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exec: ram_block_discard_range

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Create ram_block_discard_range in exec.c to replace
postcopy_ram_discard_range and most of ram_discard_range.

Those two routines are a bit of a weird combination, and
ram_discard_range is about to get more complex for hugepages.
It's OS dependent code (so shouldn't be in migration/ram.c) but
it needs quite a bit of the innards of RAMBlock so doesn't belong in
the os*.c.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20170224182844.32452-5-dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2017-02-24 18:28:32 +00:00
parent 29c5917201
commit d3a5038c46
6 changed files with 60 additions and 58 deletions
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54
exec.c
View file

@ -45,6 +45,7 @@
#include "exec/address-spaces.h"
#include "sysemu/xen-mapcache.h"
#include "trace-root.h"
#endif
#include "exec/cpu-all.h"
#include "qemu/rcu_queue.h"
@ -3294,4 +3295,57 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque)
rcu_read_unlock();
return ret;
}
/*
* Unmap pages of memory from start to start+length such that
* they a) read as 0, b) Trigger whatever fault mechanism
* the OS provides for postcopy.
* The pages must be unmapped by the end of the function.
* Returns: 0 on success, none-0 on failure
*
*/
int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
{
int ret = -1;
uint8_t *host_startaddr = rb->host + start;
if ((uintptr_t)host_startaddr & (rb->page_size - 1)) {
error_report("ram_block_discard_range: Unaligned start address: %p",
host_startaddr);
goto err;
}
if ((start + length) <= rb->used_length) {
uint8_t *host_endaddr = host_startaddr + length;
if ((uintptr_t)host_endaddr & (rb->page_size - 1)) {
error_report("ram_block_discard_range: Unaligned end address: %p",
host_endaddr);
goto err;
}
errno = ENOTSUP; /* If we are missing MADVISE etc */
#if defined(CONFIG_MADVISE)
/* Note: We need the madvise MADV_DONTNEED behaviour of definitely
* freeing the page.
*/
ret = madvise(host_startaddr, length, MADV_DONTNEED);
#endif
if (ret) {
ret = -errno;
error_report("ram_block_discard_range: Failed to discard range "
"%s:%" PRIx64 " +%zx (%d)",
rb->idstr, start, length, ret);
}
} else {
error_report("ram_block_discard_range: Overrun block '%s' (%" PRIu64
"/%zx/" RAM_ADDR_FMT")",
rb->idstr, start, length, rb->used_length);
}
err:
return ret;
}
#endif