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[34.82.181.220]) by smtp.gmail.com with ESMTPSA id y186-20020a6232c3000000b00535e46171c1sm8503863pfy.117.2022.09.13.17.49.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Sep 2022 17:49:30 -0700 (PDT) Date: Tue, 13 Sep 2022 17:49:27 -0700 From: Ricardo Koller To: Oliver Upton Subject: Re: [PATCH 09/14] KVM: arm64: Free removed stage-2 tables in RCU callback Message-ID: References: <20220830194132.962932-1-oliver.upton@linux.dev> <20220830194132.962932-10-oliver.upton@linux.dev> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220830194132.962932-10-oliver.upton@linux.dev> Cc: kvm@vger.kernel.org, Marc Zyngier , linux-kernel@vger.kernel.org, Ben Gardon , Catalin Marinas , David Matlack , Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Oliver, On Tue, Aug 30, 2022 at 07:41:27PM +0000, Oliver Upton wrote: > There is no real urgency to free a stage-2 subtree that was pruned. > Nonetheless, KVM does the tear down in the stage-2 fault path while > holding the MMU lock. > > Free removed stage-2 subtrees after an RCU grace period. To guarantee > all stage-2 table pages are freed before killing a VM, add an > rcu_barrier() to the flush path. > > Signed-off-by: Oliver Upton > --- > arch/arm64/kvm/mmu.c | 35 ++++++++++++++++++++++++++++++++++- > 1 file changed, 34 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 91521f4aab97..265951c05879 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -97,6 +97,38 @@ static void *stage2_memcache_zalloc_page(void *arg) > return kvm_mmu_memory_cache_alloc(mc); > } > > +#define STAGE2_PAGE_PRIVATE_LEVEL_MASK GENMASK_ULL(2, 0) > + > +static inline unsigned long stage2_page_private(u32 level, void *arg) > +{ > + unsigned long pvt = (unsigned long)arg; > + > + BUILD_BUG_ON(KVM_PGTABLE_MAX_LEVELS > STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + WARN_ON_ONCE(pvt & STAGE2_PAGE_PRIVATE_LEVEL_MASK); If the pgt pointer (arg) is not aligned for some reason, I think it might be better to BUG_ON(). Alternatively, why not trying to pass a new struct (with level and arg) that's freed by the rcu callback. > + > + return pvt | level; > +} > + > +static void stage2_free_removed_table_rcu_cb(struct rcu_head *head) > +{ > + struct page *page = container_of(head, struct page, rcu_head); > + unsigned long pvt = page_private(page); > + void *arg = (void *)(pvt & ~STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + u32 level = (u32)(pvt & STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + void *pgtable = page_to_virt(page); > + > + kvm_pgtable_stage2_free_removed(pgtable, level, arg); > +} > + > +static void stage2_free_removed_table(void *pgtable, u32 level, void *arg) > +{ > + unsigned long pvt = stage2_page_private(level, arg); > + struct page *page = virt_to_page(pgtable); > + > + set_page_private(page, (unsigned long)pvt); > + call_rcu(&page->rcu_head, stage2_free_removed_table_rcu_cb); > +} > + > static void *kvm_host_zalloc_pages_exact(size_t size) > { > return alloc_pages_exact(size, GFP_KERNEL_ACCOUNT | __GFP_ZERO); > @@ -627,7 +659,7 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = { > .zalloc_page = stage2_memcache_zalloc_page, > .zalloc_pages_exact = kvm_host_zalloc_pages_exact, > .free_pages_exact = free_pages_exact, > - .free_removed_table = kvm_pgtable_stage2_free_removed, > + .free_removed_table = stage2_free_removed_table, > .get_page = kvm_host_get_page, > .put_page = kvm_host_put_page, > .page_count = kvm_host_page_count, > @@ -770,6 +802,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) > if (pgt) { > kvm_pgtable_stage2_destroy(pgt); > kfree(pgt); > + rcu_barrier(); > } > } > > -- > 2.37.2.672.g94769d06f0-goog > _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DD8F5C54EE9 for ; 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[34.82.181.220]) by smtp.gmail.com with ESMTPSA id y186-20020a6232c3000000b00535e46171c1sm8503863pfy.117.2022.09.13.17.49.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Sep 2022 17:49:30 -0700 (PDT) Date: Tue, 13 Sep 2022 17:49:27 -0700 From: Ricardo Koller To: Oliver Upton Cc: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , Will Deacon , Quentin Perret , Reiji Watanabe , David Matlack , Ben Gardon , Paolo Bonzini , Gavin Shan , Peter Xu , Sean Christopherson , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 09/14] KVM: arm64: Free removed stage-2 tables in RCU callback Message-ID: References: <20220830194132.962932-1-oliver.upton@linux.dev> <20220830194132.962932-10-oliver.upton@linux.dev> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220830194132.962932-10-oliver.upton@linux.dev> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220913_174932_829393_DC6A84A4 X-CRM114-Status: GOOD ( 24.