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b=lhufBt+1XNJzEcjIqIcJ+1N2abIk1ly1qIIe43EMZFBn1onbJT+yEvwkapRDQeGPm YDtFviqqr0u03loYYqQ3lFbBsJyCTb2JQl71Jilnftn1xwZPAR1L+7DMrncNuSBIAa ZLDvpvErdwINXBNW/GavrD9Qv/Eos7oU5SbO7JOsUlZc0r+6ETUIiCznKXqO6yRCd5 S+haPKqdJjpl7ptpbg6xhxN55C7XCZDcyvm6cD47/Z++SOmxVqAbYMQSbNl+FB33w7 wBWAdhVf4W1r9YWJ66jqbZlv1u7v55M6neWNkaIALfw23TgZyp4zEcDkPcyjPWo3wl c6zW3LnrZvwOA== Date: Sun, 2 Aug 2026 19:13:55 +0300 From: Mike Rapoport To: Brendan Jackman Cc: Borislav Petkov , Dave Hansen , Peter Zijlstra , Andrew Morton , David Hildenbrand , Vlastimil Babka , Wei Xu , Johannes Weiner , Zi Yan , Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, Sumit Garg , Will Deacon , rientjes@google.com, "Kalyazin, Nikita" , patrick.roy@linux.dev, "Itazuri, Takahiro" , Andy Lutomirski , David Kaplan , Thomas Gleixner , Yosry Ahmed , Patrick Bellasi , Reiji Watanabe , Sean Christopherson Subject: Re: [PATCH v3 04/26] x86/mm: split out preallocate_sub_pgd() Message-ID: References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com> <20260726-page_alloc-unmapped-v3-4-6f5729aa9832@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260726-page_alloc-unmapped-v3-4-6f5729aa9832@google.com> X-Rspam-User: X-Rspamd-Queue-Id: 4D7268000C X-Rspamd-Server: rspam01 X-Stat-Signature: 5itowef37u4t3wbky5ugo8o864rf1jns X-HE-Tag: 1785687245-700088 X-HE-Meta: U2FsdGVkX18c81wUakuC+QV+4Mj4j+/0g3AjUTfD/8NttH/pTsQ78NMcIp7v0YuHfU+YMBd9kngwXE10j22qpLgWVwCtKCkWcPGcazZnBbgln+kuRn+Pab+70ZGGbKKxMtxyMaY4TSz/EGLHDNHJ9SGK5yWw+GsgfX4/egsYh+RJOfSXr3VTm1N9DCMfENWTiAF3BreU2LNGkMwnrskpZ8xMIIk24FSA6nfQbZ1twyz2btI54K5mHxazJo7NgQEULbd1AwZzFsXFL919pOVB55qb99wLRVnITRorGiB4gbPSCKaGpkia5XOABg0klKdILvkx2vHC1+psMD+tU0pZfmEUmL75BPjfzG1zlaXbBcW9u/sEKdxo9UZ/IPPUwp9sxM5iZUhFio0MDbhSxUQypdprI5OWbw3rwyNzgRC3cKtzElrw712uSkYSupSVlFBYByFBFlXo8D3sZ1gP9p3/tUk3P1wrmEmG2bPAuOVBR/t2OOZEj3DRvQUV2tDwaYj3ALgPrEXaCMtavmX/o7ELojRS5FMW+P6xg+US1SpYhT6fMLPzxh+G8huOHNtG8AOGmr8TWW1y9uXhiLa04fkfn4i+tkLzqKXlB9fEUVemFlSiFYwxRZnNCOMQc7DYwnuBZL7aw805K4VryM4J6iOZQnaDgr5CfhOJI/or2eN2xjy/gxJjx4PrsJLmT17yOOO1Y2O4RBbZUHoTx0w8a0Va0bgKmVYJ8XABDn/PuxRY+AOyh78jCehlat2PYx2/Wsz7YbwO9l37nTEgviC58jdJqOR9xEvApWEwLyFkTrpexfxtjEV7DPO49qJYJ+ZPrh+nZBFLzDvn0hbNEAWCMiZ2SruPwL1/cPBtLUsw+6um3fp/Euk559xh9Apxh7SOnBOnDmIT4A/R+4Dyw+XovKPMOTr9xgRUqR2f4ZOVT2VWbUJyKE2q27wOLl84kcjaK63riBTYrU8cxcJYgjZZlx2 8Gw+TW8f XEj+z93OI3C9WbMmoCMxlqmnP6OOQqRjJWHXqV9kv3w5utothA2v6wYekMcu/SICZkZ0JXn93pVQvmXh3UWlCpAJVp1dO9fLIJ5XPFOPLz+vfr5zg9BoOWX2ObALibsmsf9IFeC2qKiuEnrZwW01V9o17ToIeFVv//6oDpexzdO3Cs+HeRWSBJb/pGGZOao/nGELRHcul3LcH6u9VFeP9CbJ8Z+CalX7IG4KIRB/lk93SLnD06rbcQEacXSEIYu6hxFhfrDXKCpc3XufcVpyRo6sgiP17YHSTe4ItvuyiR6La0IamV9kN7vXU4m6l0DVO6BO985Nhqo+oZfOyIpiS8wWjIYmMyYbGfh3tA6os3DaVwpk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Jul 26, 2026 at 10:22:37PM +0000, Brendan Jackman wrote: > This code will be needed elsewhere in a following patch. Split out the > trivial code move for easy review. > > As a side effect, change the logging slightly: instead of directly > reporting the level of the failure in panic(), show a generic panic > message, will be preceded by a separate warn that reports the level of > the failure. This is a simple way to have this helper suit the needs of > its new user as well as the existing one. > > Other than logging, no functional change intended. > > Signed-off-by: Brendan Jackman > --- > arch/x86/include/asm/pgalloc.h | 3 +++ > arch/x86/mm/init_64.c | 44 +++++++----------------------------------- > arch/x86/mm/pgtable.c | 38 ++++++++++++++++++++++++++++++++++++ > 3 files changed, 48 insertions(+), 37 deletions(-) > > diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h > index c88691b15f3c6..2aba6cfabf495 100644 > --- a/arch/x86/include/asm/pgalloc.h > +++ b/arch/x86/include/asm/pgalloc.h > @@ -2,6 +2,7 @@ > #ifndef _ASM_X86_PGALLOC_H > #define _ASM_X86_PGALLOC_H > > +#include I think this should go to arch/x86/mm/pgtable.c. pgalloc.h does not need printk symbols. > #include > #include /* for struct page */ > #include > @@ -128,6 +129,8 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud, > ___pud_free_tlb(tlb, pud); > } > > +extern int preallocate_sub_pgd(struct mm_struct *mm, unsigned long addr); > + > #if CONFIG_PGTABLE_LEVELS > 4 > static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, p4d_t *p4d) > { > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index ab4c5a02326f7..ac6688c70872e 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -1293,46 +1293,16 @@ static struct kcore_list kcore_vsyscall; > static void __init preallocate_vmalloc_pages(void) > { > unsigned long addr; > - const char *lvl; > > for (addr = VMALLOC_START; addr <= VMEMORY_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) { > - pgd_t *pgd = pgd_offset_k(addr); > - p4d_t *p4d; > - pud_t *pud; > - > - lvl = "p4d"; > - p4d = p4d_alloc(&init_mm, pgd, addr); > - if (!p4d) > - goto failed; > - > - if (pgtable_l5_enabled()) > - continue; > - > - /* > - * The goal here is to allocate all possibly required > - * hardware page tables pointed to by the top hardware > - * level. > - * > - * On 4-level systems, the P4D layer is folded away and > - * the above code does no preallocation. Below, go down > - * to the pud _software_ level to ensure the second > - * hardware level is allocated on 4-level systems too. > - */ > - lvl = "pud"; > - pud = pud_alloc(&init_mm, p4d, addr); > - if (!pud) > - goto failed; > + if (preallocate_sub_pgd(&init_mm, addr)) { > + /* > + * The pages have to be there now or they will be > + * missing in process page-tables later. > + */ > + panic("Failed to pre-allocate pagetables for vmalloc area\n"); > + } > } > - > - return; > - > -failed: > - > - /* > - * The pages have to be there now or they will be missing in > - * process page-tables later. > - */ > - panic("Failed to pre-allocate %s pages for vmalloc area\n", lvl); > } > > void __init arch_mm_preinit(void) > diff --git a/arch/x86/mm/pgtable.c b/ > index f32facdb30354..fdd3709509946 100644 > --- a/arch/x86/mm/pgtable.c > +++ b/arch/x86/mm/pgtable.c > @@ -833,3 +833,41 @@ void arch_check_zapped_pud(struct vm_area_struct *vma, pud_t pud) > /* See note in arch_check_zapped_pte() */ > VM_WARN_ON_ONCE(!(vma->vm_flags & VM_SHADOW_STACK) && pud_shstk(pud)); > } > + > +#if CONFIG_PGTABLE_LEVELS > 3 > +/* > + * Allocate all possibly required hardware page tables pointed to ths > + * top hardware level. In other words, allocate a p4d on 5-level or a > + * pud on 4-level. > + */ > +int preallocate_sub_pgd(struct mm_struct *mm, unsigned long addr) > +{ > + const char *lvl; > + p4d_t *p4d; > + pud_t *pud; > + > + lvl = "p4d"; > + p4d = p4d_alloc(mm, pgd_offset_pgd(mm->pgd, addr), addr); > + if (!p4d) > + goto failed; > + > + if (pgtable_l5_enabled()) > + return 0; > + > + /* > + * On 4-level systems, the P4D layer is folded away and > + * the above code does no preallocation. Below, go down > + * to the pud _software_ level to ensure the second > + * hardware level is allocated on 4-level systems too. > + */ > + lvl = "pud"; > + pud = pud_alloc(mm, p4d, addr); > + if (!pud) > + goto failed; > + return 0; > + > +failed: > + pr_warn_ratelimited("Failed to preallocate %s\n", lvl); > + return -ENOMEM; > +} > +#endif > > -- > 2.54.0 > -- Sincerely yours, Mike.