From patchwork Mon Nov 7 21:58:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 13035354 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 943C1C4332F for ; Mon, 7 Nov 2022 22:01:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Z8kjYe+akQQs0Flow3lc7JpsN5FMg3O85rC5S9T2NeI=; b=DJZu7W5BvGHMCB zJnuSiXhRWe032xrwApm5wmBnFCurHZYHeUfKgCXTg3GQzYImJCxSInOUvgCGhe5p1RlCeohnaAfM UTtiwUOI5H6DnMvj9kUmVJPhRFozbTZDIq90zEy8eKW669iFjiUMHhFkikd90WB+vqLhGlw8UXGUZ Xip8+AU+2kfEzdlfRAZhW/cdUfscVlyvqcO3DApoQlpjQIFf6NMrBIBD+nqFTItF6PpRxoQ3Nf64l KMozwn5NEK/UkQHKBdnf+/ON96+mDylJeixuQLjF2soBgsoxzsbkOHRX10Rq3kJQDIKpMm6HZkIG+ IZ+ALVT1sWdy908G6VAA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1osAAP-000rJZ-4i; Mon, 07 Nov 2022 22:00:29 +0000 Received: from out2.migadu.com ([188.165.223.204]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1osA9F-000qcT-VC for linux-arm-kernel@lists.infradead.org; Mon, 07 Nov 2022 21:59:19 +0000 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=1667858345; 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=Wjq4QDt9xZJvVi5eTYg9PIR4fiNZZIcRNu978aLl+WU=; b=qlHqiut8sI1vgbFWY9FSD2/2a16CyuAbQeA3uuU451g2i3xwblSgrH+EwM2o5+2i2A0AB6 yhJj6DoLWjl8fbIbMIMQyIj812LambgYU75iuQ5zMrgqNsYFewtzJjQo/nqxX8aT2xL7dy tu5OPjHn6rOJbipMkSGD1vkcJVqso30= From: Oliver Upton To: Marc Zyngier , James Morse , Alexandru Elisei Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Reiji Watanabe , Ricardo Koller , David Matlack , Quentin Perret , Ben Gardon , Gavin Shan , Peter Xu , Will Deacon , Sean Christopherson , kvmarm@lists.linux.dev, Oliver Upton Subject: [PATCH v5 11/14] KVM: arm64: Make block->table PTE changes parallel-aware Date: Mon, 7 Nov 2022 21:58:55 +0000 Message-Id: <20221107215855.1895367-1-oliver.upton@linux.dev> In-Reply-To: <20221107215644.1895162-1-oliver.upton@linux.dev> References: <20221107215644.1895162-1-oliver.upton@linux.dev> MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221107_135918_322053_8C8CD2AE X-CRM114-Status: GOOD ( 17.61 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 | 80 +++++++++++++++++++++++++++++++++--- 1 file changed, 75 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index f4dd77c6c97d..b9f0d792b8d9 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_walker *walker; @@ -674,6 +680,11 @@ static bool stage2_pte_is_counted(kvm_pte_t pte) return !!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(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t new) { if (!kvm_pgtable_walk_shared(ctx)) { @@ -684,6 +695,64 @@ static bool stage2_try_set_pte(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_ return cmpxchg(ctx->ptep, ctx->old, new) == ctx->old; } +/** + * stage2_try_break_pte() - Invalidates a pte according to the + * 'break-before-make' requirements of the + * architecture. + * + * @ctx: context of the visited pte. + * @mmu: stage-2 mmu + * + * 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(const struct kvm_pgtable_visit_ctx *ctx, + struct kvm_s2_mmu *mmu) +{ + struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; + + if (stage2_pte_is_locked(ctx->old)) { + /* + * Should never occur if this walker has exclusive access to the + * page tables. + */ + WARN_ON(!kvm_pgtable_walk_shared(ctx)); + return false; + } + + if (!stage2_try_set_pte(ctx, KVM_INVALID_PTE_LOCKED)) + return false; + + /* + * Perform the appropriate TLB invalidation based on the evicted pte + * value (if any). + */ + if (kvm_pte_table(ctx->old, ctx->level)) + kvm_call_hyp(__kvm_tlb_flush_vmid, mmu); + else if (kvm_pte_valid(ctx->old)) + kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, ctx->addr, ctx->level); + + if (stage2_pte_is_counted(ctx->old)) + mm_ops->put_page(ctx->ptep); + + return true; +} + +static void stage2_make_pte(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t new) +{ + struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; + + WARN_ON(!stage2_pte_is_locked(*ctx->ptep)); + + if (stage2_pte_is_counted(new)) + mm_ops->get_page(ctx->ptep); + + smp_store_release(ctx->ptep, new); +} + static void stage2_put_pte(const struct kvm_pgtable_visit_ctx *ctx, struct kvm_s2_mmu *mmu, struct kvm_pgtable_mm_ops *mm_ops) { @@ -812,17 +881,18 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx, if (!childp) return -ENOMEM; + if (!stage2_try_break_pte(ctx, data->mmu)) { + 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(ctx->old)) - stage2_put_pte(ctx, data->mmu, mm_ops); - new = kvm_init_table_pte(childp, mm_ops); - mm_ops->get_page(ctx->ptep); - smp_store_release(ctx->ptep, new); + stage2_make_pte(ctx, new); return 0; }