeBSD or Xen is older than 4.8.0.

This patch introduces an emulation of that operation using
xengnttab_map_domain_grant_refs() and memcpy() for those environments.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
This commit is contained in:
Paul Durrant 2018-05-17 16:35:54 +01:00 committed by Stefano Stabellini
parent 58560f2ae7
commit 3fe12b8403
1 changed files with 53 additions and 0 deletions
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53
hw/xen/xen_backend.c
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@ -146,6 +146,55 @@ void xen_be_unmap_grant_refs(struct XenDevice *xendev, void *ptr,
}
}
static int compat_copy_grant_refs(struct XenDevice *xendev,
bool to_domain,
XenGrantCopySegment segs[],
unsigned int nr_segs)
{
uint32_t *refs = g_new(uint32_t, nr_segs);
int prot = to_domain ? PROT_WRITE : PROT_READ;
void *pages;
unsigned int i;
for (i = 0; i < nr_segs; i++) {
XenGrantCopySegment *seg = &segs[i];
refs[i] = to_domain ?
seg->dest.foreign.ref : seg->source.foreign.ref;
}
pages = xengnttab_map_domain_grant_refs(xendev->gnttabdev, nr_segs,
xen_domid, refs, prot);
if (!pages) {
xen_pv_printf(xendev, 0,
"xengnttab_map_domain_grant_refs failed: %s\n",
strerror(errno));
g_free(refs);
return -1;
}
for (i = 0; i < nr_segs; i++) {
XenGrantCopySegment *seg = &segs[i];
void *page = pages + (i * XC_PAGE_SIZE);
if (to_domain) {
memcpy(page + seg->dest.foreign.offset, seg->source.virt,
seg->len);
} else {
memcpy(seg->dest.virt, page + seg->source.foreign.offset,
seg->len);
}
}
if (xengnttab_unmap(xendev->gnttabdev, pages, nr_segs)) {
xen_pv_printf(xendev, 0, "xengnttab_unmap failed: %s\n",
strerror(errno));
}
g_free(refs);
return 0;
}
int xen_be_copy_grant_refs(struct XenDevice *xendev,
bool to_domain,
XenGrantCopySegment segs[],
@ -157,6 +206,10 @@ int xen_be_copy_grant_refs(struct XenDevice *xendev,
assert(xendev->ops->flags & DEVOPS_FLAG_NEED_GNTDEV);
if (!xen_feature_grant_copy) {
return compat_copy_grant_refs(xendev, to_domain, segs, nr_segs);
}
xengnttab_segs = g_new0(xengnttab_grant_copy_segment_t, nr_segs);
for (i = 0; i < nr_segs; i++) {