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[79.241.253.87]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ee0fbd63a2sm22761239f8f.48.2025.09.23.01.04.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Sep 2025 01:04:29 -0700 (PDT) Message-ID: <5ec85b0b-9848-4cee-98f4-37953d504773@redhat.com> Date: Tue, 23 Sep 2025 10:04:27 +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 v7 10/16] mm: define clear_pages(), clear_user_pages() To: Ankur Arora , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: akpm@linux-foundation.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, mjguzik@gmail.com, luto@kernel.org, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com References: <20250917152418.4077386-1-ankur.a.arora@oracle.com> <20250917152418.4077386-11-ankur.a.arora@oracle.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.09.25 17:24, Ankur Arora wrote: > Define fallback versions of clear_pages(), clear_user_pages(). > > In absence of architectural primitives, we just clear pages > sequentially. > > Signed-off-by: Ankur Arora > --- > include/linux/mm.h | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1ae97a0b8ec7..0cde9b01da5e 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3768,6 +3768,44 @@ static inline void clear_page_guard(struct zone *zone, struct page *page, > unsigned int order) {} > #endif /* CONFIG_DEBUG_PAGEALLOC */ > > +#ifndef clear_pages > +/** > + * clear_pages() - clear a page range using a kernel virtual address. I'd just call this "clear a page range for kernel-internal use" > + * @addr: start address > + * @npages: number of pages > + * > + * Assumes that (@addr, +@npages) references a kernel region. And say here simply that "Use clear_user_pages() instead for clearing a page range to be mapped to user space". > + * Does absolutely no exception handling. > + */ > +static inline void clear_pages(void *addr, unsigned int npages) > +{ > + do { > + clear_page(addr); > + addr += PAGE_SIZE; > + } while (--npages); > +} > +#endif > + > +#ifndef clear_user_pages > +/** > + * clear_user_pages() - clear a page range mapped by the user. I'd call this then "clear a page range to be mapped to user space" Because it's usually called before we actually map it and it will properly flush the dcache if required. > + * @addr: kernel mapped address "start address" > + * @vaddr: user mapped address "start address of the user mapping" ? > + * @pg: start page Please just call it "page". I know, clear_user_page() has this weird page vs. pg thingy, but let's do it better here. > + * @npages: number of pages > + * > + * Assumes that the region (@addr, +@npages) has been validated > + * already so this does no exception handling. > + */ > +#define clear_user_pages(addr, vaddr, pg, npages) \ > +do { \ > + clear_user_page(addr, vaddr, pg); \ > + addr += PAGE_SIZE; \ > + vaddr += PAGE_SIZE; \ > + pg++; \ > +} while (--npages) > +#endif Should indent with one tab. Any reason this is not a static inline function? -- Cheers David / dhildenb