From patchwork Sat Dec 14 01:07:02 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13908234 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4CC5A1799F for ; Sat, 14 Dec 2024 01:07:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734138449; cv=none; b=Bd/JGNdngmleQztuxfvrdSPCn2lfi+Ka2Pd31vW6miQB9ApxV3bhQCwsT0u8Di4UELOhUouJpi3NkssgLNppM2mGHrSnjD0582b5EPp36kQboYvYsvqyIhR21pPUyoq7yOcQB0oFUk4TXLPQnFQ88rQT8VMb9bFspHjLP1CnLq8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734138449; c=relaxed/simple; bh=cSnwUK/2rXGD+rrAuQ2cWaSYdAoHz1OuzoU7A8Ugyzw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=GS4cYVPuKpYGtStww6ehj3RJOTgsAfNG6w3b8Hq7gsztqoYaTY0JFtGVUQln70ZiZCX7AS/yUeRB7nDPtrqJHtCbIUkKM1Ms1XDkoHdb99smKfo+hYu2QsT49tbmLAjYVL9O4fnzpAOcZPb2UuE7LND3R6JyZdwteXwV4JtdZY4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=p8Igj+q/; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="p8Igj+q/" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-2ef909597d9so3109441a91.3 for ; Fri, 13 Dec 2024 17:07:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1734138445; x=1734743245; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=FDkeem6MqewIEXRWoJcJJSDt8+RewhtQwmeUHyoVvwQ=; b=p8Igj+q/GB/05CyWdpM+D2gC13AKjgcSTCKkYZvIWWi0G1V97/D/g85yIgBFOAcpUU hxhHAoPvZRGA9JPz8QpFBerjqDtVzZyxYV4sgZaGKu+wZ2qHAQJXzRY/JX/LH8Su0+2+ O9A49qfvmxZa0jK/KCh6GFSlVEUB51l0+ojpmJxzD2NPt61dptpZwff0wKpQS7FQS/L0 hZgDuY6xJzJP4KgSwuIBeajitheja8I+uhZmzdmMq5B7Vr0GRi5a4MkPjHdw3iA4n1FR VE+XRxO0Z43SB0WepodwIrUu4oOFKhexTLAlN33ahyvdv1sM21CajGimX9DqHg7912Ov Xaqg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1734138445; x=1734743245; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=FDkeem6MqewIEXRWoJcJJSDt8+RewhtQwmeUHyoVvwQ=; b=slVy5P0ZVV/YQh1ZHBsO/rcImBmRrHDvkQoaEBeU2RiauN8k3644wohsnIrl5a3Gme sJr9UI9RLReY/HG8F/ju3/7HGnWxIYflXCm228TVBBwtjcdK6PVBxsxj7X13U5U/ysM4 dVxD6uwOWCRQZC2F7K5IbaVJI8M6fCvSzOLkBqF5Xz1d8wRFdtICOfCqP1fyGwU6wYKi b7NhJWvmy7U1OeGhlzjp84940tMmuowDxk7vYbaIX5/SMIh8eNp9PqDdJfiB4aA7VrWb F6XC7bR1F5p8duhqxoT2pkTDaECiEDhrCZDJPkQLjRvVrybh/NWQiuViKUn1cnVi1NL3 4vKA== X-Gm-Message-State: AOJu0YzEastKXlGR8H9MgwI8yTRSRne/v9A623sYMidQoq2Pe14mUnFW FsgChVpiV8fTOG495X9N3mo/SM0geUvfLZZqhB2XaQVlmQbsTZsYvPX2VsdjauVfaQakTVqnjnw tyw== X-Google-Smtp-Source: AGHT+IFK32cTaqoqTJNazGtX5TzExs7AH57kjcR5A7Qc6S14R9Qqh2LtvZ+1ec7OP+laMIvBdbl42YkuaIU= X-Received: from pjf15.prod.google.com ([2002:a17:90b:3f0f:b0:2ea:aa56:49c]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:d450:b0:2ee:d024:e4fc with SMTP id 98e67ed59e1d1-2f2901b3661mr7398519a91.33.1734138445502; Fri, 13 Dec 2024 17:07:25 -0800 (PST) Reply-To: Sean Christopherson Date: Fri, 13 Dec 2024 17:07:02 -0800 In-Reply-To: <20241214010721.2356923-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241214010721.2356923-1-seanjc@google.com> X-Mailer: git-send-email 2.47.1.613.gc27f4b7a9f-goog Message-ID: <20241214010721.2356923-2-seanjc@google.com> Subject: [PATCH 01/20] KVM: selftests: Support multiple write retires in dirty_log_test From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Xu , Maxim Levitsky , Sean Christopherson From: Maxim Levitsky If dirty_log_test is run nested, it is possible for entries in the emulated PML log to appear before the actual memory write is committed to the RAM, due to the way KVM retries memory writes as a response to a MMU fault. In addition to that in some very rare cases retry can happen