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Thu, 9 Feb 2023 03:11:18 -0500 (EST) Received: by box.shutemov.name (Postfix, from userid 1000) id A2F5C109CAF; Thu, 9 Feb 2023 11:11:14 +0300 (+03) Date: Thu, 9 Feb 2023 11:11:14 +0300 From: "Kirill A. Shutemov" To: Matthew Wilcox Cc: Yin Fengwei , linux-mm@kvack.org, david@redhat.com, dave.hansen@intel.com, tim.c.chen@intel.com, ying.huang@intel.com Subject: Re: [PATCH v5 2/5] mm: Add generic set_ptes() Message-ID: <20230209081114.7y2u3idlm54br6wz@box.shutemov.name> References: <20230207194937.122543-1-willy@infradead.org> <20230207194937.122543-3-willy@infradead.org> <20230208083848.craqlaft2xtmchwf@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 20CE74000A X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 835emcstp6zhukmzzwc16w9phfd7eysz X-HE-Tag: 1675930280-112271 X-HE-Meta: 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 kXo6szPs jxkKmBUNiydpnB2FmI68bSN+eOVKF11pEjf8LZ0KHeGSgkBB5J9Ff3xd4zlU2L6ABmvG/k4h5X2jAXLZEQOsn1RXo1yEpR+zVC8XE1FuAKITvQ6/4MfFA04wlrwFNNYIPOCE/uK2+vU3LSeca2vRBQlkWCxvBqF7BcWXXaEBqI8Yu4eOK7zR2ss6SpxJajD4wQXQkJnQZcO3E0Z03XBsWug+OSVaNUnHIvUHWLxaGKv5DkMam4+8PyMDxZ+g2rMXgIoUYX/h2a6KKXBztMA+qmhhRJrS27eL7fvjRdGiOtyM/PXdTKhmNESV1j302jgyV96rYcCGUraj/l70sbflMAtTCEyNv7fEHroolMtDlHzoSdRo= 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 Wed, Feb 08, 2023 at 06:14:48PM +0000, Matthew Wilcox wrote: > On Wed, Feb 08, 2023 at 11:38:48AM +0300, Kirill A. Shutemov wrote: > > > +static inline void set_ptes(struct mm_struct *mm, unsigned long addr, > > > + pte_t *ptep, pte_t pte, unsigned int nr) > > > +{ > > > + for (;;) { > > > + set_pte_at(mm, addr, ptep, pte); > > > + if (--nr == 0) > > > + break; > > > > Maybe do { ... } while (--nr); instead of the for()? > > Seems unnecessary to do the extra calculation to advance pte if > we're not going to use it? It should be transparent to compiler, but okay. > > > > + ptep++; > > > + addr += PAGE_SIZE; > > > + /* This works for x86. Check how PTEs are encoded */ > > > + pte = __pte(pte_val(pte) + PAGE_SIZE); > > > > Looks like it deserves own helper. Something like > > > > pte = pte_next(pte); > > Maybe, but then it needs to be added to each arch, which I was trying > to avoid. That said, I had another idea which I like better; more > patches coming soon. Generic pte_next() that does the "+ PAGE_SIZE" trick should be fine. Arch code can override it if bit placement is different, instead of rewriting whole set_ptes()' > Here's a sneak preview: > > +++ b/arch/x86/include/asm/pgtable.h > @@ -1019,13 +1019,22 @@ static inline pud_t native_local_pudp_get_and_clear(pud_ > t *pudp) > return res; > } > > -static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, > - pte_t *ptep, pte_t pte) > +static inline void set_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, pte_t pte, unsigned int nr) > { > - page_table_check_ptes_set(mm, addr, ptep, pte, 1); > - set_pte(ptep, pte); > + page_table_check_ptes_set(mm, addr, ptep, pte, nr); > + > + for (;;) { > + set_pte(ptep, pte); > + if (--nr == 0) > + break; > + ptep++; > + pte = __pte(pte_val(pte) + PAGE_SIZE); > + } for(; nr; nr--, ptep++, pte = pte_next(pte)) set_pte(ptep, pte); Hm? > } > > +#define set_pte_at(mm, addr, ptep, pte) set_ptes(mm, addr, ptep, pte, 1) > + > static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr, > pmd_t *pmdp, pmd_t pmd) > { > > > -- Kiryl Shutsemau / Kirill A. Shutemov