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b=FYMEDT0vkpzQD1yVnU2etV+jk/xcPPcRTnjJp1dXIe/kvA6wjKMmb83lmvnh8j5Dn FwLVn5mOCLtsTAdqA8e9IKWDT8E1G/31jkuFdgTQUCFVqcwxZht7KJGKevoP0JH57J zIBXGFM5s+eE2aQNps/yAwPufE7fmtUFgh5S+pdLnqdIwIE0yH8pddlodbrR/Hh68c J+fx3cQBjp5VlcuCQVssVUXpZBD4CM8gk4ClcVRitd++N7JJMo/HaUn7xM2sRhbxoc Y6npf+jqNIb0LcL/u5Ot+hkLv2CRV/M1fhsdaJAuwPjh2aZYzFqDbdqvwGc5WIeaJ4 ZKaBEjhF8DWgw== From: =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= To: David Hildenbrand , Alexandre Ghiti , Albert Ou , Palmer Dabbelt , Paul Walmsley , linux-riscv@lists.infradead.org Cc: =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Andrew Bresticker , Chethan Seshadri , Lorenzo Stoakes , Oscar Salvador , Santosh Mamila , Sivakumar Munnangi , Sunil V L , linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v2 4/8] riscv: mm: Add memory hotplugging support In-Reply-To: <267be75e-ed4a-45d0-883f-51c7324c30f1@redhat.com> References: <20240514140446.538622-1-bjorn@kernel.org> <20240514140446.538622-5-bjorn@kernel.org> <267be75e-ed4a-45d0-883f-51c7324c30f1@redhat.com> Date: Tue, 14 May 2024 18:34:46 +0200 Message-ID: <87r0e4tkrd.fsf@all.your.base.are.belong.to.us> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: f61aics8edswqrnjt8ctbbjqhr6dbhfp X-Rspamd-Queue-Id: 1EAF01A0023 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1715704493-235212 X-HE-Meta: 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 zMR+U4O9 26n8vySs1maL/+9mS8zrYaZLY4SqgqJkLpjQNwfWzg9bxHax1NiAwrW7wiKYh/4uk63QBvaZhH56srBT0RzuZe7sA5tk8FSXrD3kkn7mJkeXxKp3Oybjyk4mPIBhPlbYVlExtlZkkamiPIZ2fyHWkCNqVKJePOhCcH7RiQSTeaAOoqiQPr0fR8056rFMHAgVb/7LGA+dwOKA61qf5KeaAsDOD1dq5z8Gd7pV10kwGhwzZlGIEF0W40R12v2eXbFdWFInSOr0WX8VcMnc0iv1/UGt7LE59ENu7cScETRXFTI1vqV+rYKxqv4ozdQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: David Hildenbrand writes: > On 14.05.24 16:04, Bj=C3=B6rn T=C3=B6pel wrote: >> From: Bj=C3=B6rn T=C3=B6pel >>=20 >> For an architecture to support memory hotplugging, a couple of >> callbacks needs to be implemented: >>=20 >> arch_add_memory() >> This callback is responsible for adding the physical memory into the >> direct map, and call into the memory hotplugging generic code via >> __add_pages() that adds the corresponding struct page entries, and >> updates the vmemmap mapping. >>=20 >> arch_remove_memory() >> This is the inverse of the callback above. >>=20 >> vmemmap_free() >> This function tears down the vmemmap mappings (if >> CONFIG_SPARSEMEM_VMEMMAP is enabled), and also deallocates the >> backing vmemmap pages. Note that for persistent memory, an >> alternative allocator for the backing pages can be used; The >> vmem_altmap. This means that when the backing pages are cleared, >> extra care is needed so that the correct deallocation method is >> used. >>=20 >> arch_get_mappable_range() >> This functions returns the PA range that the direct map can map. >> Used by the MHP internals for sanity checks. >>=20 >> The page table unmap/teardown functions are heavily based on code from >> the x86 tree. The same remove_pgd_mapping() function is used in both >> vmemmap_free() and arch_remove_memory(), but in the latter function >> the backing pages are not removed. >>=20 >> Signed-off-by: Bj=C3=B6rn T=C3=B6pel >> --- >> arch/riscv/mm/init.c | 242 +++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 242 insertions(+) >>=20 >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> index 6f72b0b2b854..7f0b921a3d3a 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -1493,3 +1493,245 @@ void __init pgtable_cache_init(void) >> } >> } >> #endif >> + >> +#ifdef CONFIG_MEMORY_HOTPLUG >> +static void __meminit free_pte_table(pte_t *pte_start, pmd_t *pmd) >> +{ >> + pte_t *pte; >> + int i; >> + >> + for (i =3D 0; i < PTRS_PER_PTE; i++) { >> + pte =3D pte_start + i; >> + if (!pte_none(*pte)) >> + return; >> + } >> + >> + free_pages((unsigned long)page_address(pmd_page(*pmd)), 0); >> + pmd_clear(pmd); >> +} >> + >> +static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud) >> +{ >> + pmd_t *pmd; >> + int i; >> + >> + for (i =3D 0; i < PTRS_PER_PMD; i++) { >> + pmd =3D pmd_start + i; >> + if (!pmd_none(*pmd)) >> + return; >> + } >> + >> + free_pages((unsigned long)page_address(pud_page(*pud)), 0); >> + pud_clear(pud); >> +} >> + >> +static void __meminit free_pud_table(pud_t *pud_start, p4d_t *p4d) >> +{ >> + pud_t *pud; >> + int i; >> + >> + for (i =3D 0; i < PTRS_PER_PUD; i++) { >> + pud =3D pud_start + i; >> + if (!pud_none(*pud)) >> + return; >> + } >> + >> + free_pages((unsigned long)page_address(p4d_page(*p4d)), 0); >> + p4d_clear(p4d); >> +} >> + >> +static void __meminit free_vmemmap_storage(struct page *page, size_t si= ze, >> + struct vmem_altmap *altmap) >> +{ >> + if (altmap) >> + vmem_altmap_free(altmap, size >> PAGE_SHIFT); >> + else >> + free_pages((unsigned long)page_address(page), get_order(size)); > > If you unplug a DIMM that was added during boot (can happen on x86-64,=20 > can it happen on riscv?), free_pages() would not be sufficient. You'd be= =20 > freeing a PG_reserved page that has to be freed differently. I'd say if it can happen on x86-64, it probably can on RISC-V. I'll look into this for the next spin! Thanks for spending time on the series! Cheers, Bj=C3=B6rn