On 27.11.23 13:32, Michal Privoznik wrote:
Simple reproducer:
qemu.git $ ./build/qemu-system-x86_64 \
-m size=8389632k,slots=16,maxmem=25600000k \
-object
'{"qom-type":"memory-backend-file","id":"ram-node0","mem-path":"/hugepages2M/","prealloc":true,"size":8590983168,"host-nodes":[0],"policy":"bind"}'
\
-numa node,nodeid=0,cpus=0,memdev=ram-node0
With current master I get:
qemu-system-x86_64: cannot bind memory to host NUMA nodes: Invalid argument
The problem is that memory size (8193MiB) is not an integer
multiple of underlying pagesize (2MiB) which triggers a check
inside of madvise(), since we can't really set a madvise() policy
just to a fraction of a page.
I thought we would just always fail create something that doesn't really
make any sense.
Why would we want to support that case?
Let me dig, I thought we would have had some check there at some point
that would make that fail (especially: RAM block not aligned to the
pagesize).
Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
---
backends/hostmem.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 747e7838c0..4e88d048de 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -326,9 +326,10 @@ host_memory_backend_memory_complete(UserCreatable *uc,
Error **errp)
HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc);
Error *local_err = NULL;
void *ptr;
- uint64_t sz;
if (bc->alloc) {
+ uint64_t sz;
+
bc->alloc(backend, &local_err);
if (local_err) {
goto out;
@@ -337,6 +338,11 @@ host_memory_backend_memory_complete(UserCreatable *uc,
Error **errp)
ptr = memory_region_get_ram_ptr(&backend->mr);
sz = memory_region_size(&backend->mr);
+ /* Round up size to be an integer multiple of pagesize, because
+ * madvise() does not really like setting advices on a fraction of a
+ * page. */
+ sz = ROUND_UP(sz, qemu_ram_pagesize(backend->mr.ram_block));
+
if (backend->merge) {
qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE);
}
--
Cheers,
David / dhildenb
