OpenE2K/qemu-e2k
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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
View File

@ -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)
{

3
include/exec/cpu-common.h
View File

@ -73,6 +73,9 @@ void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev);
void qemu_ram_unset_idstr(RAMBlock *block);
const char *qemu_ram_get_idstr(RAMBlock *rb);
bool qemu_ram_is_shared(RAMBlock *rb);
bool qemu_ram_is_uf_zeroable(RAMBlock *rb);
void qemu_ram_set_uf_zeroable(RAMBlock *rb);
size_t qemu_ram_pagesize(RAMBlock *block);
size_t qemu_ram_pagesize_largest(void);

13
migration/postcopy-ram.c
View File

@ -481,6 +481,10 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr,
error_report("%s userfault: Region doesn't support COPY", __func__);
return -1;
}
if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) {
RAMBlock *rb = qemu_ram_block_by_name(block_name);
qemu_ram_set_uf_zeroable(rb);
}
return 0;
}
@ -700,11 +704,14 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
RAMBlock *rb)
{
size_t pagesize = qemu_ram_pagesize(rb);
trace_postcopy_place_page_zero(host);
if (qemu_ram_pagesize(rb) == getpagesize()) {
if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, getpagesize(),
rb)) {
/* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE
* but it's not available for everything (e.g. hugetlbpages)
*/
if (qemu_ram_is_uf_zeroable(rb)) {
if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) {
int e = errno;
error_report("%s: %s zero host: %p",
__func__, strerror(e), host);