On Thu, Jul 14, 2022 at 11:30:11AM +0200, Hanna Reitz wrote: > On 08.07.22 06:17, Stefan Hajnoczi wrote: > > Emulated devices and other BlockBackend users wishing to take advantage > > of blk_register_buf() all have the same repetitive job: register > > RAMBlocks with the BlockBackend using RAMBlockNotifier. > > > > Add a BlockRAMRegistrar API to do this. A later commit will use this > > from hw/block/virtio-blk.c. > > > > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> > > --- > > MAINTAINERS | 1 + > > include/sysemu/block-ram-registrar.h | 30 +++++++++++++++++++++ > > block/block-ram-registrar.c | 39 ++++++++++++++++++++++++++++ > > block/meson.build | 1 + > > 4 files changed, 71 insertions(+) > > create mode 100644 include/sysemu/block-ram-registrar.h > > create mode 100644 block/block-ram-registrar.c > > What memory is handled in ram_list? Is it everything? If so, won’t devices > have trouble registering all those buffer, especially if they happen to be > fragmented in physical memory? (nvme_register_buf() seems to say it can run > out of slots quite easily.)
I replied to this in another sub-thread. You are right, there is a possibility of running out of mappings and there's no smart resource management at the moment. > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 50f340d9ee..d16189449f 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -2490,6 +2490,7 @@ F: block* > > F: block/ > > F: hw/block/ > > F: include/block/ > > +F: include/sysemu/block-*.h > > F: qemu-img* > > F: docs/tools/qemu-img.rst > > F: qemu-io* > > Sneaky. ;) > > > diff --git a/include/sysemu/block-ram-registrar.h > > b/include/sysemu/block-ram-registrar.h > > new file mode 100644 > > index 0000000000..09d63f64b2 > > --- /dev/null > > +++ b/include/sysemu/block-ram-registrar.h > > @@ -0,0 +1,30 @@ > > +/* > > + * BlockBackend RAM Registrar > > + * > > + * SPDX-License-Identifier: GPL-2.0-or-later > > + */ > > + > > +#ifndef BLOCK_RAM_REGISTRAR_H > > +#define BLOCK_RAM_REGISTRAR_H > > + > > +#include "exec/ramlist.h" > > + > > +/** > > + * struct BlockRAMRegistrar: > > + * > > + * Keeps RAMBlock memory registered with a BlockBackend using > > + * blk_register_buf() including hotplugged memory. > > + * > > + * Emulated devices or other BlockBackend users initialize a > > BlockRAMRegistrar > > + * with blk_ram_registrar_init() before submitting I/O requests with the > > + * BLK_REQ_REGISTERED_BUF flag set. > > s/BLK/BDRV/, right? Thanks, fixed! Stefan
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