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[104.155.91.135]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4858d312ca0sm27142034f8f.4.2026.09.07.02.50.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Sep 2026 02:50:15 -0700 (PDT) Date: Mon, 7 Sep 2026 10:50:12 +0100 From: Vincent Donnefort To: Mike Rapoport 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: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EF6AD20009 X-Stat-Signature: bpuyma7peqgzcmwyxgprghe98xmx63ic X-Rspam-User: X-HE-Tag: 1788774617-134921 X-HE-Meta: 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 v9FDMAX5 38YyuLvC/r5CpIcLfklqwNjyd1Va3kIBGY12iKp4uzt9PzhCZleLQ8Oo9rbRxgXbIdnG3jSg0eziqfMe4VkmYHNekWXbtiNTy3Taw91slZzfXN6nvbpDnjVnX0m35rOM5k2RxV1/edQ6lTR15ym64xUriKzuwwKNwqq4AreShCpiK1mkYRx98tjVry5eVObUMSuLeme4mn0awEsLC4AndGkon4RdsbMhOP2eVDbKCcVAkLvjeM6thq8yd7iP/vXzjI9UkbliMXWCZnJ26PHChsfAU4Eu6JRwMA3ak+s3ypGh+899QAYz1Fp+IaZH97I3BKfnKQLjgcKCj2bxhTL9BRAwVaxj4DR8CVw0097+YFIb2m3o84gS16t1f5jCX6mgIDhCsXx7z2ac2e5EotArsJxpRmw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Sep 06, 2026 at 10:33:11PM +0300, Mike Rapoport wrote: > 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. The idea was to have something close from NOMAP, to emphasis it is one or the other. But PTE_MAP sounds good too. > > > 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. ack. > > > + > > 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 ack > > > + > > + 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. -- Vincent