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postcopy: use UFFDIO_ZEROPAGE only when available

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Use a flag on the RAMBlock to state whether it has the
UFFDIO_ZEROPAGE capability, use it when it's available.

This allows the use of postcopy on tmpfs as well as hugepage
backed files.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2018-03-12 17:20:58 +00:00 • committed by Michael S. Tsirkin
parent f90bb71bfd
commit 2ce16640b4
3 changed files with 29 additions and 3 deletions
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16
exec.c
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@ -99,6 +99,11 @@ static MemoryRegion io_mem_unassigned;
*/
#define RAM_RESIZEABLE (1 << 2)
/* UFFDIO_ZEROPAGE is available on this RAMBlock to atomically
* zero the page and wake waiting processes.
* (Set during postcopy)
*/
#define RAM_UF_ZEROPAGE (1 << 3)
#endif
#ifdef TARGET_PAGE_BITS_VARY
@ -1767,6 +1772,17 @@ bool qemu_ram_is_shared(RAMBlock *rb)
return rb->flags & RAM_SHARED;
}
/* Note: Only set at the start of postcopy */
bool qemu_ram_is_uf_zeroable(RAMBlock *rb)
{
return rb->flags & RAM_UF_ZEROPAGE;
}
void qemu_ram_set_uf_zeroable(RAMBlock *rb)
{
rb->flags |= RAM_UF_ZEROPAGE;
}
/* Called with iothread lock held. */
void qemu_ram_set_idstr(RAMBlock *new_block, const char *name, DeviceState *dev)
{