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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-452137290b9sm141807225e9.34.2025.06.10.06.14.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Jun 2025 06:14:48 -0700 (PDT) Message-ID: <1b94d8ce-ab6c-417d-af4e-cd49bf297b60@redhat.com> Date: Tue, 10 Jun 2025 15:14:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] arm64: pageattr: Use walk_page_range_novma() to change memory permissions To: Dev Jain , akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, steven.price@arm.com, gshan@redhat.com, linux-arm-kernel@lists.infradead.org, yang@os.amperecomputing.com, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20250610114401.7097-1-dev.jain@arm.com> <20250610114401.7097-3-dev.jain@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250610_061453_973861_E3704A56 X-CRM114-Status: GOOD ( 22.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10.06.25 13:44, Dev Jain wrote: Subject seems outdated: walk_kernel_page_table_range() > Since apply_to_page_range does not support operations on block mappings, > use the generic pagewalk API to enable changing permissions for kernel > block mappings. This paves the path for enabling huge mappings by default > on kernel space mappings, thus leading to more efficient TLB usage. > > We only require that the start and end of a given range lie on leaf mapping > boundaries. Return EINVAL in case a partial block mapping is detected; add > a corresponding comment in ___change_memory_common() to warn that > eliminating such a condition is the responsibility of the caller. > > apply_to_page_range ultimately uses the lazy MMU hooks at the pte level > function (apply_to_pte_range) - we want to use this functionality after > this patch too. Ryan says: > "The only reason we traditionally confine the lazy mmu mode to a single > page table is because we want to enclose it within the PTL. But that > requirement doesn't stand for kernel mappings. As long as the walker can > guarantee that it doesn't allocate any memory (because with certain debug > settings that can cause lazy mmu nesting) or try to sleep then I think we > can just bracket the entire call." > Therefore, wrap the call to walk_kernel_page_table_range() with the > lazy MMU helpers. > > Signed-off-by: Dev Jain > --- > arch/arm64/mm/pageattr.c | 158 +++++++++++++++++++++++++++++++-------- > 1 file changed, 126 insertions(+), 32 deletions(-) > > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > index 04d4a8f676db..2c118c0922ef 100644 > --- a/arch/arm64/mm/pageattr.c > +++ b/arch/arm64/mm/pageattr.c > @@ -8,6 +8,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -20,6 +21,100 @@ struct page_change_data { > pgprot_t clear_mask; > }; > The general idea looks sane to me. -- Cheers, David / dhildenb