From patchwork Tue Aug 30 19:51:01 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 12959819 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 CB56CECAAD5 for ; Tue, 30 Aug 2022 19:51:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231650AbiH3Tv2 (ORCPT ); Tue, 30 Aug 2022 15:51:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231522AbiH3TvX (ORCPT ); Tue, 30 Aug 2022 15:51:23 -0400 Received: from out2.migadu.com (out2.migadu.com [IPv6:2001:41d0:2:aacc::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8B8772B5E; Tue, 30 Aug 2022 12:51:21 -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=1661889080; 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=jyA52n5PXIfZG6yhWBQm3SaPH6T9tI0OWXKlc6krVCE=; b=LUuBibphlFTocfvHxEYwjPEhEbf34nsdxlCj+c68189duPaL4Z3ld/zR4FVqL4zRYfqU/c Ymt4M1PCH0aBBAwlq2co7SkEZPXrLewGCiTfKB4c5BIadgvKQ9jawXUG13aMoTW/tFH4no licZLjpIvirfUDEBqZ8h7/Mu/owfqH4= From: Oliver Upton To: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Catalin Marinas , Will Deacon Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Quentin Perret , Ricardo Koller , Reiji Watanabe , David Matlack , Ben Gardon , Paolo Bonzini , Gavin Shan , Peter Xu , Sean Christopherson , linux-kernel@vger.kernel.org Subject: [PATCH 11/14] KVM: arm64: Make changes block->table to leaf PTEs parallel-aware Date: Tue, 30 Aug 2022 19:51:01 +0000 Message-Id: <20220830195102.964724-1-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 In order to service stage-2 faults in parallel, stage-2 table walkers must take exclusive ownership of the PTE being worked on. An additional requirement of the architecture is that software must perform a 'break-before-make' operation when changing the block size used for mapping memory. Roll these two concepts together into helpers for performing a 'break-before-make' sequence. Use a special PTE value to indicate a PTE has been locked by a software walker. Additionally, use an atomic compare-exchange to 'break' the PTE when the stage-2 page tables are possibly shared with another software walker. Elide the DSB + TLBI if the evicted PTE was invalid (and thus not subject to break-before-make). All of the atomics do nothing for now, as the stage-2 walker isn't fully ready to perform parallel walks. Signed-off-by: Oliver Upton --- arch/arm64/kvm/hyp/pgtable.c | 87 +++++++++++++++++++++++++++++++++--- 1 file changed, 82 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 61a4437c8c16..71ae96608752 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -49,6 +49,12 @@ #define KVM_INVALID_PTE_OWNER_MASK GENMASK(9, 2) #define KVM_MAX_OWNER_ID 1 +/* + * Used to indicate a pte for which a 'break-before-make' sequence is in + * progress. + */ +#define KVM_INVALID_PTE_LOCKED BIT(10) + struct kvm_pgtable_walk_data { struct kvm_pgtable *pgt; struct kvm_pgtable_walker *walker; @@ -586,6 +592,8 @@ struct stage2_map_data { /* Force mappings to page granularity */ bool force_pte; + + bool shared; }; u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift) @@ -691,6 +699,11 @@ static bool stage2_pte_is_counted(kvm_pte_t pte) return kvm_pte_valid(pte) || kvm_invalid_pte_owner(pte); } +static bool stage2_pte_is_locked(kvm_pte_t pte) +{ + return !kvm_pte_valid(pte) && (pte & KVM_INVALID_PTE_LOCKED); +} + static bool stage2_try_set_pte(kvm_pte_t *ptep, kvm_pte_t old, kvm_pte_t new, bool shared) { if (!shared) { @@ -701,6 +714,69 @@ static bool stage2_try_set_pte(kvm_pte_t *ptep, kvm_pte_t old, kvm_pte_t new, bo return cmpxchg(ptep, old, new) == old; } +/** + * stage2_try_break_pte() - Invalidates a pte according to the + * 'break-before-make' requirements of the + * architecture. + * + * @ptep: Pointer to the pte to break + * @old: The previously observed value of the pte + * @addr: IPA corresponding to the pte + * @level: Table level of the pte + * @shared: true if the stage-2 page tables could be shared by multiple software + * walkers + * + * Returns: true if the pte was successfully broken. + * + * If the removed pte was valid, performs the necessary serialization and TLB + * invalidation for the old value. For counted ptes, drops the reference count + * on the containing table page. + */ +static bool stage2_try_break_pte(kvm_pte_t *ptep, kvm_pte_t old, u64 addr, u32 level, + struct stage2_map_data *data) +{ + struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops; + + if (stage2_pte_is_locked(old)) { + /* + * Should never occur if this walker has exclusive access to the + * page tables. + */ + WARN_ON(!data->shared); + return false; + } + + if (!stage2_try_set_pte(ptep, old, KVM_INVALID_PTE_LOCKED, data->shared)) + return false; + + /* + * Perform the appropriate TLB invalidation based on the evicted pte + * value (if any). + */ + if (kvm_pte_table(old, level)) + kvm_call_hyp(__kvm_tlb_flush_vmid, data->mmu); + else if (kvm_pte_valid(old)) + kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); + + if (stage2_pte_is_counted(old)) + mm_ops->put_page(ptep); + + return true; +} + +static void stage2_make_pte(kvm_pte_t *ptep, kvm_pte_t old, kvm_pte_t new, + struct stage2_map_data *data) +{ + struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops; + + WARN_ON(!stage2_pte_is_locked(*ptep)); + + if (stage2_pte_is_counted(new)) + mm_ops->get_page(ptep); + + smp_store_release(ptep, new); +} + static void stage2_put_pte(kvm_pte_t *ptep, struct kvm_s2_mmu *mmu, u64 addr, u32 level, struct kvm_pgtable_mm_ops *mm_ops) { @@ -836,17 +912,18 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, if (!childp) return -ENOMEM; + if (!stage2_try_break_pte(ptep, *old, addr, level, data)) { + mm_ops->put_page(childp); + return -EAGAIN; + } + /* * If we've run into an existing block mapping then replace it with * a table. Accesses beyond 'end' that fall within the new table * will be mapped lazily. */ - if (stage2_pte_is_counted(pte)) - stage2_put_pte(ptep, data->mmu, addr, level, mm_ops); - new = kvm_init_table_pte(childp, mm_ops); - mm_ops->get_page(ptep); - smp_store_release(ptep, new); + stage2_make_pte(ptep, *old, new, data); *old = new; return 0;