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b=hf9bYJ80e8mo7uRTzk9PvAOXk24thjgM3Nx0h4knc6Ejt/QopDc0w/KMYiqTUqdSU NV1Tu4lsemjq1nT95EK5hf9j8btk62yCVgGbOc5EgUh0OYMcpj5nT8S/Eazk4u3qGI 3IHexIj6haCdm0fEUCyTc3grx57THgzuz4aQE6HNINwx/Qp9AB0jZXRC1etuL4kcZu Q+4aijjuRJwTHs0bbQuW69upCf/vnBWzXysURO54rAHDaPSh53SlJyjrjvaKy7oBWY ALI1bhuzqXJ39DO3TOcmZyDw7dN1IKnRQTxGgCu5keCZko/9391eZtqCS8tED/nnjj hO6me+Czimoow== Message-ID: <238ab437-06b1-43ef-86bb-9341c02040b1@kernel.org> Date: Wed, 8 Apr 2026 14:17:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V1 07/16] arm64/mm: Convert READ_ONCE() as p4dp_get() while accessing P4D To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Ryan Roberts , Mark Rutland , Lorenzo Stoakes , Andrew Morton , Mike Rapoport , Linu Cherian , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com References: <20260224051153.3150613-1-anshuman.khandual@arm.com> <20260224051153.3150613-8-anshuman.khandual@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 500F510000F X-Stat-Signature: 4ypoid79jqznaty1we6umgws6ikueast X-Rspam-User: X-HE-Tag: 1775650648-460419 X-HE-Meta: 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 QnwFe6is 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/24/26 06:11, Anshuman Khandual wrote: > Convert all READ_ONCE() based P4D accesses as p4dp_get() instead which will > support both D64 and D128 translation regime going forward. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ryan Roberts > Cc: Mark Rutland > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Cc: kasan-dev@googlegroups.com > Signed-off-by: Anshuman Khandual > --- [...] > static void __init kasan_pgd_populate(unsigned long addr, unsigned long end, > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index a80d06db4de6..16ae11b29f66 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -354,7 +354,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, > { > int ret = 0; > unsigned long next; > - p4d_t p4d = READ_ONCE(*p4dp); > + p4d_t p4d = p4dp_get(p4dp); > pud_t *pudp; > > if (p4d_none(p4d)) { > @@ -443,7 +443,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end, > } > > do { > - p4d_t old_p4d = READ_ONCE(*p4dp); > + p4d_t old_p4d = p4dp_get(p4dp); > > next = p4d_addr_end(addr, end); > > @@ -453,7 +453,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end, > goto out; > > BUG_ON(p4d_val(old_p4d) != 0 && > - p4d_val(old_p4d) != READ_ONCE(p4d_val(*p4dp))); > + p4d_val(old_p4d) != (p4d_val(p4dp_get(p4dp)))); Same here, while at it remove the BUG_ON. (see below) > > phys += next - addr; > } while (p4dp++, addr = next, addr != end); > @@ -1541,7 +1541,7 @@ static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr, > do { > next = p4d_addr_end(addr, end); > p4dp = p4d_offset(pgdp, addr); > - p4d = READ_ONCE(*p4dp); > + p4d = p4dp_get(p4dp); > if (p4d_none(p4d)) > continue; > > @@ -1703,7 +1703,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr, > do { > next = p4d_addr_end(addr, end); > p4dp = p4d_offset(pgdp, addr); > - p4d = READ_ONCE(*p4dp); > + p4d = p4dp_get(p4dp); > if (p4d_none(p4d)) > continue; > > @@ -1724,7 +1724,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr, > */ > p4dp = p4d_offset(pgdp, 0UL); > for (i = 0; i < PTRS_PER_P4D; i++) { > - if (!p4d_none(READ_ONCE(p4dp[i]))) > + if (!p4d_none(p4dp_get(p4dp + i))) > return; > } > > @@ -2258,4 +2258,21 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma, > } > #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */ > > +#if CONFIG_PGTABLE_LEVELS > 3 > +phys_addr_t pud_offset_phys(p4d_t *p4dp, unsigned long addr) > +{ > + p4d_t p4d = p4dp_get(p4dp); > + > + BUG_ON(!pgtable_l4_enabled()); Heh, while at it, convert that to a VM_WARN_ON_ONCE() or anything else that is not a BUG. I strongly assume CONFIG_DEBUG_VM checks are sufficient. > + > + return p4d_page_paddr(p4d) + pud_index(addr) * sizeof(pud_t); > +} > + -- Cheers, David