From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35112) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b07X3-0005Ng-CB for qemu-devel@nongnu.org; Tue, 10 May 2016 09:17:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b07X0-0002eQ-Rs for qemu-devel@nongnu.org; Tue, 10 May 2016 09:17:00 -0400 Sender: Paolo Bonzini References: <1461585338-45863-1-git-send-email-dingel@linux.vnet.ibm.com> From: Paolo Bonzini Message-ID: <5731DF3F.3060902@redhat.com> Date: Tue, 10 May 2016 15:16:47 +0200 MIME-Version: 1.0 In-Reply-To: <1461585338-45863-1-git-send-email-dingel@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] exec.c: Ensure right alignment also for file backed ram List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dominik Dingel , qemu-devel@nongnu.org Cc: Peter Crosthwaite , Richard Henderson , Halil Pasic , qemu-stable 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 > Signed-off-by: Dominik Dingel Looks good now, thanks. Cc: qemu-stable 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 > #include >