On Thu, Mar 29, 2018 at 04:25:37PM +1100, David Gibson wrote:
> There are a couple places (one generic, one target specific) where we need
> to get the host page size associated with a particular memory backend. I
> have some upcoming code which will add another place which wants this. So,
> for convenience, add a helper function to calculate this.
>
> host_memory_backend_pagesize() returns the host pagesize for a given
> HostMemoryBackend object, or for the default backend (-mem-path) if passed
> NULL.
>
> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> backends/hostmem.c | 20 ++++++++++++++++++++
> exec.c | 21 +++++----------------
> include/sysemu/hostmem.h | 2 ++
> target/ppc/kvm.c | 10 +---------
> 4 files changed, 28 insertions(+), 25 deletions(-)
>
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> index f61093654e..b6a60cfc5d 100644
> --- a/backends/hostmem.c
> +++ b/backends/hostmem.c
> @@ -18,6 +18,7 @@
> #include "qapi/visitor.h"
> #include "qemu/config-file.h"
> #include "qom/object_interfaces.h"
> +#include "qemu/mmap-alloc.h"
>
> #ifdef CONFIG_NUMA
> #include <numaif.h>
> @@ -262,6 +263,25 @@ bool host_memory_backend_is_mapped(HostMemoryBackend
> *backend)
> return backend->is_mapped;
> }
>
> +long host_memory_backend_pagesize(HostMemoryBackend *memdev)
qemu_mempath_getpagesize() returns size_t. Why are you using
long here?
> +{
> + const char *path = NULL;
> +
> +#ifdef __linux__
> + if (memdev) {
> + path = object_property_get_str(OBJECT(memdev), "mem-path", NULL);
> + } else {
> + path = mem_path;
> + }
> +#endif
> +
> + if (path) {
> + return qemu_mempath_getpagesize(path);
> + } else {
> + return getpagesize();
Isn't it simpler to make qemu_mempath_getpagesize() handle
path==NULL?
> + }
> +}
> +
> static void
> host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
> {
> diff --git a/exec.c b/exec.c
> index c09bd93df3..04856c2402 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1488,18 +1488,13 @@ void ram_block_dump(Monitor *mon)
> */
> static int find_max_supported_pagesize(Object *obj, void *opaque)
> {
> - char *mem_path;
> long *hpsize_min = opaque;
>
> if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND)) {
> - mem_path = object_property_get_str(obj, "mem-path", NULL);
> - if (mem_path) {
> - long hpsize = qemu_mempath_getpagesize(mem_path);
> - if (hpsize < *hpsize_min) {
> - *hpsize_min = hpsize;
> - }
> - } else {
> - *hpsize_min = getpagesize();
> + long hpsize = host_memory_backend_pagesize(MEMORY_BACKEND(obj));
So in this caller, `backend` is always non-NULL...
> +
> + if (hpsize < *hpsize_min) {
> + *hpsize_min = hpsize;
> }
> }
>
> @@ -1509,15 +1504,9 @@ static int find_max_supported_pagesize(Object *obj,
> void *opaque)
> long qemu_getrampagesize(void)
> {
> long hpsize = LONG_MAX;
> - long mainrampagesize;
> + long mainrampagesize = host_memory_backend_pagesize(NULL);
...on this caller `backend` is always NULL...
> Object *memdev_root;
>
> - if (mem_path) {
> - mainrampagesize = qemu_mempath_getpagesize(mem_path);
> - } else {
> - mainrampagesize = getpagesize();
> - }
> -
> /* it's possible we have memory-backend objects with
> * hugepage-backed RAM. these may get mapped into system
> * address space via -numa parameters or memory hotplug
[...]
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index b329cd8173..0adcf18c9f 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -493,15 +493,7 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
> bool kvmppc_is_mem_backend_page_size_ok(const char *obj_path)
> {
> Object *mem_obj = object_resolve_path(obj_path, NULL);
> - char *mempath = object_property_get_str(mem_obj, "mem-path", NULL);
> - long pagesize;
> -
> - if (mempath) {
> - pagesize = qemu_mempath_getpagesize(mempath);
> - g_free(mempath);
> - } else {
> - pagesize = getpagesize();
> - }
> + long pagesize = host_memory_backend_pagesize(MEMORY_BACKEND(mem_obj));
>
...and here `backend` is always non-NULL.
If there's no caller that relies on both code paths, why overload
a single function for two different operations?
I would simply make qemu_mempath_getpagesize() work if path is
NULL, use qemu_mempath_getpagesize(mem_path) at
qemu_getrampagesize(), and make host_memory_backend_pagesize()
assume require a non-NULL `memdev`.
> +long host_memory_backend_pagesize(HostMemoryBackend *memdev)
Why is the code duplicated in target/ppc/kvm.c?
> +{
> + const char *path = NULL;
> +
> +#ifdef __linux__
> + if (memdev) {
> + path = object_property_get_str(OBJECT(memdev), "mem-path", NULL);
> + } else {
> + path = mem_path;
> + }
> +#endif
> +
> + if (path) {
> + return qemu_mempath_getpagesize(path);
> + } else {
> + return getpagesize();
> + }
> +}
> +
> return pagesize >= max_cpu_page_size;
> }
> --
> 2.14.3
>
--
Eduardo
