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Wed, 5 May 2021 15:19:19 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 085D3203E67F7; Wed, 5 May 2021 15:19:19 +0200 (CEST) Date: Wed, 5 May 2021 15:19:18 +0200 From: Peter Zijlstra To: Mike Rapoport Cc: Rick Edgecombe , dave.hansen@intel.com, luto@kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com, ira.weiny@intel.com, dan.j.williams@intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 5/9] x86, mm: Use cache of page tables Message-ID: References: <20210505003032.489164-1-rick.p.edgecombe@intel.com> <20210505003032.489164-6-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 73225E000118 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b="W/WiWgFI"; dmarc=none; spf=none (imf21.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.92.199) smtp.mailfrom=peterz@infradead.org X-Rspamd-Server: rspam04 X-Stat-Signature: 8qexewuqtc1pra97brpeyr1h89k7nkqu Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=desiato.infradead.org; client-ip=90.155.92.199 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620220764-802999 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, May 05, 2021 at 03:09:09PM +0300, Mike Rapoport wrote: > On Wed, May 05, 2021 at 10:51:55AM +0200, Peter Zijlstra wrote: > > On Tue, May 04, 2021 at 05:30:28PM -0700, Rick Edgecombe wrote: > > > @@ -54,6 +98,8 @@ void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte) > > > { > > > pgtable_pte_page_dtor(pte); > > > paravirt_release_pte(page_to_pfn(pte)); > > > + /* Set Page Table so swap knows how to free it */ > > > + __SetPageTable(pte); > > > paravirt_tlb_remove_table(tlb, pte); > > > } > > > > > > @@ -70,12 +116,16 @@ void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd) > > > tlb->need_flush_all = 1; > > > #endif > > > pgtable_pmd_page_dtor(page); > > > + /* Set Page Table so swap nows how to free it */ > > > + __SetPageTable(virt_to_page(pmd)); > > > paravirt_tlb_remove_table(tlb, page); > > > } > > > > > > #if CONFIG_PGTABLE_LEVELS > 3 > > > void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud) > > > { > > > + /* Set Page Table so swap nows how to free it */ > > > + __SetPageTable(virt_to_page(pud)); > > > paravirt_release_pud(__pa(pud) >> PAGE_SHIFT); > > > paravirt_tlb_remove_table(tlb, virt_to_page(pud)); > > > } > > > @@ -83,6 +133,8 @@ void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud) > > > #if CONFIG_PGTABLE_LEVELS > 4 > > > void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d) > > > { > > > + /* Set Page Table so swap nows how to free it */ > > > + __SetPageTable(virt_to_page(p4d)); > > > paravirt_release_p4d(__pa(p4d) >> PAGE_SHIFT); > > > paravirt_tlb_remove_table(tlb, virt_to_page(p4d)); > > > } > > > > This, to me, seems like a really weird place to __SetPageTable(), why > > can't we do that on allocation? > > We call __ClearPageTable() at pgtable_pxy_page_dtor(), so at least for pte > and pmd we need to somehow tell release_pages() what kind of page it was. Hurph, right, but then the added comment is misleading; s/Set/Reset/g. Still I'm thinking that if we do these allocators, moving the set/clear to the allocator would be the most natural place, perhaps we can remove them from the {c,d}tor.