From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (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 32DA82557C for ; Thu, 4 Jan 2024 17:25:39 +0000 (UTC) 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="2VtJhetl" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-5cde2b113e7so420700a12.2 for ; Thu, 04 Jan 2024 09:25:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704389138; x=1704993938; darn=vger.kernel.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=OJb3XXC8q3g+6tXPhMxO+vJHUZX9WNbrN0ps04n6FVc=; b=2VtJhetlOet7TIeTKVMOu/WcJ2hgdoSNYeUyvNJJgoaG9Xu2zXzf8XGdTkzHa17LQC vmMzDUKs/EaUQh2Mx8U0DCZC2WlfD+mHsB8zA32/ERiz6uQ8DCYxzKXZnEjJYQnsp5rq amsvOhHLqW+/kfvxtFhZLdneCcT3r97B9JJYq4kCcOaKqZl70p2RiQxHK9uxLevKjTo5 /syEV+Z6sSWFirdpWERd5NiyIs0fhlqXGzC2bYCz3Ba9ppl8Bo9uE08cGClUoL02NDD3 ufOeNSmILCnmgdRzLZ0Nec0sfVtm6pG12ILkNr/ghjFUpy0R2VOXu0JmHFBQkCA26HfT XoGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704389138; x=1704993938; 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=OJb3XXC8q3g+6tXPhMxO+vJHUZX9WNbrN0ps04n6FVc=; b=VQj7smdqWNaUls9IiSKZ+YM+kkgak/f5G/ySj0HSNJ0ojbRHU/5bVefWsgyk1Cr6+W iAVrE26oXpabE3MPFc7MOIRTqZhwItIkquvKZ4fViOiKLeXW4y9/X4dDixZKpxU+GLfZ garu1E3/ffjiZLIfxAeqy50OSVuWB+ys/Tje0ld7OhPbVxg6t2NNsEN/JFEBF7awOqTF GmpiuL5S3GSEleBePfbrh2bwqraRayZDpfVzVEKtIbHIiyTSIByKp/79A/1fd01Np/zD jp94bfF6xE4YOsH8Y19V3G+NAQHpHBTE/bbwYTeez8238fJzLbXEI0etYJ2YtRui4/Tz qRCA== X-Gm-Message-State: AOJu0YwIfzc/DyVLlX4q9quCVvNs3SyRcRlWdJH0W/y+kfQJTghUd9IJ rPrWKM5IEyBabHiy4HQ61BmJytpRQ5iJ1sfd6Q== X-Google-Smtp-Source: AGHT+IGpjKYoYnovb4KpBjlwOvzKTsbKtS1OkjG+MYKimlevQSouppzqYOT0D/JiDpCYFh3Zij/ojr5FuiY= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a65:6a46:0:b0:5ce:a561:8868 with SMTP id o6-20020a656a46000000b005cea5618868mr6011pgu.4.1704389138519; Thu, 04 Jan 2024 09:25:38 -0800 (PST) Date: Thu, 4 Jan 2024 09:25:37 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <3d8f5987-e09c-4dd2-a9c0-8ba22c9e948a@paulmck-laptop> <88f49775-2b56-48cc-81b8-651a940b7d6b@paulmck-laptop> <77d7a3e3-f35e-4507-82c2-488405b25fa4@paulmck-laptop> Message-ID: Subject: Re: [BUG] Guest OSes die simultaneously (bisected) From: Sean Christopherson To: Paolo Bonzini Cc: paulmck@kernel.org, Like Xu , Andi Kleen , Kan Liang , Luwei Kang , Peter Zijlstra , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Breno Leitao , Arnaldo Carvalho de Melo , Ingo Molnar Content-Type: text/plain; charset="us-ascii" On Thu, Jan 04, 2024, Paolo Bonzini wrote: > On 1/4/24 17:06, Paul E. McKenney wrote: > > Instead, the point I am trying to make is that carefully > > constructed tests can serve as tireless and accurate code reviewers. > > This won't ever replace actual code review, but my experience indicates > > that it will help find more bugs more quickly and more easily. > > TBH this (conflict between virtual addresses on the host and the guest > leading to corruption of the guest) is probably not the kind of adversarial > test that one would have written or suggested right off the bat. I disagree. The flaws with PEBS using a virtual address is blatantly obvious to anyone that has spent any time dealing with the cross-section of PMU and VMX. Intel even explicitly added "isolation" functionality to ensure PEBS can't overrun VM-Enter and generate host records in the guest. Not to mention that Intel specifically addressed the virtual addressing issue in the design of Processor Trace (PT, a.k.a. RTIT). In other words, we *knew* exactly what would break *and* there had been breakage in the past. Chalk it up to messed up priorities, poor test infrastructure, or anything along those lines. But we shouldn't pretend that this was some obscure edge case that didn't warrant a dedicated test from the get-go.