On 29.09.2009, at 02:08, Hollis Blanchard wrote:
On Mon, 2009-07-27 at 12:38 +0200, Alexander Graf wrote:
We currently use host endian long types to store information
in the dirty bitmap.
This works reasonably well on Little Endian targets, because the
u32 after the first contains the next 32 bits. On Big Endian this
breaks completely though, forcing us to be inventive here.
So Ben suggested to always use Little Endian, which looks reasonable.
We only have dirty bitmap implemented in Little Endian targets so far
and since PowerPC would be the first Big Endian platform, we can just
as well switch to Little Endian always with little effort without
breaking existing targets.
Signed-off-by: Alexander Graf <agraf@xxxxxxx>
---
virt/kvm/kvm_main.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 17d8688..3482ad1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -48,6 +48,7 @@
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
+#include <asm-generic/bitops/le.h>
#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
#include "coalesced_mmio.h"
@@ -1656,8 +1657,8 @@ void mark_page_dirty(struct kvm *kvm, gfn_t
gfn)
unsigned long rel_gfn = gfn - memslot->base_gfn;
/* avoid RMW */
- if (!test_bit(rel_gfn, memslot->dirty_bitmap))
- set_bit(rel_gfn, memslot->dirty_bitmap);
+ if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap))
+ generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
}
}
I don't think I've ever exercised the dirty bitmap code, and I don't
really have an opinion. Avi?
No big endian kvm target currently implements dirty bitmaps. In fact,
IIRC only x86 does atm. So by pinning it to LE now, we save ourselves
from much trouble for any later user.
Alex
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