From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42D11449B1F; Tue, 28 Jul 2026 14:31:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785249113; cv=none; b=UHLglGrMlCGr+YUhHOEMh4/8E/cba8fgTgyflV19go3jGB1emnFWwmkCQg+cs0GiZ8AuD0GQSDo32Rt06sD0PJpzmeMX8jp+55OkDkJSyawFq1nkvMGtRSLPtLh6BMRmin6hSoJJiUzKKAbyQ+snHLvcLGDQIGlEgsYBJURby08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785249113; c=relaxed/simple; bh=Xa1UbLLuDPNrmX++MKgqefbM0T9HGAdK0vw+TDjzPWw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Qoj0uGrjs27x9lMl4l6vevBhZ35k/qVts8E6IxgM7pT9B/mleGEzrGAxGTD0RLDHZPRfXQHSdc1TMjjZE3aklq+olwINeajTNUhxCx1Dtl0ntHt1unZQKDLcVWUusqDllAqJzgFJiMLoviJA7ltpitUPyZTsnSzXgkS3xCGUzwE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=uxw4gS+V; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="uxw4gS+V" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ylxLw5Zvv2evU7jmmQqp6rI9pLf6NLfhr20HsnCki9w=; b=uxw4gS+Vs58Hy3vhqrWgntua5G zQEksmEBJvslx0KRQxb0RXudR1WgcRb/xnnRwBS9xGVyxrjJGeybLRCAQaNQ2dnlvPhJrwVHHbcVP aIK3TfogFkt741WzhEPW1VMnaH/h6cWazMrko7O7Is8P/AAGyfKnIlMnjhiU6VY73iLk+FL2N1I/1 5kEFq2Ky7h7aC6sta8P2tAqPNWK8qYp7BOejIKZpNSWNWaoW43Yllxp1D45G/uS/IXIRKG2MfVbTA 8F2JdHUVQONJdBQ8/GetX+lhN8EW45KSVbsZma0nYiVdVzZs/zNk0okjdkVXKVz/DUC2iWV5znW7l Tm3+dgqA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1woiqG-0000000DS1h-3WHz; Tue, 28 Jul 2026 14:31:36 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id AF4A0300CDE; Tue, 28 Jul 2026 16:31:35 +0200 (CEST) Date: Tue, 28 Jul 2026 16:31:35 +0200 From: Peter Zijlstra To: Dave Hansen Cc: "Mike Rapoport (Microsoft)" , Dave Hansen , Andrew Morton , Andy Lutomirski , Borislav Petkov , David CARLIER , David Hildenbrand , Ingo Molnar , Jason Gunthorpe , Juergen Gross , Kevin Tian , Kiryl Shutsemau , "Liam R. Howlett" , Lorenzo Stoakes , Lu Baolu , "H. Peter Anvin" , Shakeel Butt , Suren Baghdasaryan , Thomas Gleixner , Toshi Kani , Vishal Moola , Vlastimil Babka , Will Deacon , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH 1/5] x86/mm/pat: introcude cpa_lock() and cpa_unlock() Message-ID: <20260728143135.GG651302@noisy.programming.kicks-ass.net> References: <20260728-cpa-fixes-v1-0-2ed2352300b3@kernel.org> <20260728-cpa-fixes-v1-1-2ed2352300b3@kernel.org> <20260728142108.GW751831@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jul 28, 2026 at 07:30:27AM -0700, Dave Hansen wrote: > On 7/28/26 07:21, Peter Zijlstra wrote: > > There was already a patch merged that removed the shole debug_pagealloc > > exception. Is that not better? > > As I'm scanning through email this morning, there's another issue that > popped up with that patch. It's causing hangs on boot. > > It's looking like debug pagealloc not taking the lock is actually > functional, not an optimization. Although, I hesitate to say > "functional" and would prefer to use much less nice words to describe it. Yeah, lets figure out why that is before we retain this wart ;-)