Re: [PATCH v5 01/50] multi-process: memory: alloc RAM from file at offset

[Jag Raman]

On 3/3/2020 2:51 PM, Dr. David Alan Gilbert wrote:
> * Jagannathan Raman (address@hidden) wrote:
> > Allow RAM MemoryRegion to be created from an offset in a file, instead
> > of allocating at offset of 0 by default. This is needed to synchronize
> > RAM between QEMU & remote process.
> > This will be needed for the following patches.
> >
> > Signed-off-by: Jagannathan Raman <address@hidden>
> > Signed-off-by: John G Johnson <address@hidden>
> > Signed-off-by: Elena Ufimtseva <address@hidden>
>
> This looks reasonable to me, so :
>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
>
> but can I suggest you take simple things like this and split them out
> into a separate little series;  I think people would probably take them
> even though the current users have a 0 offset.

Thanks Dave! We'll split these out of the series and integrate them
first.

--
Jag

> Dave
>
> > ---
> >   exec.c                    | 11 +++++++----
> >   include/exec/ram_addr.h   |  2 +-
> >   include/qemu/mmap-alloc.h |  3 ++-
> >   memory.c                  |  2 +-
> >   util/mmap-alloc.c         |  7 ++++---
> >   util/oslib-posix.c        |  2 +-
> >   6 files changed, 16 insertions(+), 11 deletions(-)
> >
> > diff --git a/exec.c b/exec.c
> > index c930040..e524185 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -1841,6 +1841,7 @@ static void *file_ram_alloc(RAMBlock *block,
> >                               ram_addr_t memory,
> >                               int fd,
> >                               bool truncate,
> > +                            off_t offset,
> >                               Error **errp)
> >   {
> >       Error *err = NULL;
> > @@ -1893,7 +1894,8 @@ static void *file_ram_alloc(RAMBlock *block,
> >       }
> >   
> >       area = qemu_ram_mmap(fd, memory, block->mr->align,
> > -                         block->flags & RAM_SHARED, block->flags & RAM_PMEM);
> > +                         block->flags & RAM_SHARED, block->flags & RAM_PMEM,
> > +                         offset);
> >       if (area == MAP_FAILED) {
> >           error_setg_errno(errp, errno,
> >                            "unable to map backing store for guest RAM");
> > @@ -2322,7 +2324,7 @@ static void ram_block_add(RAMBlock *new_block, Error 
> > **errp, bool shared)
> >   #ifdef CONFIG_POSIX
> >   RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
> >                                    uint32_t ram_flags, int fd,
> > -                                 Error **errp)
> > +                                 off_t offset, Error **errp)
> >   {
> >       RAMBlock *new_block;
> >       Error *local_err = NULL;
> > @@ -2367,7 +2369,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, 
> > MemoryRegion *mr,
> >       new_block->used_length = size;
> >       new_block->max_length = size;
> >       new_block->flags = ram_flags;
> > -    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp);
> > +    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, offset,
> > +                                     errp);
> >       if (!new_block->host) {
> >           g_free(new_block);
> >           return NULL;
> > @@ -2397,7 +2400,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, 
> > MemoryRegion *mr,
> >           return NULL;
> >       }
> >   
> > -    block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, errp);
> > +    block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, 0, errp);
> >       if (!block) {
> >           if (created) {
> >               unlink(mem_path);
> > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> > index 5e59a3d..1b9f489 100644
> > --- a/include/exec/ram_addr.h
> > +++ b/include/exec/ram_addr.h
> > @@ -121,7 +121,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, 
> > MemoryRegion *mr,
> >                                      Error **errp);
> >   RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
> >                                    uint32_t ram_flags, int fd,
> > -                                 Error **errp);
> > +                                 off_t offset, Error **errp);
> >   
> >   RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
> >                                     MemoryRegion *mr, Error **errp);
> > diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
> > index e786266..4f57985 100644
> > --- a/include/qemu/mmap-alloc.h
> > +++ b/include/qemu/mmap-alloc.h
> > @@ -25,7 +25,8 @@ void *qemu_ram_mmap(int fd,
> >                       size_t size,
> >                       size_t align,
> >                       bool shared,
> > -                    bool is_pmem);
> > +                    bool is_pmem,
> > +                    off_t start);
> >   
> >   void qemu_ram_munmap(int fd, void *ptr, size_t size);
> >   
> > diff --git a/memory.c b/memory.c
> > index aeaa8dc..131bc6c 100644
> > --- a/memory.c
> > +++ b/memory.c
> > @@ -1595,7 +1595,7 @@ void memory_region_init_ram_from_fd(MemoryRegion *mr,
> >       mr->destructor = memory_region_destructor_ram;
> >       mr->ram_block = qemu_ram_alloc_from_fd(size, mr,
> >                                              share ? RAM_SHARED : 0,
> > -                                           fd, &err);
> > +                                           fd, 0, &err);
> >       mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0;
> >       if (err) {
> >           mr->size = int128_zero();
> > diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> > index 27dcccd..a28f702 100644
> > --- a/util/mmap-alloc.c
> > +++ b/util/mmap-alloc.c
> > @@ -86,7 +86,8 @@ void *qemu_ram_mmap(int fd,
> >                       size_t size,
> >                       size_t align,
> >                       bool shared,
> > -                    bool is_pmem)
> > +                    bool is_pmem,
> > +                    off_t start)
> >   {
> >       int flags;
> >       int map_sync_flags = 0;
> > @@ -147,7 +148,7 @@ void *qemu_ram_mmap(int fd,
> >       offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
> >   
> >       ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
> > -               flags | map_sync_flags, fd, 0);
> > +               flags | map_sync_flags, fd, start);
> >   
> >       if (ptr == MAP_FAILED && map_sync_flags) {
> >           if (errno == ENOTSUP) {
> > @@ -172,7 +173,7 @@ void *qemu_ram_mmap(int fd,
> >            * we will remove these flags to handle compatibility.
> >            */
> >           ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
> > -                   flags, fd, 0);
> > +                   flags, fd, start);
> >       }
> >   
> >       if (ptr == MAP_FAILED) {
> > diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> > index 5a291cc..bd221dd 100644
> > --- a/util/oslib-posix.c
> > +++ b/util/oslib-posix.c
> > @@ -205,7 +205,7 @@ void *qemu_memalign(size_t alignment, size_t size)
> >   void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
> >   {
> >       size_t align = QEMU_VMALLOC_ALIGN;
> > -    void *ptr = qemu_ram_mmap(-1, size, align, shared, false);
> > +    void *ptr = qemu_ram_mmap(-1, size, align, shared, false, 0);
> >   
> >       if (ptr == MAP_FAILED) {
> >           return NULL;
> > --
> > 1.8.3.1
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK