From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from flow-b3-smtp.messagingengine.com (flow-b3-smtp.messagingengine.com [202.12.124.138]) (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 B40FD1DD525; Mon, 10 Mar 2025 21:21:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=202.12.124.138 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741641670; cv=none; b=Ca8pQYcM3Rcy9U27Gs19Xz7c2Vgff/ACtWj3QI/RUsBDyTRquUNSTtXVsFh+MKeWl/iJHTOe5qTDQjLXuSeAnDcGgtROOre3WS8pehgO2/ZEvt4iBaspsvJ17RRRqO2PfBSRtTseRmdh5+Fl0VLYo8K28RKO5C9NcvEe4ZcwwDI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741641670; c=relaxed/simple; bh=b+pL5tPz/STvzduyR8tAJGIpWCTLY7xMzNfVgLy+oho=; h=MIME-Version:Date:From:To:Cc:Message-Id:In-Reply-To:References: Subject:Content-Type; b=CXaIAdATkW+xCnbdn6sfgOJg+EBk6pZuCGK0Zm3oaVPKcejZs5FnfP4ySvDQghtfeef7yOhwG+ei9VDX5eyS8PNfRRV8U0jH2dD45m5pw2LBeNZkEaKOvVV/+ZR4qUqbFbnWk8PYRLp+FHLjdlwlPPLW22DRJdj1N/7JhUVQG/k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de; spf=pass smtp.mailfrom=arndb.de; dkim=pass (2048-bit key) header.d=arndb.de header.i=@arndb.de header.b=C1hTxUvP; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b=iyQRqWqS; arc=none smtp.client-ip=202.12.124.138 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arndb.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=arndb.de header.i=@arndb.de header.b="C1hTxUvP"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="iyQRqWqS" Received: from phl-compute-07.internal (phl-compute-07.phl.internal [10.202.2.47]) by mailflow.stl.internal (Postfix) with ESMTP id 939871D41B86; Mon, 10 Mar 2025 17:21:06 -0400 (EDT) Received: from phl-imap-11 ([10.202.2.101]) by phl-compute-07.internal (MEProxy); Mon, 10 Mar 2025 17:21:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arndb.de; h=cc :cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to; s=fm3; t=1741641666; x=1741648866; bh=E4HKlxVjhIt2MzhfvIo5qMqiVK9k8HOzhVxjjAVbOk0=; b= C1hTxUvPA3Fb5iBKVyaB9S0GfSvuHye+iANMUYbqz2WEwKh+PjF2Ig9bEJQVXL8W kdPPlIgBhaXBR9cfmZ0PE2Am21WLFpDOSC8cX4CRdGVkwDQwLrkIeM5p0hpYbe13 dTxmdFfOvUlpJHQMFzsNCj740xYgX3HO88YG9+874W9W3ONJKWU3JnOvcNKUU/4u knNl6Vi+hohsFjz5X2QG4iDQUTaDl2o6gl+/SgTvwh+IxFXmzMQL8wdboNLh14A/ aarOTRDHRANpQ7jaacfHOdK2NKw4xhhoPCgcdkDHdrFJ9fRJG33i70Yr/2EzUjdG KxdDzQVgaqrYOM7VHlF73A== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm1; t=1741641666; x= 1741648866; bh=E4HKlxVjhIt2MzhfvIo5qMqiVK9k8HOzhVxjjAVbOk0=; b=i yQRqWqSGI6Kt3YUKxrmI/FlE9b26ffQwpxP94u4VFt4R8vOueVcX3AoCZMSsXlsf XL00t5hz0HKoZQiWWgBfXmCi3KczhguDU8kRNtshw4wzTjqLWf4R4c8bJijn8DFl 5yAnjsGkIz+NVAjzqe0v8OCUxD15L05INUOiZ6x/J4ac0ZBqVNbvzgRHbmj5t9Ba 3j6HgC/97L/dQ3YDHejXKY/xvQz/hLUQihBs2DCB1G8au5Q5PvHhOBLiHxE0gHPx sXxfmR9U/Us8LYPKZcy0PiBDAB8ri/wnT4GnQ5IYNOMthafCCbqTTLAJKEw4GxLS 2eWJA70Uin2M61IfU8uCQ== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdduvddtgeduucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdggtfgfnhhsuhgsshgtrhhisggv pdfurfetoffkrfgpnffqhgenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpih gvnhhtshculddquddttddmnecujfgurhepofggfffhvfevkfgjfhfutgfgsehtjeertder tddtnecuhfhrohhmpedftehrnhguuceuvghrghhmrghnnhdfuceorghrnhgusegrrhhnug gsrdguvgeqnecuggftrfgrthhtvghrnhephfdthfdvtdefhedukeetgefggffhjeeggeet fefggfevudegudevledvkefhvdeinecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrg hmpehmrghilhhfrhhomheprghrnhgusegrrhhnuggsrdguvgdpnhgspghrtghpthhtohep geefpdhmohguvgepshhmthhpohhuthdprhgtphhtthhopegsphesrghlihgvnhekrdguvg dprhgtphhtthhopegtrghtrghlihhnrdhmrghrihhnrghssegrrhhmrdgtohhmpdhrtghp