> -----Original Message-----
> From: Fabiano Rosas <faro...@suse.de>
> Sent: Saturday, January 6, 2024 4:07 AM
> To: Bryan Zhang <bryan.zh...@bytedance.com>; qemu-devel@nongnu.org;
> marcandre.lur...@redhat.com; pet...@redhat.com; quint...@redhat.com;
> peter.mayd...@linaro.org; hao.xi...@bytedance.com
> Cc: bryan.zh...@bytedance.com; Liu, Yuan1 <yuan1....@intel.com>;
> berra...@redhat.com
> Subject: Re: [PATCH 3/5] migration: Introduce unimplemented 'qatzip'
> compression method
>
> Bryan Zhang <bryan.zh...@bytedance.com> writes:
>
> +cc Yuan Liu, Daniel Berrangé
>
> > Adds support for 'qatzip' as an option for the multifd compression
> > method parameter, but copy-pastes the no-op logic to leave the actual
> > methods effectively unimplemented. This is in preparation of a
> > subsequent commit that will implement actually using QAT for
> > compression and decompression.
> >
> > Signed-off-by: Bryan Zhang <bryan.zh...@bytedance.com>
> > Signed-off-by: Hao Xiang <hao.xi...@bytedance.com>
> > ---
> > hw/core/qdev-properties-system.c | 6 ++-
> > migration/meson.build | 1 +
> > migration/multifd-qatzip.c | 81 ++++++++++++++++++++++++++++++++
> > migration/multifd.h | 1 +
> > qapi/migration.json | 5 +-
> > 5 files changed, 92 insertions(+), 2 deletions(-) create mode 100644
> > migration/multifd-qatzip.c
> >
> > diff --git a/hw/core/qdev-properties-system.c
> > b/hw/core/qdev-properties-system.c
> > index 1a396521d5..d8e48dcb0e 100644
> > --- a/hw/core/qdev-properties-system.c
> > +++ b/hw/core/qdev-properties-system.c
> > @@ -658,7 +658,11 @@ const PropertyInfo qdev_prop_fdc_drive_type = {
> > const PropertyInfo qdev_prop_multifd_compression = {
> > .name = "MultiFDCompression",
> > .description = "multifd_compression values, "
> > - "none/zlib/zstd",
> > + "none/zlib/zstd"
> > +#ifdef CONFIG_QATZIP
> > + "/qatzip"
> > +#endif
> > + ,
> > .enum_table = &MultiFDCompression_lookup,
> > .get = qdev_propinfo_get_enum,
> > .set = qdev_propinfo_set_enum,
> > diff --git a/migration/meson.build b/migration/meson.build index
> > 92b1cc4297..e20f318379 100644
> > --- a/migration/meson.build
> > +++ b/migration/meson.build
> > @@ -40,6 +40,7 @@ if get_option('live_block_migration').allowed()
> > system_ss.add(files('block.c'))
> > endif
> > system_ss.add(when: zstd, if_true: files('multifd-zstd.c'))
> > +system_ss.add(when: qatzip, if_true: files('multifd-qatzip.c'))
> >
> > specific_ss.add(when: 'CONFIG_SYSTEM_ONLY',
> > if_true: files('ram.c', diff --git
> > a/migration/multifd-qatzip.c b/migration/multifd-qatzip.c new file
> > mode 100644 index 0000000000..1733bbddb7
> > --- /dev/null
> > +++ b/migration/multifd-qatzip.c
> > @@ -0,0 +1,81 @@
> > +/*
> > + * Multifd QATzip compression implementation
> > + *
> > + * Copyright (c) Bytedance
> > + *
> > + * Authors:
> > + * Bryan Zhang <bryan.zh...@bytedance.com>
> > + * Hao Xiang <hao.xi...@bytedance.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or
> later.
> > + * See the COPYING file in the top-level directory.
