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postcopy: Use temporary for placing zero huge pages

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The kernel can't do UFFDIO_ZEROPAGE for huge pages, so we have
to allocate a temporary (always zero) page and use UFFDIO_COPYPAGE
on it.

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: <20170224182844.32452-9-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 18:28:36 +00:00
parent df9ff5e1e3
commit 41d84210d4
2 changed files with 22 additions and 2 deletions
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1
include/migration/migration.h
View file

@ -109,6 +109,7 @@ struct MigrationIncomingState {
QEMUFile *to_src_file;
QemuMutex rp_mutex; /* We send replies from multiple threads */
void *postcopy_tmp_page;
void *postcopy_tmp_zero_page;
QEMUBH *bh;

23
migration/postcopy-ram.c
View file

@ -324,6 +324,10 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
munmap(mis->postcopy_tmp_page, mis->largest_page_size);
mis->postcopy_tmp_page = NULL;
}
if (mis->postcopy_tmp_zero_page) {
munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size);
mis->postcopy_tmp_zero_page = NULL;
}
trace_postcopy_ram_incoming_cleanup_exit();
return 0;
}
@ -593,8 +597,23 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
return -e;
}
} else {
/* TODO: The kernel can't use UFFDIO_ZEROPAGE for hugepages */
assert(0);
/* The kernel can't use UFFDIO_ZEROPAGE for hugepages */
if (!mis->postcopy_tmp_zero_page) {
mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
int e = errno;
mis->postcopy_tmp_zero_page = NULL;
error_report("%s: %s mapping large zero page",
__func__, strerror(e));
return -e;
}
memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
}
return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page,
pagesize);
}
return 0;