thhtohepjhhovgihrdhgohhulhihsegrrhhmrdgtohhmpdhrtghpthhtohepmhgrrhhkrd hruhhtlhgrnhgusegrrhhmrdgtohhmpdhrtghpthhtohepshhuuggvvghprdhhohhllhgr segrrhhmrdgtohhmpdhrtghpthhtohepshhuiihukhhirdhpohhulhhoshgvsegrrhhmrd gtohhmpdhrtghpthhtohepsghhvghlghgrrghssehgohhoghhlvgdrtghomhdprhgtphht thhopeihuhiivghnghhhuhhisehhuhgrfigvihdrtghomhdprhgtphhtthhopegtohhnoh hrodgutheskhgvrhhnvghlrdhorhhg X-ME-Proxy: Feedback-ID: i56a14606:Fastmail Received: by mailuser.phl.internal (Postfix, from userid 501) id 2BEF92220072; Mon, 10 Mar 2025 17:21:05 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Mon, 10 Mar 2025 22:20:41 +0100 From: "Arnd Bergmann" To: "Michael Kelley" , "Roman Kisel" , "bhelgaas@google.com" , "Borislav Petkov" , "Catalin Marinas" , "Conor Dooley" , "Dave Hansen" , "Dexuan Cui" , "Haiyang Zhang" , "H. Peter Anvin" , "Joey Gouly" , "krzk+dt@kernel.org" , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , "K. Y. Srinivasan" , "Len Brown" , "Lorenzo Pieralisi" , "Manivannan Sadhasivam" , "Mark Rutland" , "Marc Zyngier" , "Ingo Molnar" , "Oliver Upton" , "Rafael J . Wysocki" , "Rob Herring" , "ssengar@linux.microsoft.com" , "Sudeep Holla" , "Suzuki K Poulose" , "Thomas Gleixner" , "Wei Liu" , "Will Deacon" , "Zenghui Yu" , "devicetree@vger.kernel.org" , "kvmarm@lists.linux.dev" , "linux-acpi@vger.kernel.org" , Linux-Arch , "linux-arm-kernel@lists.infradead.org" , "linux-hyperv@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "x86@kernel.org" Cc: "apais@microsoft.com" , "benhill@microsoft.com" , "bperkins@microsoft.com" , "sunilmut@microsoft.com" Message-Id: <119cfb59-d68b-4718-b7cb-90cba67827e8@app.fastmail.com> In-Reply-To: References: <20250307220304.247725-1-romank@linux.microsoft.com> <20250307220304.247725-4-romank@linux.microsoft.com> Subject: Re: [PATCH hyperv-next v5 03/11] Drivers: hv: Enable VTL mode for arm64 Content-Type: text/plain Content-Transfer-Encoding: 7bit On Mon, Mar 10, 2025, at 22:01, Michael Kelley wrote: > From: Arnd Bergmann Sent: Saturday, March 8, 2025 1:05 PM >> > config HYPERV_VTL_MODE >> > bool "Enable Linux to boot in VTL context" >> > - depends on X86_64 && HYPERV >> > + depends on (X86_64 || ARM64) >> > depends on SMP >> > + select OF_EARLY_FLATTREE >> > + select OF >> > default n >> > help >> >> Having the dependency below the top-level Kconfig entry feels a little >> counterintuitive. You could flip that back as it was before by doing >> >> select HYPERV_VTL_MODE if !ACPI >> depends on ACPI || SMP >> >> in the HYPERV option, leaving the dependency on HYPERV in >> HYPERV_VTL_MODE. > > I would argue that we don't ever want to implicitly select > HYPERV_VTL_MODE because of some other config setting or > lack thereof. VTL mode is enough of a special case that it should > only be explicitly selected. If someone omits ACPI, then HYPERV > should not be selectable unless HYPERV_VTL_MODE is explicitly > selected. > > The last line of the comment for HYPERV_VTL_MODE says > "A kernel built with this option must run at VTL2, and will not run > as a normal guest." In other words, don't choose this unless you > 100% know that VTL2 is what you want. It sounds like the latter is the real problem: enabling a feature should never prevent something else from working. Can you describe what VTL context is and why it requires an exception to a rather fundamental rule here? If you build a kernel that runs on every single piece of arm64 hardware and every hypervisor, why can't you add HYPERV_VTL_MODE to that as an option? Arnd