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Mon, 8 Mar 2021 11:00:20 +0000 (UTC) Received: from [10.36.113.123] (ovpn-113-123.ams2.redhat.com [10.36.113.123]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8F27269C83; Mon, 8 Mar 2021 11:00:18 +0000 (UTC) Subject: Re: [PATCH] arm64: mte: Use PAGE_KERNEL_TAGGED in arch_add_memory To: Catalin Marinas Cc: Patrick Daly , linux-arm-kernel@lists.infradead.org, Will Deacon , Vincenzo Frascino , Anshuman Khandual , linux-mm@kvack.org References: <1614745263-27827-1-git-send-email-pdaly@codeaurora.org> <20210305111908.GA23855@arm.com> <20210305154340.GC23855@arm.com> <3dae4529-6c73-d4c0-3fa6-6c2bda6518c9@redhat.com> <20210305174413.GF23855@arm.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <23d7530f-20cf-f7bb-b4e3-0a75606f0b19@redhat.com> Date: Mon, 8 Mar 2021 12:00:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210305174413.GF23855@arm.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: CFA786000100 X-Stat-Signature: sa15cf67gzbjitzyeh1ghixu3w3buzcz Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf25; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615201222-283796 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: On 05.03.21 18:44, Catalin Marinas wrote: > On Fri, Mar 05, 2021 at 04:55:28PM +0100, David Hildenbrand wrote: >> On 05.03.21 16:43, Catalin Marinas wrote: >>> On Fri, Mar 05, 2021 at 11:19:08AM +0000, Catalin Marinas wrote: >>>> On Tue, Mar 02, 2021 at 08:21:03PM -0800, Patrick Daly wrote: >>>>> In a system which supports MTE, the linear kernel region must allow >>>>> reading/writing allocation tags. For memory present at boot this >>>>> is already being done in map_mem(). Add the same in arch_add_memory(). >>>>> >>>>> Signed-off-by: Patrick Daly >>>>> --- >>>>> arch/arm64/mm/mmu.c | 12 +++++++++++- >>>>> 1 file changed, 11 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>>>> index 9b25d60b..0fcfe90 100644 >>>>> --- a/arch/arm64/mm/mmu.c >>>>> +++ b/arch/arm64/mm/mmu.c >>>>> @@ -1463,6 +1463,7 @@ int arch_add_memory(int nid, u64 start, u64 size, >>>>> struct mhp_params *params) >>>>> { >>>>> int ret, flags = 0; >>>>> + pgprot_t pgprot; >>>>> if (!inside_linear_region(start, size)) { >>>>> pr_err("[%llx %llx] is outside linear mapping region\n", start, start + size); >>>>> @@ -1477,8 +1478,17 @@ int arch_add_memory(int nid, u64 start, u64 size, >>>>> IS_ENABLED(CONFIG_KFENCE)) >>>>> flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>>>> + /* >>>>> + * The linear map must allow allocation tags reading/writing >>>>> + * if MTE is present. Otherwise, it has the same attributes as >>>>> + * PAGE_KERNEL. >>>>> + */ >>>>> + pgprot = params->pgprot; >>>>> + if (pgprot_val(pgprot) == pgprot_val(PAGE_KERNEL)) >>>>> + pgprot = PAGE_KERNEL_TAGGED; >>>>> + >>>>> __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start), >>>>> - size, params->pgprot, __pgd_pgtable_alloc, >>>>> + size, pgprot, __pgd_pgtable_alloc, >>>>> flags); > [...] >>> ---------------8<------------------------------- >>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >>> index e17b96d0e4b5..5c78b92d9ec5 100644 >>> --- a/arch/arm64/include/asm/pgtable.h >>> +++ b/arch/arm64/include/asm/pgtable.h >>> @@ -486,6 +486,8 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd) >>> __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_NC) | PTE_PXN | PTE_UXN) >>> #define pgprot_device(prot) \ >>> __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_DEVICE_nGnRE) | PTE_PXN | PTE_UXN) >>> +#define pgprot_tagged(prot) \ >>> + __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_TAGGED)) >>> /* >>> * DMA allocations for non-coherent devices use what the Arm architecture calls >>> * "Normal non-cacheable" memory, which permits speculation, unaligned accesses >>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>> index cdfc4e9f253e..f5f5044db2ce 100644 >>> --- a/include/linux/pgtable.h >>> +++ b/include/linux/pgtable.h >>> @@ -904,6 +904,10 @@ static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, >>> #define pgprot_device pgprot_noncached >>> #endif >>> >>> +#ifndef pgprot_tagged >>> +#define pgprot_tagged(prot) (prot) >>> +#endif >>> + >>> #ifdef CONFIG_MMU >>> #ifndef pgprot_modify >>> #define pgprot_modify pgprot_modify >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 5ba51a8bdaeb..4253d80a59ba 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -1072,7 +1072,7 @@ static int online_memory_block(struct memory_block *mem, void *arg) >>> */ >>> int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) >>> { >>> - struct mhp_params params = { .pgprot = PAGE_KERNEL }; >>> + struct mhp_params params = { .pgprot = pgprot_tagged(PAGE_KERNEL) }; >> >> This looks like we're pushing arch specific stuff ("tagged") in here. Can't >> we generalize this to something like >> >> pgprot_mhp_default >> >> (or a better name) >> >> that defaults to PAGE_KERNEL on all architectures except arm64 which >> overwrites this somehow? > > It works for me but I prefer the prot modification style similar to > pgprot_writecombine() etc. (i.e. takes a parameter like PAGE_KERNEL and > just changes bits of it). Sure, I'm wondering if we can abstract the "tagged" part here. pgprot_mhp(PAGE_KERNEL) whatsoever. But maybe we do consider the "tagged" part okay in common code already (it felt quite arm64 specific to me at first). I can spot untagged_addr() all over the place. So maybe pgprot_tagged() is just fine. -- Thanks, David / dhildenb