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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d8da6b651asm19738816d6.69.2024.12.06.07.03.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Dec 2024 07:03:08 -0800 (PST) Date: Fri, 6 Dec 2024 10:03:06 -0500 From: Peter Xu To: Fabiano Rosas Cc: qemu-devel@nongnu.org, "Maciej S . Szmigiero" , =?utf-8?Q?C=C3=A9dric?= Le Goater , Avihai Horon , Alex Williamson , Prasad Pandit Subject: Re: [PATCH v2 3/7] migration/ram: Move RAM_SAVE_FLAG* into ram.h Message-ID: References: <20241206005834.1050905-1-peterx@redhat.com> <20241206005834.1050905-4-peterx@redhat.com> <874j3hc4fw.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <874j3hc4fw.fsf@suse.de> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.996, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Dec 06, 2024 at 10:43:31AM -0300, Fabiano Rosas wrote: > Peter Xu writes: > > > Firstly, we're going to use the multifd flag soon in multifd code, so ram.c > > isn't gonna work. > > > > Secondly, we have a separate RDMA flag dangling around, which is definitely > > not obvious. There's one comment that helps, but not too much. > > > > We should just put it altogether, so nothing will get overlooked. > > > > Signed-off-by: Peter Xu > > Reviewed-by: Fabiano Rosas > > just some comments about preexisting stuff: > > > --- > > migration/ram.h | 25 +++++++++++++++++++++++++ > > migration/rdma.h | 7 ------- > > migration/ram.c | 21 --------------------- > > 3 files changed, 25 insertions(+), 28 deletions(-) > > > > diff --git a/migration/ram.h b/migration/ram.h > > index 0d1981f888..cfdcccd266 100644 > > --- a/migration/ram.h > > +++ b/migration/ram.h > > @@ -33,6 +33,31 @@ > > #include "exec/cpu-common.h" > > #include "io/channel.h" > > > > +/* > > + * RAM_SAVE_FLAG_ZERO used to be named RAM_SAVE_FLAG_COMPRESS, it > > + * worked for pages that were filled with the same char. We switched > > + * it to only search for the zero value. And to avoid confusion with > > + * RAM_SAVE_FLAG_COMPRESS_PAGE just rename it. > > + * > > + * RAM_SAVE_FLAG_FULL was obsoleted in 2009. > > + * > > + * RAM_SAVE_FLAG_COMPRESS_PAGE (0x100) was removed in QEMU 9.1. > > Aren't these already covered by git log? The comment makes it seem like > some special situation, but I think we're just documenting history here, > no? I guess so. Maybe still useful when we hit a bug that some ancient QEMU manually migrates to a new one and hit a weird 0x100 message. > > > + */ > > +#define RAM_SAVE_FLAG_FULL 0x01 > > +#define RAM_SAVE_FLAG_ZERO 0x02 > > +#define RAM_SAVE_FLAG_MEM_SIZE 0x04 > > +#define RAM_SAVE_FLAG_PAGE 0x08 > > +#define RAM_SAVE_FLAG_EOS 0x10 > > +#define RAM_SAVE_FLAG_CONTINUE 0x20 > > +#define RAM_SAVE_FLAG_XBZRLE 0x40 > > +/* > > + * ONLY USED IN RDMA: Whenever this is found in the data stream, the flags > > + * will be passed to rdma functions in the incoming-migration side. > > + */ > > +#define RAM_SAVE_FLAG_HOOK 0x80 > > No 0x100? You just asked about it one min ago! ^^^^ > > > +#define RAM_SAVE_FLAG_MULTIFD_FLUSH 0x200 > > +/* We can't use any flag that is bigger than 0x200 */ > > Where does that limitation come from again? I know that > RAM_SAVE_FLAG_MEM_SIZE shares a u64 with something else: > > qemu_put_be64(f, ram_bytes_total_with_ignored() | > RAM_SAVE_FLAG_MEM_SIZE); > > For RAM_SAVE_FLAG_ZERO and RAM_SAVE_FLAG_PAGE, it might be a u32 (offset > is ram_addr_t): > > save_page_header(pss, file, pss->block, offset | RAM_SAVE_FLAG_ZERO); > > But others just go by themselves: > > qemu_put_be64(f, RAM_SAVE_FLAG_MULTIFD_FLUSH); No matter if it goes by itself, I am guessing migration was initially developed by assuming each initial 8 bytes is an address, see: ram_load_precopy(): addr = qemu_get_be64(f); ... flags = addr & ~TARGET_PAGE_MASK; addr &= TARGET_PAGE_MASK; So it must be no more than 0x200, probably because it wants to work with whatever architectures that have PAGE_SIZE>=1K (which is 0x400). Then the offset will never use the last 10 bits. Wanna me to add a comment for that in this patch? > > > > + > > extern XBZRLECacheStats xbzrle_counters; > > > > /* Should be holding either ram_list.mutex, or the RCU lock. */ > > diff --git a/migration/rdma.h b/migration/rdma.h > > index a8d27f33b8..f55f28bbed 100644 > > --- a/migration/rdma.h > > +++ b/migration/rdma.h > > @@ -33,13 +33,6 @@ void rdma_start_incoming_migration(InetSocketAddress *host_port, Error **errp); > > #define RAM_CONTROL_ROUND 1 > > #define RAM_CONTROL_FINISH 3 > > > > -/* > > - * Whenever this is found in the data stream, the flags > > - * will be passed to rdma functions in the incoming-migration > > - * side. > > - */ > > -#define RAM_SAVE_FLAG_HOOK 0x80 > > - > > #define RAM_SAVE_CONTROL_NOT_SUPP -1000 > > #define RAM_SAVE_CONTROL_DELAYED -2000 > > > > diff --git a/migration/ram.c b/migration/ram.c > > index 7284c34bd8..44010ff325 100644 > > --- a/migration/ram.c > > +++ b/migration/ram.c > > @@ -71,27 +71,6 @@ > > /***********************************************************/ > > /* ram save/restore */ > > > > -/* > > - * RAM_SAVE_FLAG_ZERO used to be named RAM_SAVE_FLAG_COMPRESS, it > > - * worked for pages that were filled with the same char. We switched > > - * it to only search for the zero value. And to avoid confusion with > > - * RAM_SAVE_FLAG_COMPRESS_PAGE just rename it. > > - * > > - * RAM_SAVE_FLAG_FULL was obsoleted in 2009. > > - * > > - * RAM_SAVE_FLAG_COMPRESS_PAGE (0x100) was removed in QEMU 9.1. > > - */ > > -#define RAM_SAVE_FLAG_FULL 0x01 > > -#define RAM_SAVE_FLAG_ZERO 0x02 > > -#define RAM_SAVE_FLAG_MEM_SIZE 0x04 > > -#define RAM_SAVE_FLAG_PAGE 0x08 > > -#define RAM_SAVE_FLAG_EOS 0x10 > > -#define RAM_SAVE_FLAG_CONTINUE 0x20 > > -#define RAM_SAVE_FLAG_XBZRLE 0x40 > > -/* 0x80 is reserved in rdma.h for RAM_SAVE_FLAG_HOOK */ > > -#define RAM_SAVE_FLAG_MULTIFD_FLUSH 0x200 > > -/* We can't use any flag that is bigger than 0x200 */ > > - > > /* > > * mapped-ram migration supports O_DIRECT, so we need to make sure the > > * userspace buffer, the IO operation size and the file offset are > -- Peter Xu