On 25/04/2016 13:55, Dominik Dingel wrote:
> While in the anonymous ram case we already take care of the right alignment
> such an alignment gurantee does not exist for file backed ram allocation.
>
> Instead, pagesize is used for alignment. On s390 this is not enough for gmap,
> as we need to satisfy an alignment up to segments.
>
> Reported-by: Halil Pasic <pa...@linux.vnet.ibm.com>
> Signed-off-by: Dominik Dingel <din...@linux.vnet.ibm.com>
Looks good now, thanks.
Cc: qemu-stable <qemu-sta...@nongnu.org>
Paolo
> ---
>
> v2 -> v3:
> Skipping additional variable and just use alignment of memory region.
> As memory will not be backpropagated it is enough to round up to page_sizes.
>
> v1 -> v2:
> While enforcing alignments we allow memory sizes on page_size.
> On mmap the memory size will be round up to alignments.
>
> I thought about moving this alignment into qemu_ram_mmap but the result
> was a lot of code churn, the other possibility was to create an additional
> define ending up with two defines with the same semantics.
> ---
> exec.c | 5 +++--
> include/qemu/osdep.h | 13 +++++++++++++
> util/oslib-posix.c | 13 -------------
> 3 files changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index c4f9036..fc75266 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1296,7 +1296,7 @@ static void *file_ram_alloc(RAMBlock *block,
> }
>
> page_size = qemu_fd_getpagesize(fd);
> - block->mr->align = page_size;
> + block->mr->align = MAX(page_size, QEMU_VMALLOC_ALIGN);
>
> if (memory < page_size) {
> error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
> @@ -1317,7 +1317,8 @@ static void *file_ram_alloc(RAMBlock *block,
> perror("ftruncate");
> }
>
> - area = qemu_ram_mmap(fd, memory, page_size, block->flags & RAM_SHARED);
> + area = qemu_ram_mmap(fd, memory, block->mr->align,
> + block->flags & RAM_SHARED);
> if (area == MAP_FAILED) {
> error_setg_errno(errp, errno,
> "unable to map backing store for guest RAM");
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 408783f..783270f 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -247,6 +247,19 @@ void qemu_anon_ram_free(void *ptr, size_t size);
>
> #endif
>
> +#if defined(__linux__) && \
> + (defined(__x86_64__) || defined(__arm__) || defined(__aarch64__))
> + /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
> + Valgrind does not support alignments larger than 1 MiB,
> + therefore we need special code which handles running on Valgrind. */
> +# define QEMU_VMALLOC_ALIGN (512 * 4096)
> +#elif defined(__linux__) && defined(__s390x__)
> + /* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
> +# define QEMU_VMALLOC_ALIGN (256 * 4096)
> +#else
> +# define QEMU_VMALLOC_ALIGN getpagesize()
> +#endif
> +
> int qemu_madvise(void *addr, size_t len, int advice);
>
> int qemu_open(const char *name, int flags, ...);
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index 6cc4b8f..4adde93 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -26,19 +26,6 @@
> * THE SOFTWARE.
> */
>
> -#if defined(__linux__) && \
> - (defined(__x86_64__) || defined(__arm__) || defined(__aarch64__))
> - /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
> - Valgrind does not support alignments larger than 1 MiB,
> - therefore we need special code which handles running on Valgrind. */
> -# define QEMU_VMALLOC_ALIGN (512 * 4096)
> -#elif defined(__linux__) && defined(__s390x__)
> - /* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
> -# define QEMU_VMALLOC_ALIGN (256 * 4096)
> -#else
> -# define QEMU_VMALLOC_ALIGN getpagesize()
> -#endif
> -
> #include "qemu/osdep.h"
> #include <termios.h>
> #include <termios.h>
>
