From nobody Mon Oct 6 12:02:53 2025 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 6E31E2D3748 for ; Mon, 21 Jul 2025 18:01:10 +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=1753120871; cv=none; b=A5pkTQookQtzzNczkr2wPQ+6a1zc0E+DuWKwbI3vYUhWBxO6Xg6brljU36pUj3D56U9Dx8atQekGRReUZZ9ahnmQEMPI+LneyhMAuFSq+QuigIN4y2AqKXU2MUjSX6CIi3KAcu7LG6YaCXgT6acDyt0ig+mPe69mYEI0dtQKTII= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753120871; c=relaxed/simple; bh=pFi0iNg20dO512kniaVlxq0eQv3JXBjCcE9+ainODKU=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=LEWPqN3IYJ5DVFF4nk97x9ajR/qeNX9PtmwXXyefWjKFkw6/8helw0Er6r0yhkpY8Yd+qa2UuVh12SfRPr29x2rtfFIVhVfSRbgdhoW0AFjGp2OVPA21aUT+2hLgQITATrRNQcnmlrF+JAK5QpI5P3TnYSCLjBCQzFhgqx4LGXM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--brho.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=GBKxpzo4; 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--brho.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="GBKxpzo4" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-3132c1942a1so6216226a91.2 for ; Mon, 21 Jul 2025 11:01:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1753120870; x=1753725670; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=nkwILaoRvCGTt3850C+OpAJVMyb+bC6KByMj+ffuFyY=; b=GBKxpzo4jIZzmsmtFRmy4Ai2ztTkE98/cfShd+T5qQuDogeuTHR/0v/T8cuuvx7tXN pzXluF6ypAH2eIGEzMVPA8zw5LArsc6TwjRtMkb6FYgVHQ6YCGkexRtezOC2JgY4jzds GNrGI5OABDpr3XletwY2aHwiP7LISWu8uVkQBmyVmMmzfz+Us+GOSwVn7zkSTRnPmV6B sgWNpB+4r00Q0RXlSWBh2r9n80707UoYI9TDHlKf9p0Tzyf4EQwP/WQPrm1rj4+7WkVy J82EvENiGsMkKSXhRegPHV55Ceg0iMxSFrm0SPAZLN66X7ssLH2P7uaMiYb9PXbU6Bhm QfDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1753120870; x=1753725670; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=nkwILaoRvCGTt3850C+OpAJVMyb+bC6KByMj+ffuFyY=; b=fdC8xsr9X7X0WafjSPX+4vWUOn7m64zFCHQK3sk18Xm7u0yCVkyil5IuB6/Rg6DOuS ++9ikhQRXf3tEdq+CxOxX0vjibBC7+NuQCmRT2NzSDWz3fN9rRNtvv8kzE/k7fwbJIKc RZVbKX7G2MEnvKxlQFSu+RztL+Vf3F8lv+5c6qp/MTC4DrRyq2OFlA9D/dU9BbcJLNTA xMI9fq4nVoPHi1BeiJS4l8xdbeSEKmLLEwjWDPpBQG2o8JD7m5pfg75ozZGp+Tv6t2I6 DtWYy8EY38LJOfktae7wuzhGj4E50JLPU7CHAKxoJfE/Xb2z3BwAWc57GUrOljgIFn5w L55g== X-Forwarded-Encrypted: i=1; AJvYcCUfuHYO8DJWOUgcNKIdQNBFAlGxlc1RIIQCg7gFuEINULrocp2iuA6UbFqn5xiDsyXwQ2suIW4AUcayh8c=@vger.kernel.org X-Gm-Message-State: AOJu0YxqUkxoq6b627332RT5XiUrGE1prb/rDShXGee8I0TvOGsXaqte i2qg1DpHuSPAxGu/endYLPp9o2yJ87mrHhIh0AoGLzieg2ygxO4kaEt34/uDyEQ90UAiRLEPKw= = X-Google-Smtp-Source: AGHT+IEMVgugN4IL+CFFSpkR2FwGQ9XHs+U2c8+mJb7PyriwEGtvZrHfeHjlWf5Bk3t3+bv1LkyTurDn X-Received: from qkab26.prod.google.com ([2002:a05:620a:89a:b0:7e0:f93f:98db]) (user=brho job=prod-delivery.src-stubby-dispatcher) by 2002:a05:620a:4892:b0:7e3:54d8:3fdd with SMTP id af79cd13be357-7e354d84002mr1925664085a.16.1753120857996; Mon, 21 Jul 2025 11:00:57 -0700 (PDT) Date: Mon, 21 Jul 2025 18:00:47 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250721180051.3645697-1-brho@google.com> Subject: [PATCH] x86/resctrl: avoid divide by 0 num_rmid From: Barret Rhoden To: Tony Luck , Reinette Chatre Cc: Dave Martin , James Morse , linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" x86_cache_max_rmid's default is -1. If the hardware or VM doesn't set the right cpuid bits, num_rmid can be 0. Signed-off-by: Barret Rhoden --- I ran into this on a VM on granite rapids. I guess the VMM told the kernel it was a GNR, but didn't set all the cache/rsctl bits. arch/x86/kernel/cpu/resctrl/monitor.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/re= sctrl/monitor.c index c261558276cd..226dee05f96e 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -359,6 +359,12 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *= r) else if (mbm_offset > MBM_CNTR_WIDTH_OFFSET_MAX) pr_warn("Ignoring impossible MBM counter offset\n"); =20 + if (r->num_rmid < 1) { + pr_warn("Invalid num_rmid %d, cach_max_rmid was %d\n", + r->num_rmid, boot_cpu_data.x86_cache_max_rmid); + r->num_rmid =3D 1; + } + /* * A reasonable upper limit on the max threshold is the number * of lines tagged per RMID if all RMIDs have the same number of --=20 2.50.0.727.gbf7dc18ff4-goog