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 08B39233149 for ; Tue, 25 Aug 2026 16:46:57 +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=1787676419; cv=none; b=SPgwQAbYR9KfE55XZHKYWmxqMroVgU8ubjjbnrXyR+AKOgln/YE7K1JP1wUalfDu4j9+hXjJbMFAe7eUdG6znM+ubnWjCfpxk02znGuqErS9EMwIlTdPFyeSf3S3xzsQS0+hV1aY3L3JRzzpkUccdqGhoGFIkpDv13DY5i/0O4k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787676419; c=relaxed/simple; bh=mm9ITXr58MJRrYzaofvqA8BqsoGCzEhkttVttRGxrdQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pMKuMOzUcxdWxkLXRo9kVB9tlfkrQZKGLVRsMhMec+TA5jkbKv1uMpbBQTyxiYp5KCfx/U4Q3doR2IwZGPbubXjqFnlHHLHf9ltncr+AlZoEv4GMAwi3udb8wnIIomuNtJt4Otlr9QUxksuychaq1z8BYmoR0vOYiLnKXT130U8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A1QvjT4C; 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="A1QvjT4C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F61F1F00A3A; Tue, 25 Aug 2026 16:46:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787676417; bh=fljagmBbQwC/iRaXRhNF4fLMKhBQZFdPhsqh8nbR+XQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=A1QvjT4C2hH4HwlAkKlxYcWyc7NJSnyh31obmC1DkPVWqDcK89dcrWToUUBfqLiHc pGrP7OqyMSNK3b2H6WZQ8bOeI/ahyqXC7GDoF12FYzhyNoVEtHdSHNkH0E0Grm0Ves GHJDw/X/P914CN6y57NDnIm8ZICMmFbkfFhFAechratc0JrKodyCz7wivd7p1YdcWT zca8nPTVuDvm8iNXaOIpVnRWwMWY1OjAJ8EP1sTn+50sjK5P1ghesUTpLPgvdDCdI1 D1zUrj/QuN/cG8qkFZ/Hv9Ki23QBuXPhDduH9rs88/TlA9R1JXHOMItDD9E4YaAuv/ 2jYMB3UX+FQCQ== Message-ID: <86823e2b-f739-4ebe-b92f-a35b9dcfa0c7@kernel.org> Date: Tue, 25 Aug 2026 18:46:49 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 2/3] arm64/mm: add set_direct_map_ro_noflush() To: Will Deacon Cc: Xueyuan Chen , akpm@linux-foundation.org, ljs@kernel.org, usama.arif@linux.dev, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rppt@kernel.org, ryan.roberts@arm.com, ziy@nvidia.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lance Yang References: <20260730090647.2401252-1-xueyuan.chen21@gmail.com> <20260730090647.2401252-3-xueyuan.chen21@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/25/26 18:44, Will Deacon wrote: > On Tue, Aug 25, 2026 at 05:52:20PM +0200, David Hildenbrand (Arm) wrote: >> On 7/30/26 11:06, Xueyuan Chen wrote: >>> Implement set_direct_map_ro_noflush() for arm64 with update_range_prot() on >>> the linear map, setting PTE_RDONLY and clearing PTE_WRITE. Keep the >>> existing can_set_direct_map() guard and leave TLB invalidation to the >>> caller. >>> >>> Co-developed-by: Lance Yang >>> Signed-off-by: Lance Yang >>> Signed-off-by: Xueyuan Chen >>> --- >>> arch/arm64/include/asm/set_memory.h | 2 ++ >>> arch/arm64/mm/pageattr.c | 10 ++++++++++ >>> 2 files changed, 12 insertions(+) >>> >>> diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h >>> index 90f61b17275e..7083260303c3 100644 >>> --- a/arch/arm64/include/asm/set_memory.h >>> +++ b/arch/arm64/include/asm/set_memory.h >>> @@ -14,6 +14,8 @@ int set_memory_valid(unsigned long addr, int numpages, int enable); >>> int set_direct_map_invalid_noflush(struct page *page); >>> int set_direct_map_default_noflush(struct page *page); >>> int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); >>> +int set_direct_map_ro_noflush(const void *addr, unsigned long nr_pages); >>> +#define set_direct_map_ro_noflush set_direct_map_ro_noflush >>> bool kernel_page_present(struct page *page); >>> >>> int set_memory_encrypted(unsigned long addr, int numpages); >>> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c >>> index ce035e1b4eaf..c51236b61651 100644 >>> --- a/arch/arm64/mm/pageattr.c >>> +++ b/arch/arm64/mm/pageattr.c >>> @@ -365,6 +365,16 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid) >>> return set_memory_valid(addr, nr, valid); >>> } >>> >>> +int set_direct_map_ro_noflush(const void *addr, unsigned long nr_pages) >>> +{ >>> + if (!can_set_direct_map()) >>> + return 0; >>> + >>> + return update_range_prot((unsigned long)addr, PAGE_SIZE * nr_pages, >>> + __pgprot(PTE_RDONLY), >>> + __pgprot(PTE_WRITE)); >>> +} >>> + >>> #ifdef CONFIG_DEBUG_PAGEALLOC >>> /* >>> * This is - apart from the return value - doing the same >> >> We'll need an ACK from arm64 maintaines. To me this looks good. > > I generally dislike deferring critical things like TLB invalidation to > the caller, so it would be good to see an example of a caller that really > needs that. The caller in patch 1 unconditionally calls > flush_tlb_kernel_range() immediately after calling > set_direct_map_ro_noflush(). > > In fact, that means we have a pointless invalidation if > !can_set_direct_map(). See exhibit A :) Ack. I recall that the patch set originally didn't do any flushes, but we really have to flush even though we are early during boot. So agreed, the interface should just flush internally. -- Cheers, David