From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F37004964F; Sun, 6 Sep 2026 19:33:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788723202; cv=none; b=TFmsKUVbJG02VO09W4K+RCqKKe5Y32GKMgDUeLSOwNM6aHMvP+CyEsbK7A5jDPbnJUlEc6JdbPz86cUKIfGyHo3j9i+fPomQaehzeyH7fQwyUptNaYKDW0Bu0eVJbUCP8wx0JnxNUjr7mgbpqiawb+5LM3XmuHpN0g6UoBcCkMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788723202; c=relaxed/simple; bh=Do2CEdD6a5aUwLTxegZNZ7rZH9H8xfi1JGY3Uv4qcvI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=SJ4jj+ZLw9E5BP8B+bqf4SxBxJJ5P4s6AZGN3g6jmn2aDw8GjQaIW2EvCMbaeZuiGABE8lX4ql9uG3avd8rHsFtJTBvxUl1Sy1pcfKBzTdF92F/bn0osUYjaYIGiXJwRwDpRTrjQoiaZ9fp5K8aCv2lmEEYhZkPKYU2YiWycm9Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UOQ+l3C3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UOQ+l3C3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB2B71F00A3A; Sun, 6 Sep 2026 19:33:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788723200; bh=0kNqOTPkZp3J7RemsYmMnYNi7t0didLL0edZoqZbuyw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260902104712.2399797-2-vdonnefort@google.com> 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.