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[Qemu-devel] [PULL 15/19] hostmem-file: add "align" option
From: |
Eduardo Habkost |
Subject: |
[Qemu-devel] [PULL 15/19] hostmem-file: add "align" option |
Date: |
Thu, 18 Jan 2018 00:09:56 -0200 |
From: Haozhong Zhang <address@hidden>
When mmap(2) the backend files, QEMU uses the host page size
(getpagesize(2)) by default as the alignment of mapping address.
However, some backends may require alignments different than the page
size. For example, mmap a device DAX (e.g., /dev/dax0.0) on Linux
kernel 4.13 to an address, which is 4K-aligned but not 2M-aligned,
fails with a kernel message like
[617494.969768] dax dax0.0: qemu-system-x86: dax_mmap: fail, unaligned vma
(0x7fa37c579000 - 0x7fa43c579000, 0x1fffff)
Because there is no common approach to get such alignment requirement,
we add the 'align' option to 'memory-backend-file', so that users or
management utils, which have enough knowledge about the backend, can
specify a proper alignment via this option.
Signed-off-by: Haozhong Zhang <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Eduardo Habkost <address@hidden>
---
docs/nvdimm.txt | 16 ++++++++++++++++
include/exec/memory.h | 3 +++
backends/hostmem-file.c | 41 ++++++++++++++++++++++++++++++++++++++++-
exec.c | 8 +++++++-
memory.c | 2 ++
numa.c | 2 +-
qemu-options.hx | 9 ++++++++-
7 files changed, 77 insertions(+), 4 deletions(-)
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
index 2d9f8c0e8c..21249dd062 100644
--- a/docs/nvdimm.txt
+++ b/docs/nvdimm.txt
@@ -122,3 +122,19 @@ Note:
M >= size of RAM devices +
size of statically plugged vNVDIMM devices +
size of hotplugged vNVDIMM devices
+
+Alignment
+---------
+
+QEMU uses mmap(2) to maps vNVDIMM backends and aligns the mapping
+address to the page size (getpagesize(2)) by default. However, some
+types of backends may require an alignment different than the page
+size. In that case, QEMU v2.12.0 and later provide 'align' option to
+memory-backend-file to allow users to specify the proper alignment.
+
+For example, device dax require the 2 MB alignment, so we can use
+following QEMU command line options to use it (/dev/dax0.0) as the
+backend of vNVDIMM:
+
+ -object
memory-backend-file,id=mem1,share=on,mem-path=/dev/dax0.0,size=4G,align=2M
+ -device nvdimm,id=nvdimm1,memdev=mem1
diff --git a/include/exec/memory.h b/include/exec/memory.h
index a4cabdf44c..07c5d6d597 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -465,6 +465,8 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr,
* @name: Region name, becomes part of RAMBlock name used in migration stream
* must be unique within any device
* @size: size of the region.
+ * @align: alignment of the region base address; if 0, the default alignment
+ * (getpagesize()) will be used.
* @share: %true if memory must be mmaped with the MAP_SHARED flag
* @path: the path in which to allocate the RAM.
* @errp: pointer to Error*, to store an error if it happens.
@@ -476,6 +478,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
struct Object *owner,
const char *name,
uint64_t size,
+ uint64_t align,
bool share,
const char *path,
Error **errp);
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index e44c319915..e319ec1ad8 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -34,6 +34,7 @@ struct HostMemoryBackendFile {
bool share;
bool discard_data;
char *mem_path;
+ uint64_t align;
};
static void
@@ -58,7 +59,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error
**errp)
path = object_get_canonical_path(OBJECT(backend));
memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
path,
- backend->size, fb->share,
+ backend->size, fb->align, fb->share,
fb->mem_path, errp);
g_free(path);
}
@@ -115,6 +116,40 @@ static void file_memory_backend_set_discard_data(Object
*o, bool value,
MEMORY_BACKEND_FILE(o)->discard_data = value;
}
+static void file_memory_backend_get_align(Object *o, Visitor *v,
+ const char *name, void *opaque,
+ Error **errp)
+{
+ HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
+ uint64_t val = fb->align;
+
+ visit_type_size(v, name, &val, errp);
+}
+
+static void file_memory_backend_set_align(Object *o, Visitor *v,
+ const char *name, void *opaque,
+ Error **errp)
+{
+ HostMemoryBackend *backend = MEMORY_BACKEND(o);
+ HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
+ Error *local_err = NULL;
+ uint64_t val;
+
+ if (host_memory_backend_mr_inited(backend)) {
+ error_setg(&local_err, "cannot change property value");
+ goto out;
+ }
+
+ visit_type_size(v, name, &val, &local_err);
+ if (local_err) {
+ goto out;
+ }
+ fb->align = val;
+
+ out:
+ error_propagate(errp, local_err);
+}
+
static void file_backend_unparent(Object *obj)
{
HostMemoryBackend *backend = MEMORY_BACKEND(obj);
@@ -145,6 +180,10 @@ file_backend_class_init(ObjectClass *oc, void *data)
object_class_property_add_str(oc, "mem-path",
get_mem_path, set_mem_path,
&error_abort);
+ object_class_property_add(oc, "align", "int",
+ file_memory_backend_get_align,
+ file_memory_backend_set_align,
+ NULL, NULL, &error_abort);
}
