From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7E5813DABE3; Fri, 21 Aug 2026 10:14:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787307311; cv=none; b=LFpGHG/QAPhgir/0Edjf2ZuwXUkkpXS+rl0qy3EvsJIFmhOZ8PM/PRgUSOhpTKqiK+rVq4+ol4JqdrfwABcmCHrZfysV0R77rkw0cfwVHsmWtt/DsiGChePHcagKNuE+7Mz/mUDvTXOLZC2PF1mfYGS1uHtyuiAjvFzXR+t1vb8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787307311; c=relaxed/simple; bh=x2PW7k3TwIFcVb0HgB/a2qRx2lQJd10nFtvVhrzqC8Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KuXxUTqlQx8JV3irVgq6oeX0xWojOoqYVg7QzmuTz05n2a8nVJFxOOP5TvX+eSU4SQM0xVAkGqRcQolWRhIgIm3uhmAKrX6yFORXSCfmMyad/8mofdGk5LZUXVNUfNjfHejJr7ZKbPXdQtC4vCiSQFWcFstIuFmqV8SGO2/ovBI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=FuYRMiGd; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="FuYRMiGd" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4920A153B; Fri, 21 Aug 2026 03:14:50 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 14E803F66F; Fri, 21 Aug 2026 03:14:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1787307294; bh=x2PW7k3TwIFcVb0HgB/a2qRx2lQJd10nFtvVhrzqC8Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FuYRMiGderCL7nMqslzfHOA6euy0UBOD1xqRTMH9+k081cdWWc08S4DdYXjkt+Sal boFmmz6ePE8ZDTU+icV/5pr531uWUWcQXyMj2Wc5+zy1PRn5+91yD8wOHdNoP4RuA4 x8vzVwd5pN4HQ78h03aRbZpZZ0ZLjboqoXvsE7kc= Date: Fri, 21 Aug 2026 11:14:49 +0100 From: Catalin Marinas To: Shradha Gupta Cc: Will Deacon , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, Mark Rutland , Marc Zyngier , Michael Kelley , Shradha Gupta Subject: Re: [RFC PATCH 0/2] arm64/hyperv: Enable kexec reboot support Message-ID: References: <20260814093133.3191250-1-shradhagupta@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-hyperv@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: <20260814093133.3191250-1-shradhagupta@linux.microsoft.com> On Fri, Aug 14, 2026 at 02:31:28AM -0700, Shradha Gupta wrote: > Kexec reboot consistently fails on ARM64 Hyper-V guests (Azure VMs). > During the kexec shutdown path, VMBus channels are never cleaned up, > so in the fresh kexec kernel startup hv_acpi_init() blocks because > the hypervisor still holds the old kernel's VMBus session open. > > This is because ARM64 lacks the VMBus teardown that x86 performs during > kexec via hv_machine_shutdown(). On x86, machine_ops.shutdown is > overridden to send CHANNELMSG_UNLOAD and disable SynIC before CPUs > go offline. ARM64 has no equivalent mechanism. I'm really not keen on such hook, a bare pointer you set elsewhere. Not sure it was discussed before but can you not use the syscore_shutdown() mechanism? This hook got added in 2023, so the 2022 discussion you referenced precedes it. -- Catalin