On 16.08.21 22:52, Peter Xu wrote:
On Thu, Aug 05, 2021 at 11:23:50AM +0200, David Hildenbrand wrote:
When adding RAM_NORESERVE, we forgot to remove the old assertion when
adding the updated one, most probably when reworking the patches or
rebasing. We can easily crash QEMU by adding
-object memory-backend-ram,id=mem0,size=500G,reserve=off
to the QEMU cmdline:
qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
== 0' failed.
Fix it by removing the old assertion.
Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in
qemu_ram_mmap()")
Reviewed-by: Peter Xu <pet...@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
Tested-by: Philippe Mathieu-Daudé <phi...@redhat.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: Peter Xu <pet...@redhat.com>
Cc: Philippe Mathieu-Daudé <phi...@redhat.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
v1 -> v2:
- Added rbs
- Tagged for 6.1 inclusion
---
softmmu/physmem.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 3c1912a1a0..2e18947598 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size,
ram_addr_t max_size,
RAMBlock *new_block;
Error *local_err = NULL;
- assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
RAM_NORESERVE)) == 0);
assert(!host ^ (ram_flags & RAM_PREALLOC));
--
2.31.1
Today I just noticed this patch is still missing for 6.1. How many users are
there with reserve=off? Would it be worth rc4 or not?
Indeed, I forgot to follow up, thanks for bringing this up.
Libvirt does not support virtio-mem yet and consequently doesn't support
reserve=off yet. (there are use cases without virtio-mem, but I don't
think anybody is using it yet)
It's an easy way to crash QEMU, but we could also fix in the -stable
tree instead.
(most probably you and me should also be doing PULL requests for "Memory
API", we'll have to discuss with Paolo)
--
Thanks,
David / dhildenb
