From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-of-o52.zoho.com (sender4-of-o52.zoho.com [136.143.188.52]) (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 E19D530F7FA; Wed, 28 Jan 2026 16:16:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.52 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769617014; cv=pass; b=iu6LM+4bQ6TDmep0ehq2inWf1e7q+/vgsByebkCAYqDSkCo5hLjGQujtBIfcEv4Teh0MpMGAZTqCjep+0hbjBWJ4i1h/5eAHCi6fe7NLr0coJ3fMR7RXVPzLc+2iH8YEG/3U1sQ1b7OD4z8RWuoHS0T/nfMPHLTMyNqBGF8IocA= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769617014; c=relaxed/simple; bh=/wuVYwi7s0O8zwXGCPAHdXllatt/4FyTREtTRjgZc5Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EoW5zjoW7DTAgGiqooAbH1A/6XdWg/EKIXZDpdWrAvGHFQxUePLQND6yLCZptznrclcI/m/wiXi6yIGgGNiyQBQq50loPRiw5OVgSxvk0aSgYQFRc5922Mdd+3ecUiXXgh1ZaK93tOwikCDo8bg6uHP8zfT4xObfHWxthpvxkD8= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=anirudhrb.com; spf=pass smtp.mailfrom=anirudhrb.com; dkim=pass (1024-bit key) header.d=anirudhrb.com header.i=anirudh@anirudhrb.com header.b=B1odQAXh; arc=pass smtp.client-ip=136.143.188.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=anirudhrb.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=anirudhrb.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=anirudhrb.com header.i=anirudh@anirudhrb.com header.b="B1odQAXh" ARC-Seal: i=1; a=rsa-sha256; t=1769617002; cv=none; d=zohomail.com; s=zohoarc; b=EWdIQ+Y+fNOiL4opFblwpM1oVDthLOcbxc6/GFiC8QyAdN+LWc3a+XZqCRcLbpc7K9G1ZMNI8AMX+T5BpUAb5ZXjuMbtnQEs5OOj2tty09edf/5Qg6eUweaHMPSBfgx1Q3yWom10ZVSEP+Fm8ErdfLbq8wKDlVMn9bGbNkiQOV8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1769617002; h=Content-Type:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=0QawbTxuXnc3bO/oeGvHR8vV16XTXUszsuyQFERjUVc=; b=WO7BUbLj8axEsVCbwA/6Q9MaCPND677Lo5QwDxGHaVsZEuJ0+b0EC5+6Nb5PMEDNykOXbmuK/fUr+ZS18SliinMi/JAfrUvl2BKRNFXrO6qfoXvBDmP/NXgbr3BLuJd7K7GYorTOYYGtua2lz51K6Y6gLoHGseBGLUsQs6QOWDM= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=anirudhrb.com; spf=pass smtp.mailfrom=anirudh@anirudhrb.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1769617002; s=zoho; d=anirudhrb.com; i=anirudh@anirudhrb.com; h=Date:Date:From:From:To:To:Cc:Cc:Subject:Subject:Message-ID:References:MIME-Version:Content-Type:In-Reply-To:Message-Id:Reply-To; bh=0QawbTxuXnc3bO/oeGvHR8vV16XTXUszsuyQFERjUVc=; b=B1odQAXheh/z5v4Hu/lumQv3RjlfB+4/cY68gnCWv0zRPaomf3IWPvYjVHUwGMqJ q81WSZ/qHEF7qX0bAXKDdBaWgsui2+CvcKsLdj0B8YHSBwfJ8SpQ/9otRxXUYNNExbT 2rJtbclAaJiYiVIZzn3ubLlE9mr72rer69hthzuc= Received: by mx.zohomail.com with SMTPS id 17696169983261006.4672516716466; Wed, 28 Jan 2026 08:16:38 -0800 (PST) Date: Wed, 28 Jan 2026 16:16:31 +0000 From: Anirudh Rayabharam To: Stanislav Kinsburskii Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mshv: Make MSHV mutually exclusive with KEXEC Message-ID: References: <176920684805.250171.6817228088359793537.stgit@skinsburskii-cloud-desktop.internal.cloudapp.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: X-ZohoMailClient: External On Mon, Jan 26, 2026 at 12:46:44PM -0800, Stanislav Kinsburskii wrote: > On Tue, Jan 27, 2026 at 12:19:24AM +0530, Anirudh Rayabharam wrote: > > On Fri, Jan 23, 2026 at 10:20:53PM +0000, Stanislav Kinsburskii wrote: > > > The MSHV driver deposits kernel-allocated pages to the hypervisor during > > > runtime and never withdraws them. This creates a fundamental incompatibility > > > with KEXEC, as these deposited pages remain unavailable to the new kernel > > > loaded via KEXEC, leading to potential system crashes upon kernel accessing > > > hypervisor deposited pages. > > > > > > Make MSHV mutually exclusive with KEXEC until proper page lifecycle > > > management is implemented. > > > > Someone might want to stop all guest VMs and do a kexec. Which is valid > > and would work without any issue for L1VH. > > > > No, it won't work and hypervsisor depostied pages won't be withdrawn. All pages that were deposited in the context of a guest partition (i.e. with the guest partition ID), would be withdrawn when you kill the VMs, right? What other deposited pages would be left? Thanks, Anirudh. > Also, kernel consisntency must no depend on use space behavior. > > > Also, I don't think it is reasonable at all that someone needs to > > disable basic kernel functionality such as kexec in order to use our > > driver. > > > > It's a temporary measure until proper page lifecycle management is > supported in the driver. > Mutual exclusion of the driver and kexec is given and thus should be > expclitily stated in the Kconfig. > > Thanks, > Stanislav > > > Thanks, > > Anirudh. > > > > > > > > Signed-off-by: Stanislav Kinsburskii > > > --- > > > drivers/hv/Kconfig | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig > > > index 7937ac0cbd0f..cfd4501db0fa 100644 > > > --- a/drivers/hv/Kconfig > > > +++ b/drivers/hv/Kconfig > > > @@ -74,6 +74,7 @@ config MSHV_ROOT > > > # e.g. When withdrawing memory, the hypervisor gives back 4k pages in > > > # no particular order, making it impossible to reassemble larger pages > > > depends on PAGE_SIZE_4KB > > > + depends on !KEXEC > > > select EVENTFD > > > select VIRT_XFER_TO_GUEST_WORK > > > select HMM_MIRROR > > > > > >