From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta0.migadu.com (out-176.mta0.migadu.com [91.218.175.176]) (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 CE72E2DF84 for ; Tue, 2 Apr 2024 07:00:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712041236; cv=none; b=YBLUvLaidfVwLjw1PX2hp1rjy5B/88pc1sgdQ2mD6dHNJrClx15GOb5TSuQzY9T0E1f4XoDd+RE0pef8sddYH2pUkzWzkTu20pHQ8FjsuAI7kkPpm8EiUqk08StK/a5HEwhYsiokLdkegeTmdptDMJ2eu16boCTCvqKCQ+1BTh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712041236; c=relaxed/simple; bh=DWwpz4wCjpd3OHwoJNho95qF247VTvrYLLaNHUDRIQs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IgMPrhEkk7d8U//zGniJQw5g1DP2406iYI5BIAek4UaBOq4klxAA5n1V1slFSh39qw1qAh+V1c4BHkueH6X+LXwtwdZ6Rr7Dr+2Uf0UMmCH8T/ZaE38ZdbjvD1JEgYPBz14hZvQW+vnl7Rc9ICwmkWp3OszZW5OsBwtEdt9L0GY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=KgJN+PKw; arc=none smtp.client-ip=91.218.175.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="KgJN+PKw" Date: Tue, 2 Apr 2024 00:00:12 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1712041232; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jhuzyWXDmRkSGaUwWTpdDkWh7n7iwav7be8n1ReoOqg=; b=KgJN+PKwUf4lvMCNNgRHnuy8Gq613K2HNrcIC+CQUk8Sf/7s4Hx+E56N6lZRoCSA0Dlm9q gxlbMuDbSrzUHZgC90oQuyB0Kd8gPYgsVUsYB6BOdjK0DzwQ2E0WmDAtMn29DrZYMJC+lr +c9QBLLVlmBOcBZkzESUyH9WEo8wfW4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Yu Zhao Cc: James Houghton , Andrew Morton , Paolo Bonzini , David Matlack , Marc Zyngier , Sean Christopherson , Jonathan Corbet , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shaoqin Huang , Gavin Shan , Ricardo Koller , Raghavendra Rao Ananta , Ryan Roberts , David Rientjes , Axel Rasmussen , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 6/7] KVM: arm64: Participate in bitmap-based PTE aging Message-ID: References: <20240401232946.1837665-1-jthoughton@google.com> <20240401232946.1837665-7-jthoughton@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT On Tue, Apr 02, 2024 at 12:06:56AM -0400, Yu Zhao wrote: > On Mon, Apr 1, 2024 at 7:30 PM James Houghton wrote: > > Suggested-by: Yu Zhao > > Thanks but I did not suggest this. Entirely up to you, but I would still want to credit everyone who contributed to a feature even if the underlying implementation has changed since the original attempt. > What I have in v2 is RCU based. I hope Oliver or someone else can help > make that work. Why? If there's data to show that RCU has a material benefit over taking the MMU lock for read then I'm all for it. Otherwise, the work required to support page-table walkers entirely outside of the MMU lock isn't justified. In addition to ensuring that page table teardown is always RCU-safe, we'd need to make sure all of the walkers that take the write lock are prepared to handle races. > Otherwise we can just drop this for now and revisit > later. I really wouldn't get hung up on the locking as the make-or-break for whether arm64 supports this MMU notifier. -- Thanks, Oliver From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B68C1C6FD1F for ; Tue, 2 Apr 2024 07:00:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=2tft3UuIh1kNZWuwVyyrNBf0EM3WNot6JVSTui2YmUo=; b=qdeHSaperExubF 9dK4xf71u2viXE+aQWOyrYGbM5+SQv1cNthbDha8L7SBECCz0b2AMQK1XbeeMf47SrPUW9zl1NEgT BDZ+ixHgUOsjaPCt14Gd8VrXhmrEkF8WKgL+a9whpWZFHAim7iYEQ5JnCgi6wTgqWSqBUTdE1Cr06 mepOX4XAH4OvBz42cnWinEkjWHF+hNggTWnxoINKEOTzaCQ3vWilpepFJf7a0RtPc0clKppnjXiG5 Mg75y47b3b3elEzNktEhdub5awD0iw2w46cBnPcan9eWqrbC5b4W20WYuHgo3g8GDBcUxwRuuWsjp 1KtqlavyegosDXVVbgug==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rrY8O-00000009zvs-2aX7; Tue, 02 Apr 2024 07:00:40 +0000 Received: from out-177.mta0.migadu.com ([2001:41d0:1004:224b::b1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rrY8L-00000009zti-04Bp for linux-arm-kernel@lists.infradead.org; Tue, 02 Apr 2024 07:00:38 +0000 Date: Tue, 2 Apr 2024 00:00:12 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1712041232; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jhuzyWXDmRkSGaUwWTpdDkWh7n7iwav7be8n1ReoOqg=; b=KgJN+PKwUf4lvMCNNgRHnuy8Gq613K2HNrcIC+CQUk8Sf/7s4Hx+E56N6lZRoCSA0Dlm9q gxlbMuDbSrzUHZgC90oQuyB0Kd8gPYgsVUsYB6BOdjK0DzwQ2E0WmDAtMn29DrZYMJC+lr +c9QBLLVlmBOcBZkzESUyH9WEo8wfW4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Yu Zhao Cc: James Houghton , Andrew Morton , Paolo Bonzini , David Matlack , Marc Zyngier , Sean Christopherson , Jonathan Corbet , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shaoqin Huang , Gavin Shan , Ricardo Koller , Raghavendra Rao Ananta , Ryan Roberts , David Rientjes , Axel Rasmussen , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 6/7] KVM: arm64: Participate in bitmap-based PTE aging Message-ID: References: <20240401232946.1837665-1-jthoughton@google.com> <20240401232946.1837665-7-jthoughton@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240402_000037_282490_3B44B81E X-CRM114-Status: GOOD ( 13.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVHVlLCBBcHIgMDIsIDIwMjQgYXQgMTI6MDY6NTZBTSAtMDQwMCwgWXUgWmhhbyB3cm90ZToK PiBPbiBNb24sIEFwciAxLCAyMDI0IGF0IDc6MzDigK9QTSBKYW1lcyBIb3VnaHRvbiA8anRob3Vn aHRvbkBnb29nbGUuY29tPiB3cm90ZToKPiA+IFN1Z2dlc3RlZC1ieTogWXUgWmhhbyA8eXV6aGFv QGdvb2dsZS5jb20+Cj4gCj4gVGhhbmtzIGJ1dCBJIGRpZCBub3Qgc3VnZ2VzdCB0aGlzLgoKRW50 aXJlbHkgdXAgdG8geW91LCBidXQgSSB3b3VsZCBzdGlsbCB3YW50IHRvIGNyZWRpdCBldmVyeW9u ZSB3aG8KY29udHJpYnV0ZWQgdG8gYSBmZWF0dXJlIGV2ZW4gaWYgdGhlIHVuZGVybHlpbmcgaW1w bGVtZW50YXRpb24gaGFzCmNoYW5nZWQgc2luY2UgdGhlIG9yaWdpbmFsIGF0dGVtcHQuCgo+IFdo YXQgSSBoYXZlIGluIHYyIGlzIFJDVSBiYXNlZC4gSSBob3BlIE9saXZlciBvciBzb21lb25lIGVs c2UgY2FuIGhlbHAKPiBtYWtlIHRoYXQgd29yay4KCldoeT8gSWYgdGhlcmUncyBkYXRhIHRvIHNo b3cgdGhhdCBSQ1UgaGFzIGEgbWF0ZXJpYWwgYmVuZWZpdCBvdmVyIHRha2luZwp0aGUgTU1VIGxv Y2sgZm9yIHJlYWQgdGhlbiBJJ20gYWxsIGZvciBpdC4gT3RoZXJ3aXNlLCB0aGUgd29yayByZXF1 aXJlZAp0byBzdXBwb3J0IHBhZ2UtdGFibGUgd2Fsa2VycyBlbnRpcmVseSBvdXRzaWRlIG9mIHRo ZSBNTVUgbG9jayBpc24ndApqdXN0aWZpZWQuCgpJbiBhZGRpdGlvbiB0byBlbnN1cmluZyB0aGF0 IHBhZ2UgdGFibGUgdGVhcmRvd24gaXMgYWx3YXlzIFJDVS1zYWZlLAp3ZSdkIG5lZWQgdG8gbWFr ZSBzdXJlIGFsbCBvZiB0aGUgd2Fsa2VycyB0aGF0IHRha2UgdGhlIHdyaXRlIGxvY2sgYXJlCnBy ZXBhcmVkIHRvIGhhbmRsZSByYWNlcy4KCj4gT3RoZXJ3aXNlIHdlIGNhbiBqdXN0IGRyb3AgdGhp cyBmb3Igbm93IGFuZCByZXZpc2l0Cj4gbGF0ZXIuCgpJIHJlYWxseSB3b3VsZG4ndCBnZXQgaHVu ZyB1cCBvbiB0aGUgbG9ja2luZyBhcyB0aGUgbWFrZS1vci1icmVhayBmb3IKd2hldGhlciBhcm02 NCBzdXBwb3J0cyB0aGlzIE1NVSBub3RpZmllci4KCi0tIApUaGFua3MsCk9saXZlcgoKX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KbGludXgtYXJtLWtlcm5l bCBtYWlsaW5nIGxpc3QKbGludXgtYXJtLWtlcm5lbEBsaXN0cy5pbmZyYWRlYWQub3JnCmh0dHA6 Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgtYXJtLWtlcm5lbAo=