static void file_backend_instance_finalize(Object *o)
diff --git a/exec.c b/exec.c
index d28fc0cd3d..00055559b8 100644
--- a/exec.c
+++ b/exec.c
@@ -1612,7 +1612,13 @@ static void *file_ram_alloc(RAMBlock *block,
void *area;
block->page_size = qemu_fd_getpagesize(fd);
- block->mr->align = block->page_size;
+ if (block->mr->align % block->page_size) {
+ error_setg(errp, "aligment 0x%" PRIx64
+ " must be multiples of page size 0x%" PRIx64,
+ block->mr->align, block->page_size);
+ return NULL;
+ }
+ block->mr->align = MAX(block->page_size, block->mr->align);
#if defined(__s390x__)
if (kvm_enabled()) {
block->mr->align = MAX(block->mr->align, QEMU_VMALLOC_ALIGN);
diff --git a/memory.c b/memory.c
index 4b41fb837b..449a1429b9 100644
--- a/memory.c
+++ b/memory.c
@@ -1570,6 +1570,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
struct Object *owner,
const char *name,
uint64_t size,
+ uint64_t align,
bool share,
const char *path,
Error **errp)
@@ -1578,6 +1579,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr,
mr->ram = true;
mr->terminates = true;
mr->destructor = memory_region_destructor_ram;
+ mr->align = align;
mr->ram_block = qemu_ram_alloc_from_file(size, mr, share, path, errp);
mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0;
}
diff --git a/numa.c b/numa.c
index 7b9c33ad12..83675a03f3 100644
--- a/numa.c
+++ b/numa.c
@@ -456,7 +456,7 @@ static void allocate_system_memory_nonnuma(MemoryRegion
*mr, Object *owner,
if (mem_path) {
#ifdef __linux__
Error *err = NULL;
- memory_region_init_ram_from_file(mr, owner, name, ram_size, false,
+ memory_region_init_ram_from_file(mr, owner, name, ram_size, 0, false,
mem_path, &err);
if (err) {
error_report_err(err);
diff --git a/qemu-options.hx b/qemu-options.hx
index b3e03c5464..5ff741a4af 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3974,7 +3974,7 @@ property must be set. These objects are placed in the
@table @option
address@hidden -object
memory-backend-file,address@hidden,address@hidden,address@hidden,address@hidden|off},address@hidden|off},address@hidden|off},address@hidden|off},address@hidden|off},address@hidden,address@hidden|preferred|bind|interleave}
address@hidden -object
memory-backend-file,address@hidden,address@hidden,address@hidden,address@hidden|off},address@hidden|off},address@hidden|off},address@hidden|off},address@hidden|off},address@hidden,address@hidden|preferred|bind|interleave},address@hidden
Creates a memory file backend object, which can be used to back
the guest RAM with huge pages.
@@ -4027,6 +4027,13 @@ restrict memory allocation to the given host node list
interleave memory allocations across the given host node list
@end table
+The @option{align} option specifies the base address alignment when
+QEMU mmap(2) @option{mem-path}, and accepts common suffixes, eg
address@hidden Some backend store specified by @option{mem-path}
+requires an alignment different than the default one used by QEMU, eg
+the device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In
+such cases, users can specify the required alignment via this option.
+
@item -object
memory-backend-ram,address@hidden,address@hidden|off},address@hidden|off},address@hidden|off},address@hidden,address@hidden,address@hidden|preferred|bind|interleave}
Creates a memory backend object, which can be used to back the guest RAM.
--
2.14.3
- [Qemu-devel] [PULL 07/19] hw/arm/virt: Allow only supported dynamic sysbus devices, (continued)
- [Qemu-devel] [PULL 07/19] hw/arm/virt: Allow only supported dynamic sysbus devices, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 06/19] machine: Replace has_dynamic_sysbus with list of allowed devices, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 08/19] ppc: e500: Allow only supported dynamic sysbus devices, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 09/19] spapr: Allow only supported dynamic sysbus devices, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 10/19] xen: Add only xen-sysdev to dynamic sysbus device list, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 11/19] q35: Allow only supported dynamic sysbus devices, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 13/19] qdev: Check for the availability of a hotplug controller before adding a device, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 12/19] qdev_monitor: Simplify error handling in qdev_device_add(), Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 14/19] scripts: Remove fixed entries from the device-crash-test, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 17/19] nvdimm: add 'unarmed' option, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 15/19] hostmem-file: add "align" option,
Eduardo Habkost <=
- [Qemu-devel] [PULL 16/19] nvdimm: add a macro for property "label-size", Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 18/19] possible_cpus: add CPUArchId::type field, Eduardo Habkost, 2018/01/17
- [Qemu-devel] [PULL 19/19] fw_cfg: fix memory corruption when all fw_cfg slots are used, Eduardo Habkost, 2018/01/17
- Re: [Qemu-devel] [PULL 00/19] machine queue, 2018-01-18, Peter Maydell, 2018/01/18