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Re: [Qemu-devel] [PATCH] exec.c: Ensure right alignment also for file ba
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH] exec.c: Ensure right alignment also for file backed ram |
Date: |
Tue, 3 May 2016 08:57:33 +0800 |
User-agent: |
Mutt/1.6.0 (2016-04-01) |
On Fri, 04/29 10:26, Dominik Dingel wrote:
> On Fri, 29 Apr 2016 15:32:22 +0800
> Fam Zheng <address@hidden> wrote:
>
> > On Mon, 04/25 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.
> >
> > s/gurantee/guarantee/
> >
> > Otherwise looks good to me,
> >
> > Reviewed-by: Fam Zheng <address@hidden>
>
> Thank you very much!
>
> Paolo do you want me to fix the typo, add the r-b and resend the patch?
Paolo is still travelling this week, you can do that if you feel like to, or I
guess he can fix it himself when applying later.
Fam
>
> > >
> > > 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 <address@hidden>
> > > Signed-off-by: Dominik Dingel <address@hidden>
> > >
> > > ---
> > >
> > > 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>
> > > --
> > > 2.6.6
> > >
> > >
> >
>
- Re: [Qemu-devel] [PATCH] exec.c: Ensure right alignment also for file backed ram,
Fam Zheng <=