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[60.242.11.44]) by smtp.gmail.com with ESMTPSA id x17sm3714593pff.180.2021.02.03.19.23.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 19:23:24 -0800 (PST) Date: Thu, 04 Feb 2021 13:23:18 +1000 From: Nicholas Piggin Subject: Re: [PATCH] mm/memory.c: Remove pte_sw_mkyoung() To: Andrew Morton , Christophe Leroy Cc: Jia He , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Bibo Mao , Thomas Bogendoerfer References: <20210203164630.ada46d0c84e0e9f0a474b283@linux-foundation.org> In-Reply-To: <20210203164630.ada46d0c84e0e9f0a474b283@linux-foundation.org> MIME-Version: 1.0 Message-Id: <1612408831.1l3aypsvyz.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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: Excerpts from Andrew Morton's message of February 4, 2021 10:46 am: > On Wed, 3 Feb 2021 10:19:44 +0000 (UTC) Christophe Leroy wrote: >=20 >> Commit 83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF >> is cleared") introduced arch_faults_on_old_pte() helper to identify >> platforms that don't set page access bit in HW and require a page >> fault to set it. >>=20 >> Commit 44bf431b47b4 ("mm/memory.c: Add memory read privilege on page >> fault handling") added pte_sw_mkyoung() which is yet another way to >> manage platforms that don't set page access bit in HW and require a >> page fault to set it. >>=20 >> Remove that pte_sw_mkyoung() helper and use the already existing >> arch_faults_on_old_pte() helper together with pte_mkyoung() instead. >=20 > This conflicts with mm/memory.c changes in linux-next. In > do_set_pte(). Please check my efforts: I wanted to just get rid of it completely -- https://marc.info/?l=3Dlinux-mm&m=3D160860750115163&w=3D2 Waiting for MIPs to get that patch mentioned merged or nacked but as yet seems to be no response from maintainers. https://lore.kernel.org/linux-arch/20201019081257.32127-1-huangpei@loongson= .cn/ Thanks, Nick >=20 > --- a/arch/mips/include/asm/pgtable.h~mm-memoryc-remove-pte_sw_mkyoung > +++ a/arch/mips/include/asm/pgtable.h > @@ -406,8 +406,6 @@ static inline pte_t pte_mkyoung(pte_t pt > return pte; > } > =20 > -#define pte_sw_mkyoung pte_mkyoung > - > #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT > static inline int pte_huge(pte_t pte) { return pte_val(pte) & _PAGE_HUGE= ; } > =20 > --- a/include/linux/pgtable.h~mm-memoryc-remove-pte_sw_mkyoung > +++ a/include/linux/pgtable.h > @@ -424,22 +424,6 @@ static inline void ptep_set_wrprotect(st > } > #endif > =20 > -/* > - * On some architectures hardware does not set page access bit when acce= ssing > - * memory page, it is responsibilty of software setting this bit. It bri= ngs > - * out extra page fault penalty to track page access bit. For optimizati= on page > - * access bit can be set during all page fault flow on these arches. > - * To be differentiate with macro pte_mkyoung, this macro is used on pla= tforms > - * where software maintains page access bit. > - */ > -#ifndef pte_sw_mkyoung > -static inline pte_t pte_sw_mkyoung(pte_t pte) > -{ > - return pte; > -} > -#define pte_sw_mkyoung pte_sw_mkyoung > -#endif > - > #ifndef pte_savedwrite > #define pte_savedwrite pte_write > #endif > --- a/mm/memory.c~mm-memoryc-remove-pte_sw_mkyoung > +++ a/mm/memory.c > @@ -2902,7 +2902,8 @@ static vm_fault_t wp_page_copy(struct vm > } > flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); > entry =3D mk_pte(new_page, vma->vm_page_prot); > - entry =3D pte_sw_mkyoung(entry); > + if (arch_faults_on_old_pte()) > + entry =3D pte_mkyoung(entry); > entry =3D maybe_mkwrite(pte_mkdirty(entry), vma); > =20 > /* > @@ -3560,7 +3561,8 @@ static vm_fault_t do_anonymous_page(stru > __SetPageUptodate(page); > =20 > entry =3D mk_pte(page, vma->vm_page_prot); > - entry =3D pte_sw_mkyoung(entry); > + if (arch_faults_on_old_pte()) > + entry =3D pte_mkyoung(entry); > if (vma->vm_flags & VM_WRITE) > entry =3D pte_mkwrite(pte_mkdirty(entry)); > =20 > @@ -3745,8 +3747,8 @@ void do_set_pte(struct vm_fault *vmf, st > =20 > if (prefault && arch_wants_old_prefaulted_pte()) > entry =3D pte_mkold(entry); > - else > - entry =3D pte_sw_mkyoung(entry); > + else if (arch_faults_on_old_pte()) > + entry =3D pte_mkyoung(entry); > =20 > if (write) > entry =3D maybe_mkwrite(pte_mkdirty(entry), vma); > _ >=20 >=20 >=20