block: add BlockRAMRegistrar

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 <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-10-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2022-10-13 14:59:04 -04:00
parent 4fdd0a1a7e
commit 7f9241d805
4 changed files with 97 additions and 0 deletions

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@ -2510,6 +2510,7 @@ 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*

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@ -0,0 +1,58 @@
/*
* BlockBackend RAM Registrar
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "qemu/osdep.h"
#include "sysemu/block-backend.h"
#include "sysemu/block-ram-registrar.h"
#include "qapi/error.h"
static void ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
size_t max_size)
{
BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
Error *err = NULL;
if (!r->ok) {
return; /* don't try again if we've already failed */
}
if (!blk_register_buf(r->blk, host, max_size, &err)) {
error_report_err(err);
ram_block_notifier_remove(&r->notifier);
r->ok = false;
}
}
static void ram_block_removed(RAMBlockNotifier *n, void *host, size_t size,
size_t max_size)
{
BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
blk_unregister_buf(r->blk, host, max_size);
}
void blk_ram_registrar_init(BlockRAMRegistrar *r, BlockBackend *blk)
{
r->blk = blk;
r->notifier = (RAMBlockNotifier){
.ram_block_added = ram_block_added,
.ram_block_removed = ram_block_removed,
/*
* .ram_block_resized() is not necessary because we use the max_size
* value that does not change across resize.
*/
};
r->ok = true;
ram_block_notifier_add(&r->notifier);
}
void blk_ram_registrar_destroy(BlockRAMRegistrar *r)
{
if (r->ok) {
ram_block_notifier_remove(&r->notifier);
}
}

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@ -46,6 +46,7 @@ block_ss.add(files(
), zstd, zlib, gnutls)
softmmu_ss.add(when: 'CONFIG_TCG', if_true: files('blkreplay.c'))
softmmu_ss.add(files('block-ram-registrar.c'))
if get_option('qcow1').allowed()
block_ss.add(files('qcow.c'))

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@ -0,0 +1,37 @@
/*
* 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
* BDRV_REQ_REGISTERED_BUF flag set.
*/
typedef struct {
BlockBackend *blk;
RAMBlockNotifier notifier;
bool ok;
} BlockRAMRegistrar;
void blk_ram_registrar_init(BlockRAMRegistrar *r, BlockBackend *blk);
void blk_ram_registrar_destroy(BlockRAMRegistrar *r);
/* Have all RAMBlocks been registered successfully? */
static inline bool blk_ram_registrar_ok(BlockRAMRegistrar *r)
{
return r->ok;
}
#endif /* BLOCK_RAM_REGISTRAR_H */