From patchwork Tue Aug 30 19:41:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 12959815 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 47753ECAAD5 for ; Tue, 30 Aug 2022 19:43:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231403AbiH3Tm6 (ORCPT ); Tue, 30 Aug 2022 15:42:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231310AbiH3Tmk (ORCPT ); Tue, 30 Aug 2022 15:42:40 -0400 Received: from out1.migadu.com (out1.migadu.com [IPv6:2001:41d0:2:863f::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F3EF57C753; Tue, 30 Aug 2022 12:42:27 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1661888545; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NFwSFftgtou/xmW0mHXjm84oZeXHuVM1GyZ5T83/2Wg=; b=uI1s1ijlRaMGjo0jD+nYZDxRHNF+xtPjYfu05N6LNtXIkm3dIie5gtYAIPsiOyuJ6ClfhV ybPxb7Q1Jo+wBTKNu8gdTSY/P1/46syt8d1oBiKjfi4BdrV1c4EXFGM6kN02too/RLt5YY AYtX+JXtuvSVgqwwikvtaPajlrG+7rA= From: Oliver Upton To: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , Will Deacon , Quentin Perret , Ricardo Koller , Reiji Watanabe , David Matlack , Ben Gardon , Paolo Bonzini , Gavin Shan , Peter Xu , Sean Christopherson , Oliver Upton Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 09/14] KVM: arm64: Free removed stage-2 tables in RCU callback Date: Tue, 30 Aug 2022 19:41:27 +0000 Message-Id: <20220830194132.962932-10-oliver.upton@linux.dev> In-Reply-To: <20220830194132.962932-1-oliver.upton@linux.dev> References: <20220830194132.962932-1-oliver.upton@linux.dev> MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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); + + 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(); } }