From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.214.199 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793041187; b=di1DdTwwW2x9v9313oHURNfn897RDzuhplSWEY8NvaF8wa0e+7cUpjA4bDT/LzIAbQgw pj8dmEjfTyJlyPNf/cj83kiUIWBREnAFCGff0w/futE1sh4bssvO8e5BAd3A8sTEla852 6sWosFchCEQb9LdQQpZChfBwyA+5wqBZTSgza6WL+p9GNd5pD2EtBSduLE9R0kPdShJHs V3sK6aMsFHb/NFNcOvuIfLy1jpHFAdrMU8VRYwba01uFJ9IupR70zNeAn6818d2Xt1lLl DTISRVKoWNOT92WsqdUW2i/AuUKpVuGibtQuWNxBcdbdnBz+lGLXrmZv8xmRkJo2orw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793041187; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Received:Date:In-Reply-To: Mime-Version:References:Message-ID:Subject:From:To:Cc:Content-Type: Content-Transfer-Encoding; bh=vFQSzrzMPbR886MkQnFhhUgLb0bB/SvZ7Bv3piD6vcA=; b=YnIoqrjHlQPAxdP5dJNr37KntYQZfWUlTiL06vzuKcHG3Kovgt1Tl/K98CntE4j6PCsy aMR2tx+ksQde29w0eaZTfFQxRZQ0fbzJhGtrb+8lAjphNv8PoyAk9rRTY9oGJbl9J7PUy wSQDmd7msypo5asWGrIQTAvA/Kg3Vq9sFZnFRmqdU6f1Tl/eoH5vG/O1r55alNpYo+fEt noighJsgxzhK7xWz5j3fzUgepCOPNvW5HDktFSZJdAqAB7BHA571w3HczlQMhYDQjQo1X YI3CZIRowUXkUgSJ/WNy6u6r55qGifUIhp7mGVcfzy0X3PkX72c/5181hvUFhFZ7rJQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20251104 header.b=NUlN30vn; arc=none smtp.remote-ip=209.85.214.199 Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D973F606A31A for ; Mon, 26 Oct 2026 18:59:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org D973F606A31A 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, unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20251104 header.b=NUlN30vn Received: by mail-pl1-f199.google.com with SMTP id d9443c01a7336-2e9821ca96fso38594385ad.0 for ; Mon, 26 Oct 2026 11:59:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1793041186; x=1793645986; darn=vger.kernel.org; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date:from:to:cc :subject:date:message-id:reply-to:content-type; bh=vFQSzrzMPbR886MkQnFhhUgLb0bB/SvZ7Bv3piD6vcA=; b=NUlN30vnYiu/NIUtOUp+Tn4OxP3vIq7NpWCK/SBMEp0pzsRPLp3PSYWwv08HqWKq8c DMP+nLjVSEnuniHsAymIsTM7kpVYCHa534FAc0ZvmNh2LQP7iDWqKwIMJi38LGZTGDai UeOiaWkYNaKU5kKenhqjQOe59hKsMNOukDtG7z9etMGVjBwVzOIm2DDtSAHyuyna1r9N EKQ1ZW4a6Riu45WU8/INkcUq3hRDjnw6Gx3WDw/Nh/Zpx823xFlqRzTueV/kpLJei9sQ SJHpd3BuAkucBYeUwPkuvYyabt7yBtr8wYdd4gZisVFmGSmVfgbzBj7zOlsMc38qTUyo Ts0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793041186; x=1793645986; h=content-transfer-encoding:content-type: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 :content-type; bh=vFQSzrzMPbR886MkQnFhhUgLb0bB/SvZ7Bv3piD6vcA=; b=GQoO/2ZKFIYh/QxGxDcyDzck0+krHcDZV5WmihEZuSXrOH0RQPSvDKD6PMoVmetq1X MvA0/hft9BtIl95Rn+6rW6Vso/0adxJQ65Z11UVyrf1T+m+ZIuI/M+1+K6UQ6mmYGmAw GBN37ufSmyd8pAbY7e9bFHs7ZiSW35f3c+SW+rwfeukODsG/0JGI6Wm3l3Dw76PgiIS9 FBYHXA/cGxlfIFOzIEO3+ehoYrgnD7Xjr+FW2fqRr4xmyKAZmd0JzzuQxnSNekGpauMp BdsJPUkd0Upj5lvWEDEOtgioulrl/9g4Sch3q1z1M4VZ0r8GtHHLvERgFoWDp2wCB/lo AvUg== X-Forwarded-Encrypted: i=1; AKwUvBxVQsgylWScpqrUoBrOtendZM0u2iUVAiRi8CxO7saJvkWSo2F2qnDcljRgW3e81xBlQQs=@vger.kernel.org