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "exec/ramblock.h"
> > +#include "exec/target_page.h"
> > +#include "qapi/error.h"
> > +#include "migration.h"
> > +#include "options.h"
> > +#include "multifd.h"
> > +
> > +static int qatzip_send_setup(MultiFDSendParams *p, Error **errp) {
> > + return 0;
> > +}
> > +
> > +static void qatzip_send_cleanup(MultiFDSendParams *p, Error **errp)
> > +{};
> > +
> > +static int qatzip_send_prepare(MultiFDSendParams *p, Error **errp) {
> > + MultiFDPages_t *pages = p->pages;
> > +
> > + for (int i = 0; i < p->normal_num; i++) {
> > + p->iov[p->iovs_num].iov_base = pages->block->host + p-
> >normal[i];
> > + p->iov[p->iovs_num].iov_len = p->page_size;
> > + p->iovs_num++;
> > + }
> > +
> > + p->next_packet_size = p->normal_num * p->page_size;
> > + p->flags |= MULTIFD_FLAG_NOCOMP;
> > + return 0;
> > +}
> > +
> > +static int qatzip_recv_setup(MultiFDRecvParams *p, Error **errp) {
> > + return 0;
> > +}
> > +
> > +static void qatzip_recv_cleanup(MultiFDRecvParams *p) {};
> > +
> > +static int qatzip_recv_pages(MultiFDRecvParams *p, Error **errp) {
> > + uint32_t flags = p->flags & MULTIFD_FLAG_COMPRESSION_MASK;
> > +
> > + if (flags != MULTIFD_FLAG_NOCOMP) {
> > + error_setg(errp, "multifd %u: flags received %x flags
> expected %x",
> > + p->id, flags, MULTIFD_FLAG_NOCOMP);
> > + return -1;
> > + }
> > + for (int i = 0; i < p->normal_num; i++) {
> > + p->iov[i].iov_base = p->host + p->normal[i];
> > + p->iov[i].iov_len = p->page_size;
> > + }
> > + return qio_channel_readv_all(p->c, p->iov, p->normal_num, errp);
> > +}
> > +
> > +static MultiFDMethods multifd_qatzip_ops = {
> > + .send_setup = qatzip_send_setup,
> > + .send_cleanup = qatzip_send_cleanup,
> > + .send_prepare = qatzip_send_prepare,
> > + .recv_setup = qatzip_recv_setup,
> > + .recv_cleanup = qatzip_recv_cleanup,
> > + .recv_pages = qatzip_recv_pages
> > +};
> > +
> > +static void multifd_qatzip_register(void) {
> > + multifd_register_ops(MULTIFD_COMPRESSION_QATZIP,
> > +&multifd_qatzip_ops); }
> > +
> > +migration_init(multifd_qatzip_register);
> > diff --git a/migration/multifd.h b/migration/multifd.h index
> > a835643b48..5600f7fc82 100644
> > --- a/migration/multifd.h
> > +++ b/migration/multifd.h
> > @@ -33,6 +33,7 @@ int multifd_queue_page(QEMUFile *f, RAMBlock *block,
> > ram_addr_t offset); #define MULTIFD_FLAG_NOCOMP (0 << 1) #define
> > MULTIFD_FLAG_ZLIB (1 << 1) #define MULTIFD_FLAG_ZSTD (2 << 1)
> > +#define MULTIFD_FLAG_QATZIP (3 << 1)
> >
> > /* This value needs to be a multiple of qemu_target_page_size() */
> > #define MULTIFD_PACKET_SIZE (512 * 1024) diff --git
> > a/qapi/migration.json b/qapi/migration.json index
> > 6d5a4b0489..e3cc195aed 100644
> > --- a/qapi/migration.json
> > +++ b/qapi/migration.json
> > @@ -625,11 +625,14 @@
> > #
> > # @zstd: use zstd compression method.
> > #
> > +# @qatzip: use qatzip compression method.
> > +#
> > # Since: 5.0
> > ##
> > { 'enum': 'MultiFDCompression',
> > 'data': [ 'none', 'zlib',
> > - { 'name': 'zstd', 'if': 'CONFIG_ZSTD' } ] }
> > + { 'name': 'zstd', 'if': 'CONFIG_ZSTD' },
> > + { 'name': 'qatzip', 'if': 'CONFIG_QATZIP'} ] }
>
> In another thread adding support to another Intel accelerator (IAA) we
> decided that it was better to select the offloading as an accelerator
> method to multifd zlib rather than as an entirely new compression format.
> Take a look at that discussion:
> https://lore.kernel.org/r/ztfcnqbbqlmsu...@redhat.com
>
> As I understand it, QAT + QATzip would be compatible with both zlib and
> IAA + QPL, so we'd add another accelerator method like this:
>
> https://lore.kernel.org/r/20240103112851.908082-3-yuan1....@intel.com
>
> All that, of course, assuming we even want to support both accelerators.
> They're addressing the same problem after all. I wonder how we'd choose a
> precedence, since both seem to be present in the same processor family.
I agree that IAA and QAT should run under the accelerator framework and be
compatible with zlib.
Regarding the choice between QAT and IAA:
1. This decision can be determined by the end customer through live migration
parameters. The Xeon products have different specifications, which will impact
the presence and quantity of IAA and QAT devices.
2. If the customer's chosen product includes both IAA and QAT, the live
migration
software can list the priority of accelerators supporting the zlib compression
algorithm.
