| Message ID | 58295d1f6c995c0c444e375348436e799689126c.1717140354.git.mprivozn@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | backends/hostmem: Report more errors on failures | expand |
Hi Michal, On 31/5/24 09:29, Michal Privoznik wrote: > If memory-backend-{file,ram} has a size that's not aligned to > underlying page size it is not only wasteful, but also may lead > to hard to debug behaviour. For instance, in case > memory-backend-file and hugepages, madvise() and mbind() fail. > Rightfully so, page is the smallest unit they can work with. And > even though an error is reported, the root cause it not very > clear: > > qemu-system-x86_64: Couldn't set property 'dump' on 'memory-backend-file': Invalid argument > > After this commit: > > qemu-system-x86_64: backend memory size must be multiple of 0x200000 > > Signed-off-by: Michal Privoznik <mprivozn@redhat.com> > --- > backends/hostmem.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/backends/hostmem.c b/backends/hostmem.c > index 012a8c190f..5f9c9ea8f5 100644 > --- a/backends/hostmem.c > +++ b/backends/hostmem.c > @@ -337,6 +337,7 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp) > HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc); > void *ptr; > uint64_t sz; > + size_t pagesize; > bool async = !phase_check(PHASE_LATE_BACKENDS_CREATED); > > if (!bc->alloc) { > @@ -348,6 +349,13 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp) > > ptr = memory_region_get_ram_ptr(&backend->mr); > sz = memory_region_size(&backend->mr); > + pagesize = qemu_ram_pagesize(backend->mr.ram_block); > + > + if (!QEMU_IS_ALIGNED(sz, pagesize)) { > + error_setg(errp, "backend memory size must be multiple of 0x%" > + PRIx64, pagesize); Can we use size_to_str() instead? Also display backend name: "backend '%s' memory size must be multiple of %s" > + return; > + } > > if (backend->merge && > qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE)) {
This patch has been successfully tested by QE. After allocating some hugepages in the host, try to boot up a VM with the memory backed by a file and the size unaligned, check now the message displayed by QEMU: qemu-system-x86_64: backend memory size must be multiple of 0x200000 Tested-by: Mario Casquero <mcasquer@redhat.com> On Fri, May 31, 2024 at 9:29 AM Michal Privoznik <mprivozn@redhat.com> wrote: > > If memory-backend-{file,ram} has a size that's not aligned to > underlying page size it is not only wasteful, but also may lead > to hard to debug behaviour. For instance, in case > memory-backend-file and hugepages, madvise() and mbind() fail. > Rightfully so, page is the smallest unit they can work with. And > even though an error is reported, the root cause it not very > clear: > > qemu-system-x86_64: Couldn't set property 'dump' on 'memory-backend-file': Invalid argument > > After this commit: > > qemu-system-x86_64: backend memory size must be multiple of 0x200000 > > Signed-off-by: Michal Privoznik <mprivozn@redhat.com> > --- > backends/hostmem.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/backends/hostmem.c b/backends/hostmem.c > index 012a8c190f..5f9c9ea8f5 100644 > --- a/backends/hostmem.c > +++ b/backends/hostmem.c > @@ -337,6 +337,7 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp) > HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc); > void *ptr; > uint64_t sz; > + size_t pagesize; > bool async = !phase_check(PHASE_LATE_BACKENDS_CREATED); > > if (!bc->alloc) { > @@ -348,6 +349,13 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp) > > ptr = memory_region_get_ram_ptr(&backend->mr); > sz = memory_region_size(&backend->mr); > + pagesize = qemu_ram_pagesize(backend->mr.ram_block); > + > + if (!QEMU_IS_ALIGNED(sz, pagesize)) { > + error_setg(errp, "backend memory size must be multiple of 0x%" > + PRIx64, pagesize); > + return; > + } > > if (backend->merge && > qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE)) { > -- > 2.44.1 > >
diff --git a/backends/hostmem.c b/backends/hostmem.c index 012a8c190f..5f9c9ea8f5 100644 --- a/backends/hostmem.c +++ b/backends/hostmem.c @@ -337,6 +337,7 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp) HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc); void *ptr; uint64_t sz; + size_t pagesize; bool async = !phase_check(PHASE_LATE_BACKENDS_CREATED); if (!bc->alloc) { @@ -348,6 +349,13 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp) ptr = memory_region_get_ram_ptr(&backend->mr); sz = memory_region_size(&backend->mr); + pagesize = qemu_ram_pagesize(backend->mr.ram_block); + + if (!QEMU_IS_ALIGNED(sz, pagesize)) { + error_setg(errp, "backend memory size must be multiple of 0x%" + PRIx64, pagesize); + return; + } if (backend->merge && qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE)) {
If memory-backend-{file,ram} has a size that's not aligned to underlying page size it is not only wasteful, but also may lead to hard to debug behaviour. For instance, in case memory-backend-file and hugepages, madvise() and mbind() fail. Rightfully so, page is the smallest unit they can work with. And even though an error is reported, the root cause it not very clear: qemu-system-x86_64: Couldn't set property 'dump' on 'memory-backend-file': Invalid argument After this commit: qemu-system-x86_64: backend memory size must be multiple of 0x200000 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- backends/hostmem.c | 8 ++++++++ 1 file changed, 8 insertions(+)