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Oliver, On Tue, Aug 30, 2022 at 07:41:27PM +0000, Oliver Upton wrote: > There is no real urgency to free a stage-2 subtree that was pruned. > Nonetheless, KVM does the tear down in the stage-2 fault path while > holding the MMU lock. > > Free removed stage-2 subtrees after an RCU grace period. To guarantee > all stage-2 table pages are freed before killing a VM, add an > rcu_barrier() to the flush path. > > Signed-off-by: Oliver Upton > --- > arch/arm64/kvm/mmu.c | 35 ++++++++++++++++++++++++++++++++++- > 1 file changed, 34 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 91521f4aab97..265951c05879 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -97,6 +97,38 @@ static void *stage2_memcache_zalloc_page(void *arg) > return kvm_mmu_memory_cache_alloc(mc); > } > > +#define STAGE2_PAGE_PRIVATE_LEVEL_MASK GENMASK_ULL(2, 0) > + > +static inline unsigned long stage2_page_private(u32 level, void *arg) > +{ > + unsigned long pvt = (unsigned long)arg; > + > + BUILD_BUG_ON(KVM_PGTABLE_MAX_LEVELS > STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + WARN_ON_ONCE(pvt & STAGE2_PAGE_PRIVATE_LEVEL_MASK); If the pgt pointer (arg) is not aligned for some reason, I think it might be better to BUG_ON(). Alternatively, why not trying to pass a new struct (with level and arg) that's freed by the rcu callback. > + > + return pvt | level; > +} > + > +static void stage2_free_removed_table_rcu_cb(struct rcu_head *head) > +{ > + struct page *page = container_of(head, struct page, rcu_head); > + unsigned long pvt = page_private(page); > + void *arg = (void *)(pvt & ~STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + u32 level = (u32)(pvt & STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + void *pgtable = page_to_virt(page); > + > + kvm_pgtable_stage2_free_removed(pgtable, level, arg); > +} > + > +static void stage2_free_removed_table(void *pgtable, u32 level, void *arg) > +{ > + unsigned long pvt = stage2_page_private(level, arg); > + struct page *page = virt_to_page(pgtable); > + > + set_page_private(page, (unsigned long)pvt); > + call_rcu(&page->rcu_head, stage2_free_removed_table_rcu_cb); > +} > + > static void *kvm_host_zalloc_pages_exact(size_t size) > { > return alloc_pages_exact(size, GFP_KERNEL_ACCOUNT | __GFP_ZERO); > @@ -627,7 +659,7 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = { > .zalloc_page = stage2_memcache_zalloc_page, > .zalloc_pages_exact = kvm_host_zalloc_pages_exact, > .free_pages_exact = free_pages_exact, > - .free_removed_table = kvm_pgtable_stage2_free_removed, > + .free_removed_table = stage2_free_removed_table, > .get_page = kvm_host_get_page, > .put_page = kvm_host_put_page, > .page_count = kvm_host_page_count, > @@ -770,6 +802,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) > if (pgt) { > kvm_pgtable_stage2_destroy(pgt); > kfree(pgt); > + rcu_barrier(); > } > } > > -- > 2.37.2.672.g94769d06f0-goog > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B885C54EE9 for ; Wed, 14 Sep 2022 00:49:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229701AbiINAtg (ORCPT ); Tue, 13 Sep 2022 20:49:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229523AbiINAtd (ORCPT ); Tue, 13 Sep 2022 20:49:33 -0400 Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA9D5DEF for ; Tue, 13 Sep 2022 17:49:31 -0700 (PDT) Received: by mail-pl1-x629.google.com with SMTP id p18so13514357plr.8 for ; Tue, 13 Sep 2022 17:49:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=VC9mI68no/Lhw0HfZpwkORWcc1RC3UZIYHwVkfGB/r4=; b=hrIqf5MD/xB/9myyBeSm33TcaOokPoX7OBfouhtK+QYu3xN2uBJxyO2hwvyYtuh2W0 RdwXYSsNmn+DsH/Gpdq5vM3R8ZfCoKhKciL2HGbxoduQKF7c8ktRoTQjLfMESLPFpZyL Ns0E2DVLJos2dtMmG5R41fTtTe3J/4Tlo1NyAQwzTGqI70CMfMYO11+ICelzhKCetwtW SkPeKYcul80lg+mpqpXs6SCD0MpG3NKQFFzJeeWkjLD0aS7zcXg0vSm1kwe5vEoNUwPa CPS85UG7CF4R83h+gydjSaaK82yV2BkpbSMULGBFAaCTe6LmRRsym1vdrmpcBBksyYr9 H8nQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=VC9mI68no/Lhw0HfZpwkORWcc1RC3UZIYHwVkfGB/r4=; b=SWI3JUMigYETA/xQiEs24dDS2n2GRhXkVkdRSyz5v52plhiZIwqYb7tCuf9z2cqk16 