X-Gm-Message-State: AFq9FYIs0g6OwdUFWzgrU8XN24GuKBIfO/sJGVZQI0kK0KRdd8DKDIr2 cKEMnl/Qj0uKq5qamuIJqp5yUVANuaBwQYULT/8cZ4bbDtz6NfCz83Ce2O6RkoxBMZAtdBb/ix+ 3pYmXPg== X-Received: from ploe5.prod.google.com ([2002:a17:903:2405:b0:2df:a429:6698]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:3805:b0:2e9:460e:ca57 with SMTP id d9443c01a7336-2ea9c66910dmr71815065ad.15.1793041186062; Mon, 26 Oct 2026 11:59:46 -0700 (PDT) Date: Mon, 26 Oct 2026 11:59:45 -0700 In-Reply-To: X-Mailing-List: kvm@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 References: <20261022215541.631694-1-seanjc@google.com> Message-ID: Subject: Re: [PATCH 0/2] KVM: x86: Convert all runtime WARNs to ONCE From: Sean Christopherson To: Vitaly Kuznetsov Cc: Yosry Ahmed , Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Teodorescu Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Mon, Oct 26, 2026, Vitaly Kuznetsov wrote: > Yosry Ahmed writes: >=20 > > On Mon, Oct 26, 2026 at 10:36=E2=80=AFAM Sean Christopherson wrote: > >> > >> On Fri, Oct 23, 2026, Yosry Ahmed wrote: > >> > On Thu, Oct 22, 2026 at 2:55=E2=80=AFPM Sean Christopherson wrote: > >> > > > >> > > Convert all bare WARN() and WARN_ON() runtime usage, i.e. WARNs th= at aren't > >> > > strictly scoped to module init/exit, or similar, to ONCE() variant= s for what > >> > > should be fairly obvious reasons at this point. > >> > > >> > Do you wanna CC stable? > >> > >> Not really? Maybe? I worry that this will generate an absurd number = of conflicts > >> and also have "misses" in older kernels, to the point where it oculd d= o more harm > >> than good. > >> > >> I could be convinced this should be tagged for stable@, though honestl= y it might > >> be better to omit the automatic backport trigger and just rely on some= one to > >> "manually" provide equivalent patches. > > > > I can just see this ultimately preventing a DoS and if it lands on any > > stable kernel it should be a win, but yeah probably manual backports > > are needed :/ >=20 > With my backporter's hat on, it would help significantly if we split the > patch per-area (hyperv, [l]apic, posted_intr, vmx, svm,...). It would > also help those who want to analyze whether the particular WARN_ON() is > actually guest triggerable and open the corresponding CVEs. Honestly, I don't think that's actually going to help. Exactly which WARNs= are problematic will vary by kernel, a lot. I.e. the set of WARNs that are spa= mmable *now* is not the same set that was spammable in 6.18, 6.12, 6.6, 6.1, etc. = Then factor in different configurations and threat models, and the set of proble= matic WARNs gets quite large. So from an upstream perspective, I think we should assume everything the wo= rst and "fix" everything, and then do the same for LTS kernels. I.e. backport = the concept of "never do multi-WARNs at runtime", not necessarily the literal p= atch.