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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 In-Reply-To: References: <20241206005834.1050905-1-peterx@redhat.com> <20241206005834.1050905-4-peterx@redhat.com> <874j3hc4fw.fsf@suse.de> Date: Fri, 06 Dec 2024 12:10:46 -0300 Message-ID: <87ldwsc0eh.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[7]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo, suse.de:mid, suse.de:email] Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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 Peter Xu writes: > 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! ^^^^ Ah, so RAM_SAVE_FLAG_FULL was left behind but RAM_SAVE_FLAG_COMPRESS_PAGE was removed, I missed that. > >> >> > +#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? Yes, please. > >> >> >> > + >> > 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 >>