From patchwork Wed May 29 18:05:09 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Houghton X-Patchwork-Id: 13679436 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 7834AC25B7C for ; Wed, 29 May 2024 19:16:07 +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:Cc:To:From:Subject:Message-ID: References:Mime-Version:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=/nTRBxoV8JpdcaoKxrW0LLAvoSjOGThC/QTEf5uQm9s=; b=r94g+rdJWfQh+7Zq0LkMAsth6F 9L5J7wo/gI+NsOs0z1JfcArCZEpJQ7RJrx0ezQ8glvsg3vSUurpgMnPk0N6OeSRyWy8cczMxKU7AT hMjtv/FV2SlQ6xr3LenykfVViQBLGrAwQqWe3gJN/+m2xWEqW8LaIBHa9jUFoUG5VoKBus7qNZEuw uQ2jSmXi7ehuRJbBC8HghnIQ8O0bz6l4tm4RdDs/N8wg1DGf7h5aQVNOcJTSgl+U5yw/YV45F6ANC 4rgrUuZj5WpVUDYcQeJYfeNB4RuQqi4f8QzUb5xdFC0JSXvyam0OA4p7fatmybBRZ8w7hM+JKjjHK uRPlirGg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sCOmH-00000005JR5-2pZm; Wed, 29 May 2024 19:16:01 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sCNg3-000000058pP-1drW for linux-riscv@bombadil.infradead.org; Wed, 29 May 2024 18:05:31 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:Cc:To:From:Subject: Message-ID:References:Mime-Version:In-Reply-To:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=K/D/1FA4Uw1YrzG6+cN1+7larQcduYYAcSD+7tGLFpU=; b=SYucbSC0jVNTnj5dToxEUrBRjW n3EFgadIaJufTt9P6ZS7UJ9EXmix1EgoVm5t60we4wfOyntF7PLHvrib/fsqYeZ5KWtsumERz5n1g 4ZYSitTQ7e8L8UoGf07SsJiO2z8kJH3tohWRKtI5HCnj6IYZH8Xm2SDnTSjiBu74blnp8gE2j579N 8MHwCc1lnQ1SQ5BCiwaDcUe10Vh3yxjY+/v4OY/bHmrGtDXMQJNna5DRh53tAlaoemvTdevMac5te B+1ldLyILbE0R8CUxNLKfZmUG9vegxeN+NxqICJy4uGmYa9WXdvlQlXtGduH2GvdBreUr9J9wzAnP 8tN4aWww==; Received: from mail-yw1-x114a.google.com ([2607:f8b0:4864:20::114a]) by desiato.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sCNfw-0000000E1ol-3T6o for linux-riscv@lists.infradead.org; Wed, 29 May 2024 18:05:28 +0000 Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-627e9a500faso36958047b3.1 for ; Wed, 29 May 2024 11:05:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1717005923; x=1717610723; darn=lists.infradead.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=K/D/1FA4Uw1YrzG6+cN1+7larQcduYYAcSD+7tGLFpU=; b=H+XBvkUeg8sDezRU6S5ZIMZGpzQdoBOMC2MUFjLWT1TeCQhEH/bo4Lvj0pyqnYvhJX rWkYzWcXOfqcxmbIkjZh8bVd1fYMsdCud8OEQqrTYcgWGMlNqEyq9KnFQ9XJCReO4t+s AvPavWWckLcPHSri8kcVQfHDedaslGrOpf8BDj8tNbfrVeXiPJtd71384bfND6hGsmvM HSqlHVQAAr6mLm1GXWFl+kGjoeyssqHaJ65kkXr1/OeRhX+lbY+GWfy2l89ijig2vV2q 7fWZMFvZZ63WhL/z7c0ZkcspCbHJ/PGcPh57rJWzq/60MY0/YmPEeMtGHPpLw+9GS6Yl FiaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1717005923; x=1717610723; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=K/D/1FA4Uw1YrzG6+cN1+7larQcduYYAcSD+7tGLFpU=; b=apy3ae+AaaeCMbG5Ilw5UvC4BV9ZMQsnYMx4G5pL53KiMlFuy3DPFk0u/AUgADZDgo Ot8zz8dJKBU/P5wJvU3ZQmZr74HfDlFOEfK9DO5Kj68jvkcW2pRLQdIwncq2W3G1m0TB auc34tS1i3z2Ae+0/sNDsgWr1gkICQngQmCRP+GGxrrA/b5WU2mQvZcTFjD6TLOdtPLn RPrCaJDnnbFNEFdryM28Fd5Wb9PH7FWja+RfJP98GchNhflsh+ta8LIaTV9wZcGvUvh7 u+C40gxMaevWujcjRDIduM5hZZ7loXbnQ+7wMZsEaXetMYOzFfLnBwekXir2JtFsY+lJ Z2kw== X-Forwarded-Encrypted: i=1; AJvYcCXCU87N4QUJvF/IwsXeNv6U7++G0e/IUM0x6cjn2hZ1FN1Rncossi8nr6niDXmfA0f4xvh8AptOAck8YdoSVCF5EQfOYrA/bf79/ibCVlyB X-Gm-Message-State: AOJu0Yz3EkkivTAQ9iK63mw8kJ0KtyG/x+ME76wxO9BAOuRWHStqcsBF 83lNbSadVp1dZu1/MJ090Rl5xynwuOYhAZIu/t2ebjbRU1SkY2Qm4X6/WBFnOYvtLNShJWckTbW 1QjegH1likT2Ri6NM9g== X-Google-Smtp-Source: AGHT+IFSnjz7OFMOWeVI0MI1apHPovJ16H+bOSMdUdDO7KbUX1eLZ6QqkPj6sVplMDT0O6FTB3I8hMUTstLZ6+/c X-Received: from jthoughton.c.googlers.com ([fda3:e722:ac3:cc00:14:4d90:c0a8:2a4f]) (user=jthoughton job=sendgmr) by 2002:a05:690c:6010:b0:61a:e7f7:a4cc with SMTP id 00721157ae682-62a08dd7631mr39296497b3.4.1717005922981; Wed, 