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Tue, 25 Feb 2025 08:36:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id xlNQGh6BvWemAwAAD6G6ig (envelope-from ); Tue, 25 Feb 2025 08:36:46 +0000 Date: Tue, 25 Feb 2025 09:36:44 +0100 From: Oscar Salvador To: Dave Hansen Cc: Gwan-gyeong Mun , linux-kernel@vger.kernel.org, 42.hyeyoo@gmail.com, byungchul@sk.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, stable@vger.kernel.org, linux-mm@kvack.org, max.byungchul.park@sk.com, max.byungchul.park@gmail.com Subject: Re: [PATCH] x86/vmemmap: Synchronize with global pgds if populating init_mm's pgd Message-ID: References: <20250220064105.808339-1-gwan-gyeong.mun@intel.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 3E4572118E X-Spam-Level: X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[13]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[intel.com,vger.kernel.org,gmail.com,sk.com,linux.intel.com,kernel.org,infradead.org,linux-foundation.org,kvack.org]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TAGGED_RCPT(0.00)[]; ASN(0.00)[asn:25478, ipnet:::/0, country:RU]; RCVD_VIA_SMTP_AUTH(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; MISSING_XM_UA(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:dkim,localhost.localdomain:mid] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Score: -3.01 X-Spam-Flag: NO On Thu, Feb 20, 2025 at 10:02:54AM -0800, Dave Hansen wrote: > On 2/19/25 22:41, Gwan-gyeong Mun wrote: > > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > > index 01ea7c6df303..7935859bcc21 100644 > > --- a/arch/x86/mm/init_64.c > > +++ b/arch/x86/mm/init_64.c > > @@ -1498,6 +1498,54 @@ static long __meminitdata addr_start, addr_end; > > static void __meminitdata *p_start, *p_end; > > static int __meminitdata node_start; > > > > +static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node) > > +{ > > + void *p = vmemmap_alloc_block(size, node); > > + > > + if (!p) > > + return NULL; > > + memset(p, 0, size); > > + > > + return p; > > +} > > This is a pure copy and paste of the generic function. I assume this is > because the mm/sparse-vmemmap.c is static. But this kind of copying is > really unfortunate. Agreed. > ... > > +pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node) > > +{ > > + pgd_t *pgd = pgd_offset_k(addr); > > + > > + if (pgd_none(*pgd)) { > > + void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); > > + > > + if (!p) > > + return NULL; > > + > > + pgd_populate(&init_mm, pgd, p); > > + sync_global_pgds(addr, addr); > > + } > > + > > + return pgd; > > +} > > I'd _really_ like to find another way to do this. We really don't want > to add copy-and-paste versions of generic functions that we now need to > maintain on the x86 side. > > The _best_ way is probably to create some p*d_populate_kernel() helpers: > > void pgd_populate_kernel(unsigned long addr, pgd_t *pgd, p4d_t *p4d) > { > pgd_populate(&init_mm, pgd, p4d); > arch_sync_global_pgds(addr, addr+something); > } > > and move over most of the callers of: > > p*d_populate(&init_mm, ...); I think this makes more sense, yes. So for those that do not need the sync, arch_sync_* would be just a noop, so we could avoid all these code duplication. -- Oscar Salvador SUSE Labs