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Wed, 5 May 2021 10:51:55 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A4A472D74E1CF; Wed, 5 May 2021 10:51:55 +0200 (CEST) Date: Wed, 5 May 2021 10:51:55 +0200 From: Peter Zijlstra To: Rick Edgecombe Cc: 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, rppt@kernel.org, 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: <20210505003032.489164-6-rick.p.edgecombe@intel.com> X-Rspamd-Queue-Id: D357C40002E3 Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=TtiWTgZU; dmarc=none; spf=none (imf26.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-Rspamd-Server: rspam04 X-Stat-Signature: smb7f7ofn1yb3j68d919ht8coejxgxj6 Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf26; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620204751-873168 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 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? > @@ -888,6 +889,12 @@ void release_pages(struct page **pages, int nr) > continue; > } > > + if (PageTable(page)) { > + __ClearPageTable(page); > + free_table(page); > + continue; > + } > + > if (!put_page_testzero(page)) > continue; > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index 3cdee7b11da9..a60ec3d4ab21 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -22,6 +22,7 @@ > #include > #include > #include > +#include > #include "internal.h" > > /* > @@ -310,6 +311,11 @@ static inline void free_swap_cache(struct page *page) > void free_page_and_swap_cache(struct page *page) > { > free_swap_cache(page); > + if (PageTable(page)) { > + __ClearPageTable(page); > + free_table(page); > + return; > + } > if (!is_huge_zero_page(page)) > put_page(page); > } And then free_table() can __ClearPageTable() and all is nice and symmetric and all this weirdness goes away, no?