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b=UOQ+l3C3lLujBRXFNmIZbndVsdbScZNJL6O1tqSdqMjmQrjL6ZYziJuWgml1fG0Sf YZjhOpebC9esQLeWBd/jXa9dy1aBOGM9VUfFMdkM1pq8Z2PBJM6ySVz5xzTC6IWHcr hUPG4TiNf0iGjXu2vtdIdxNSmSj85hQyuGO+G/8KJIYORUlSuKuQuG/X9RChqR/x9Y DsHFniEg6Ij/QnQKTcdYooZxqdcI9V1/aRc3LxVfuVuJOyhGvQIWOkfgrAxuFPAZe2 vs5e1PdKfZ70Pm/jfgXnCkSDYJMr9D6/FyFbnT3DbR7iuUbU7GjmYCz5kkL2F0VMoz puMLclabJJmcQ== Date: Sun, 6 Sep 2026 22:33:11 +0300 From: Mike Rapoport To: Vincent Donnefort Cc: catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, sudeep.holla@kernel.org, jenswi@kernel.org, robh@kernel.org, mark.rutland@arm.com, sumit.garg@kernel.org, ardb@kernel.org, thierry.reding@kernel.org, david@kernel.org, danielmentz@google.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, op-tee@lists.trustedfirmware.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 01/10] memblock: Introduce MEMBLOCK_LLMAP Message-ID: References: <20260902104712.2399797-1-vdonnefort@google.com> <20260902104712.2399797-2-vdonnefort@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260902104712.2399797-2-vdonnefort@google.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CD81C16000B X-Stat-Signature: yqqnx93szga65u5skac4qqdpiwxw8mc6 X-Rspam-User: X-HE-Tag: 1788723201-993157 X-HE-Meta: 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 REC3infh YwbG+qN3flIX+aWYUTUqse9Gp212TJCcrv7bFILnitHM0rWcqdCXmTAIu2QKM/stNRoB03H3GUuewG5tl7l40ilGdH0PStFVNpxFjsAwSEKiqir53wSsW/fhbaaP28BU1fjhKSSVsT9GDIJJW9FHi0f7rmX5+m7TM3ZIr477dmJLAWSjuyHy769pzwwjEAZsjDHQlw+9AUwoRhwbsMcz4sO4ZKmnzglpku7egNDPpgf0uegH0LKd2N2Go7nbqwRM3DRiu6RVhJ1E1XaFCUtSxUyFktpwhgzCSQY+UPKt/3TOt4vZbj0cNtQrZgSjFInMfGCNOqBW1fNlPCnM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 02, 2026 at 11:47:03AM +0100, Vincent Donnefort wrote: > Keeping last-level mappings is interesting on some architectures as it > allows mapping/unmapping pages from the kernel direct map without the > risk of splitting blocks which, under the break-before-make rule, may > trigger page-faults the kernel can't handle. > > However, mapping the entire direct map at PTE-level is costly. So > instead, create a new memblock flag MEMBLOCK_LLMAP to enable the system I believe MEMBLOCK_PTE_MAP sounds more descriptive. > to decide which region must be covered by mappings up to the last-level. > > Signed-off-by: Vincent Donnefort > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index d62db9e776cf..d40a5ded188d 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -52,6 +52,7 @@ extern unsigned long long max_possible_pfn; > * kernel that we know is good to use. It is the only memory that > * allocations may happen from in this phase. > * @MEMBLOCK_RSRV_HUGETLB: memory is reserved for hugetlb pages > + * @MEMBLOCK_LLMAP: memory region to be mapped using last-level mapping > */ > enum memblock_flags { > MEMBLOCK_NONE = 0x0, /* No special request */ > @@ -63,6 +64,7 @@ enum memblock_flags { > MEMBLOCK_RSRV_KERN = 0x20, /* memory reserved for kernel use */ > MEMBLOCK_KHO_SCRATCH = 0x40, /* scratch memory for kexec handover */ > MEMBLOCK_RSRV_HUGETLB = 0x80, /* memory reserved for hugetlb pages */ > + MEMBLOCK_LLMAP = 0x100,/* last-level mapping */ > }; > > /** > @@ -160,6 +162,8 @@ int memblock_reserved_mark_noinit(phys_addr_t base, phys_addr_t size); > int memblock_reserved_mark_kern(phys_addr_t base, phys_addr_t