uurfhBDMAWpwfT/z6lXMw2Bjz4/UKxkNVgMv1BWsJwOpFsl1NK1QqAY9Hg1Ti288Sf5M kdExnDYPF8F23QCWYMG+GW9JvcEHK9hZomVTRFVcRIaVrAM+InVBbNCEsuBRvWEv8aAb FX4IcYbtyyuXBiAACx8rapAoa6b9DB/w/6/Wgj/LdRaLDS05ZO4p3gxomGwCum8wqmZT fDoZs3YKXXpW5ocZD/1wl5HD98KQpyhEVvp6AJ5cD76Vi3VBEKyYN9cvkCkCAgcPdLrR TA2A== X-Gm-Message-State: ACrzQf2zoR/HBPnST6VXb+xaH5VQ+qe8os/vqJDC/IDDCGyDCX/jd0eM sftOPVjQs6hEhcM3eR7QG3GTQg== X-Google-Smtp-Source: AMsMyM526FQxM1WokLTXGOLY1vbfrlIhdoLZtMq7zQSlveMaKcR+WWo9mX4QO1UTnf2rxrP+iQLIoA== X-Received: by 2002:a17:90a:7006:b0:200:aabc:891 with SMTP id f6-20020a17090a700600b00200aabc0891mr1948603pjk.67.1663116571104; Tue, 13 Sep 2022 17:49:31 -0700 (PDT) Received: from google.com (220.181.82.34.bc.googleusercontent.com. [34.82.181.220]) by smtp.gmail.com with ESMTPSA id y186-20020a6232c3000000b00535e46171c1sm8503863pfy.117.2022.09.13.17.49.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Sep 2022 17:49:30 -0700 (PDT) Date: Tue, 13 Sep 2022 17:49:27 -0700 From: Ricardo Koller To: Oliver Upton Cc: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , Will Deacon , Quentin Perret , Reiji Watanabe , David Matlack , Ben Gardon , Paolo Bonzini , Gavin Shan , Peter Xu , Sean Christopherson , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 09/14] KVM: arm64: Free removed stage-2 tables in RCU callback Message-ID: References: <20220830194132.962932-1-oliver.upton@linux.dev> <20220830194132.962932-10-oliver.upton@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220830194132.962932-10-oliver.upton@linux.dev> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Oliver, On Tue, Aug 30, 2022 at 07:41:27PM +0000, Oliver Upton wrote: > There is no real urgency to free a stage-2 subtree that was pruned. > Nonetheless, KVM does the tear down in the stage-2 fault path while > holding the MMU lock. > > Free removed stage-2 subtrees after an RCU grace period. To guarantee > all stage-2 table pages are freed before killing a VM, add an > rcu_barrier() to the flush path. > > Signed-off-by: Oliver Upton > --- > arch/arm64/kvm/mmu.c | 35 ++++++++++++++++++++++++++++++++++- > 1 file changed, 34 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 91521f4aab97..265951c05879 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -97,6 +97,38 @@ static void *stage2_memcache_zalloc_page(void *arg) > return kvm_mmu_memory_cache_alloc(mc); > } > > +#define STAGE2_PAGE_PRIVATE_LEVEL_MASK GENMASK_ULL(2, 0) > + > +static inline unsigned long stage2_page_private(u32 level, void *arg) > +{ > + unsigned long pvt = (unsigned long)arg; > + > + BUILD_BUG_ON(KVM_PGTABLE_MAX_LEVELS > STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + WARN_ON_ONCE(pvt & STAGE2_PAGE_PRIVATE_LEVEL_MASK); If the pgt pointer (arg) is not aligned for some reason, I think it might be better to BUG_ON(). Alternatively, why not trying to pass a new struct (with level and arg) that's freed by the rcu callback. > + > + return pvt | level; > +} > + > +static void stage2_free_removed_table_rcu_cb(struct rcu_head *head) > +{ > + struct page *page = container_of(head, struct page, rcu_head); > + unsigned long pvt = page_private(page); > + void *arg = (void *)(pvt & ~STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + u32 level = (u32)(pvt & STAGE2_PAGE_PRIVATE_LEVEL_MASK); > + void *pgtable = page_to_virt(page); > + > + kvm_pgtable_stage2_free_removed(pgtable, level, arg); > +} > + > +static void stage2_free_removed_table(void *pgtable, u32 level, void *arg) > +{ > + unsigned long pvt = stage2_page_private(level, arg); > + struct page *page = virt_to_page(pgtable); > + > + set_page_private(page, (unsigned long)pvt); > + call_rcu(&page->rcu_head, stage2_free_removed_table_rcu_cb); > +} > + > static void *kvm_host_zalloc_pages_exact(size_t size) > { > return alloc_pages_exact(size, GFP_KERNEL_ACCOUNT | __GFP_ZERO); > @@ -627,7 +659,7 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = { > .zalloc_page = stage2_memcache_zalloc_page, > .zalloc_pages_exact = kvm_host_zalloc_pages_exact, > .free_pages_exact = free_pages_exact, > - .free_removed_table = kvm_pgtable_stage2_free_removed, > + .free_removed_table = stage2_free_removed_table, > .get_page = kvm_host_get_page, > .put_page = kvm_host_put_page, > .page_count = kvm_host_page_count, > @@ -770,6 +802,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) > if (pgt) { > kvm_pgtable_stage2_destroy(pgt); > kfree(pgt); > + rcu_barrier(); > } > } > > -- > 2.37.2.672.g94769d06f0-goog >