more than once, which will lead to the test failure because once the write is finally committed it may have a very outdated iteration value. Detect and avoid this case. Cc: Peter Xu Signed-off-by: Maxim Levitsky Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/dirty_log_test.c | 52 +++++++++++++++++++- 1 file changed, 50 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c index aacf80f57439..cdae103314fc 100644 --- a/tools/testing/selftests/kvm/dirty_log_test.c +++ b/tools/testing/selftests/kvm/dirty_log_test.c @@ -152,6 +152,7 @@ static atomic_t vcpu_sync_stop_requested; * sem_vcpu_stop and before vcpu continues to run. */ static bool dirty_ring_vcpu_ring_full; + /* * This is only used for verifying the dirty pages. Dirty ring has a very * tricky case when the ring just got full, kvm will do userspace exit due to @@ -166,7 +167,51 @@ static bool dirty_ring_vcpu_ring_full; * dirty gfn we've collected, so that if a mismatch of data found later in the * verifying process, we let it pass. */ -static uint64_t dirty_ring_last_page; +static uint64_t dirty_ring_last_page = -1ULL; + +/* + * In addition to the above, it is possible (especially if this + * test is run nested) for the above scenario to repeat multiple times: + * + * The following can happen: + * + * - L1 vCPU: Memory write is logged to PML but not committed. + * + * - L1 test thread: Ignores the write because its last dirty ring entry + * Resets the dirty ring which: + * - Resets the A/D bits in EPT + * - Issues tlb flush (invept), which is intercepted by L0 + * + * - L0: frees the whole nested ept mmu root as the response to invept, + * and thus ensures that when memory write is retried, it will fault again + * + * - L1 vCPU: Same memory write is logged to the PML but not committed again. + * + * - L1 test thread: Ignores the write because its last dirty ring entry (again) + * Resets the dirty ring which: + * - Resets the A/D bits in EPT (again) + * - Issues tlb flush (again) which is intercepted by L0 + * + * ... + * + * N times + * + * - L1 vCPU: Memory write is logged in the PML and then committed. + * Lots of other memory writes are logged and committed. + * ... + * + * - L1 test thread: Sees the memory write along with other memory writes + * in the dirty ring, and since the write is usually not + * the last entry in the dirty-ring and has a very outdated + * iteration, the test fails. + * + * + * Note that this is only possible when the write was the last log entry + * write during iteration N-1, thus remember last iteration last log entry + * and also don't fail when it is reported in the next iteration, together with + * an outdated iteration count. + */ +static uint64_t dirty_ring_prev_iteration_last_page; enum log_mode_t { /* Only use KVM_GET_DIRTY_LOG for logging */ @@ -316,6 +361,8 @@ static uint32_t dirty_ring_collect_one(struct kvm_dirty_gfn *dirty_gfns, struct kvm_dirty_gfn *cur; uint32_t count = 0; + dirty_ring_prev_iteration_last_page = dirty_ring_last_page; + while (true) { cur = &dirty_gfns[*fetch_index % test_dirty_ring_count]; if (!dirty_gfn_is_dirtied(cur)) @@ -613,7 +660,8 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap) */ min_iter = iteration - 1; continue; - } else if (page == dirty_ring_last_page) { + } else if (page == dirty_ring_last_page || + page == dirty_ring_prev_iteration_last_page) { /* * Please refer to comments in * dirty_ring_last_page.