diff mbox series

[PULL,20/42] backends/hostmem: Report error when memory size is unaligned

Message ID 20240608083415.2769160-21-pbonzini@redhat.com
State New
Headers show
Series [PULL,01/42] target/i386: fix pushed value of EFLAGS.RF | expand

Commit Message

Paolo Bonzini June 8, 2024, 8:33 a.m. UTC 
From: Michal Privoznik <mprivozn@redhat.com>

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-backend-file' memory size must be multiple of 2 MiB

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Message-ID: <b5b9f9c6bba07879fb43f3c6f496c69867ae3716.1717584048.git.mprivozn@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/sysemu/hostmem.h |  2 +-
 backends/hostmem-epc.c   |  1 +
 backends/hostmem-file.c  |  1 +
 backends/hostmem-memfd.c |  1 +
 backends/hostmem.c       | 10 ++++++++++
 5 files changed, 14 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 04b884bf42a..de47ae59e4b 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -74,7 +74,7 @@  struct HostMemoryBackend {
     uint64_t size;
     bool merge, dump, use_canonical_path;
     bool prealloc, is_mapped, share, reserve;
-    bool guest_memfd;
+    bool guest_memfd, aligned;
     uint32_t prealloc_threads;
     ThreadContext *prealloc_context;
     DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
diff --git a/backends/hostmem-epc.c b/backends/hostmem-epc.c
index 735e2e1cf84..f58fcf00a10 100644
--- a/backends/hostmem-epc.c
+++ b/backends/hostmem-epc.c
@@ -36,6 +36,7 @@  sgx_epc_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
         return false;
     }
 
+    backend->aligned = true;
     name = object_get_canonical_path(OBJECT(backend));
     ram_flags = (backend->share ? RAM_SHARED : 0) | RAM_PROTECTED;
     return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 3c69db79460..7e5072e33ef 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -80,6 +80,7 @@  file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
         g_assert_not_reached();
     }
 
+    backend->aligned = true;
     name = host_memory_backend_get_name(backend);
     ram_flags = backend->share ? RAM_SHARED : 0;
     ram_flags |= fb->readonly ? RAM_READONLY_FD : 0;
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 745ead0034d..6a3c89a12b2 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -52,6 +52,7 @@  memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
         return false;
     }
 
+    backend->aligned = true;
     name = host_memory_backend_get_name(backend);
     ram_flags = backend->share ? RAM_SHARED : 0;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
diff --git a/backends/hostmem.c b/backends/hostmem.c
index eb9682b4a85..1edc0ede2a5 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -20,6 +20,7 @@ 
 #include "qom/object_interfaces.h"
 #include "qemu/mmap-alloc.h"
 #include "qemu/madvise.h"
+#include "qemu/cutils.h"
 #include "hw/qdev-core.h"
 
 #ifdef CONFIG_NUMA
@@ -325,6 +326,7 @@  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) {
@@ -336,6 +338,14 @@  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 (backend->aligned && !QEMU_IS_ALIGNED(sz, pagesize)) {
+        g_autofree char *pagesize_str = size_to_str(pagesize);
+        error_setg(errp, "backend '%s' memory size must be multiple of %s",
+                   object_get_typename(OBJECT(uc)), pagesize_str);
+        return;
+    }
 
     if (backend->merge) {
         qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE);