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Wed, 05 May 2021 13:19:20 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 4C2143001CD; 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: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.