size); > int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size); > int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size); > +int memblock_mark_llmap(phys_addr_t base, phys_addr_t size); > +int memblock_clear_llmap(phys_addr_t base, phys_addr_t size); > > void memblock_free(void *ptr, size_t size); > void reset_all_zones_managed_pages(void); > @@ -306,6 +310,11 @@ static inline bool memblock_is_kho_scratch(struct memblock_region *m) > return m->flags & MEMBLOCK_KHO_SCRATCH; > } > > +static inline bool memblock_is_llmap(struct memblock_region *m) > +{ > + return m->flags & MEMBLOCK_LLMAP; > +} > + > int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn, > unsigned long *end_pfn); > void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn, > diff --git a/mm/memblock.c b/mm/memblock.c > index 9ce86349a29f..1591b50503ed 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1119,6 +1119,16 @@ int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size) > */ > int __init_memblock memblock_mark_nomap(phys_addr_t base, phys_addr_t size) > { > + struct memblock_region *r; > + > + memblock_cap_size(base, &size); > + > + for_each_mem_region(r) { > + if (memblock_is_llmap(r) && > + memblock_addrs_overlap(base, size, r->base, r->size)) > + return -EINVAL; > + } I'm not very fond of implicit skips here. memblock has no idea what's the caller intention, maybe it actually wants to change the memory from nomap to pte-mapped. I'd rather warn in memblock_is_nomap() and memblock_is_llmap() if they both are set and let the caller deal with making sure they are not. > + > return memblock_setclr_flag(&memblock.memory, base, size, 1, MEMBLOCK_NOMAP); > } > > @@ -1204,6 +1214,45 @@ __init int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size) > MEMBLOCK_KHO_SCRATCH); > } > > +/** > + * memblock_mark_llmap - Mark a memory region with flag MEMBLOCK_LLMAP. > + * @base: the base phys addr of the region > + * @size: the size of the region > + * > + * If supported by the architecture, such region is mapped at the last-level in > + * the kernel direct map. > + * > + * Return: 0 on success, -errno on failure. > + */ > +int __init_memblock memblock_mark_llmap(phys_addr_t base, phys_addr_t size) > +{ > + struct memblock_region *r; > + > + memblock_cap_size(base, &size); > + > + for_each_mem_region(r) { > + if (memblock_is_nomap(r) && > + memblock_addrs_overlap(base, size, r->base, r->size)) > + return -EINVAL; > + } same here > + > + return memblock_setclr_flag(&memblock.memory, base, size, 1, > + MEMBLOCK_LLMAP); > +} > + > +/** > + * memblock_clear_llmap - Clear flag MEMBLOCK_LLMAP for a specified region. > + * @base: the base phys addr of the region > + * @size: the size of the region > + * > + * Return: 0 on success, -errno on failure. > + */ > +int __init_memblock memblock_clear_llmap(phys_addr_t base, phys_addr_t size) > +{ > + return memblock_setclr_flag(&memblock.memory, base, size, 0, > + MEMBLOCK_LLMAP); > +} > + > static bool should_skip_region(struct memblock_type *type, > struct memblock_region *m, > int nid, int flags) > @@ -2886,6 +2935,7 @@ static const char * const flagname[] = { > [ilog2(MEMBLOCK_RSRV_NOINIT)] = "RSV_NIT", > [ilog2(MEMBLOCK_RSRV_KERN)] = "RSV_KERN", > [ilog2(MEMBLOCK_KHO_SCRATCH)] = "KHO_SCRATCH", > + [ilog2(MEMBLOCK_LLMAP)] = "LLMAP", > }; > > static int memblock_debug_show(struct seq_file *m, void *private) > -- > 2.55.0.970.g62bdec98f9-goog > -- Sincerely yours, Mike.