Samuel Thibault
2008-Jan-29 14:12 UTC
[Xen-devel] [PATCH] minios: Fix bug when blkfront reading into zero-mapped buffer
minios: Fix bug when blkfront reading into zero-mapped buffer
by just poking the page.
No need to use virtual_to_mfn() for the ring since that is a real page.
Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>
diff -r 807502236560 extras/mini-os/blkfront.c
--- a/extras/mini-os/blkfront.c Tue Jan 29 14:07:26 2008 +0000
+++ b/extras/mini-os/blkfront.c Tue Jan 29 14:07:32 2008 +0000
@@ -102,7 +102,7 @@ struct blkfront_dev *init_blkfront(char
SHARED_RING_INIT(s);
FRONT_RING_INIT(&dev->ring, s, PAGE_SIZE);
- dev->ring_ref = gnttab_grant_access(0,virtual_to_mfn(s),0);
+ dev->ring_ref = gnttab_grant_access(0,virt_to_mfn(s),0);
evtchn_alloc_unbound_t op;
op.dom = DOMID_SELF;
@@ -288,6 +288,11 @@ void blkfront_aio(struct blkfront_aiocb
for (j = 0; j < n; j++) {
uintptr_t data = start + j * PAGE_SIZE;
+ if (!write) {
+ /* Trigger CoW if needed */
+ *(char*)data = 0;
+ barrier();
+ }
aiocbp->gref[j] = req->seg[j].gref gnttab_grant_access(0,
virtual_to_mfn(data), write);
req->seg[j].first_sect = 0;
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