29 May 2024 11:05:22 -0700 (PDT) Date: Wed, 29 May 2024 18:05:09 +0000 In-Reply-To: <20240529180510.2295118-1-jthoughton@google.com> Mime-Version: 1.0 References: <20240529180510.2295118-1-jthoughton@google.com> X-Mailer: git-send-email 2.45.1.288.g0e0cd299f1-goog Message-ID: <20240529180510.2295118-7-jthoughton@google.com> Subject: [PATCH v4 6/7] KVM: arm64: Relax locking for kvm_test_age_gfn and kvm_age_gfn From: James Houghton To: Andrew Morton , Paolo Bonzini Cc: Albert Ou , Ankit Agrawal , Anup Patel , Atish Patra , Axel Rasmussen , Bibo Mao , Catalin Marinas , David Matlack , David Rientjes , Huacai Chen , James Houghton , James Morse , Jonathan Corbet , Marc Zyngier , Michael Ellerman , Nicholas Piggin , Oliver Upton , Palmer Dabbelt , Paul Walmsley , Raghavendra Rao Ananta , Ryan Roberts , Sean Christopherson , Shaoqin Huang , Shuah Khan , Suzuki K Poulose , Tianrui Zhao , Will Deacon , Yu Zhao , Zenghui Yu , kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240529_190525_033479_4422723E X-CRM114-Status: GOOD ( 14.97 ) X-BeenThere: linux-riscv@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-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Replace the MMU write locks for read locks. Grabbing the read lock instead of the write lock is safe because the only requirement we have is that the stage-2 page tables do not get deallocated while we are walking them. The stage2_age_walker() callback is safe to race with itself; update the comment to reflect the synchronization change. Signed-off-by: James Houghton --- arch/arm64/kvm/hyp/pgtable.c | 9 ++++----- arch/arm64/kvm/mmu.c | 8 ++++---- 2 files changed, 8 insertions(+), 9 deletions(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 9e2bbee77491..eabb07c66a07 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1319,10 +1319,8 @@ static int stage2_age_walker(const struct kvm_pgtable_visit_ctx *ctx, data->young = true; /* - * stage2_age_walker() is always called while holding the MMU lock for - * write, so this will always succeed. Nonetheless, this deliberately - * follows the race detection pattern of the other stage-2 walkers in - * case the locking mechanics of the MMU notifiers is ever changed. + * This walk may not be exclusive; the PTE is permitted to change + * from under us. */ if (data->mkold && !stage2_try_set_pte(ctx, new)) return -EAGAIN; @@ -1345,7 +1343,8 @@ bool kvm_pgtable_stage2_test_clear_young(struct kvm_pgtable *pgt, u64 addr, struct kvm_pgtable_walker walker = { .cb = stage2_age_walker, .arg = &data, - .flags = KVM_PGTABLE_WALK_LEAF, + .flags = KVM_PGTABLE_WALK_LEAF | + KVM_PGTABLE_WALK_SHARED, }; WARN_ON(kvm_pgtable_walk(pgt, addr, size, &walker)); diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 8337009dde77..40e7427462a7 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1775,7 +1775,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) u64 size = (range->end - range->start) << PAGE_SHIFT; bool young = false; - write_lock(&kvm->mmu_lock); + read_lock(&kvm->mmu_lock); if (!kvm->arch.mmu.pgt) goto out; @@ -1785,7 +1785,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) size, true); out: - write_unlock(&kvm->mmu_lock); + read_unlock(&kvm->mmu_lock); return young; } @@ -1794,7 +1794,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) u64 size = (range->end - range->start) << PAGE_SHIFT; bool young = false; - write_lock(&kvm->mmu_lock); + read_lock(&kvm->mmu_lock); if (!kvm->arch.mmu.pgt) goto out; @@ -1804,7 +1804,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) size, false); out: - write_unlock(&kvm->mmu_lock); + read_unlock(&kvm->mmu_lock); return young; }