[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: RFC: PCI devices passthrough on Arm design proposal

  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
  • Date: Fri, 17 Jul 2020 14:49:20 +0000
  • Accept-language: en-GB, en-US
  • Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=arm.com; dmarc=pass action=none header.from=arm.com; dkim=pass header.d=arm.com; arc=none
  • Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=16qJpWuyRsbkhE+DIkPMJSVXRYLtWIcIvHctzxkKtFk=; b=i0wp2mwMcC+n0wV0V4IMSuMgrr1CydpjCgecqmFgTlaUzQ9tsOlNBnQLcnZl2uVjdzYNK5PWZv0gxWnoXNOVqDrSDTTNdnAfXF1zskot1/Uum71ikuGTOKbIe2DhAJUQI9vShgAeT/Rv+SRZFeg1Y5N1QrxCYX/5X2OhUeOINdZt6nO8Vh4uqje/u4RFVMmMe2EiaViImJA9LrrO4Wks1yEa45h+4dFhrcNKyBOAdQ4fq16s/SnxzfsAY/M0VdAfQ2X3D/E2Mx5brOGHZHxywzxm1fzxzWvdID1J2qIYkjNtwit+Hpn3pxo845uGUyyMN2xpC8iA1sBj/uieKfjeqw==
  • Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=JFYGPPld2s0pHoquNnzfJR2e9ugJ3hMvGemck1/PtVuKSmapRF5r5PsG6wePg4FcNpIYNw2RkvSXFn/GholnfAnilCIaJXBvwnPCKCHHCZl4pj4PE84isFZo0PnrL3b1Kb1somgknmu7bKA9eXetiUzWFvwEs9sn6WBN3b7bpjISc/muAz9oJ18MqYmYSgpkXF5olGYHH2AQmePsybkydunsUO9FBEWp7PebjPEG95I4206P0+2IMyEvvd1bMf+nsYp0JYY7WPVYuPWc/bLuxzqwcaJKMxenEPAsf5tByDtxyQ3sGwg46KO3cJqUmLi5YEkmub8OQ4W1vVxTDs3EaQ==
  • Authentication-results-original: citrix.com; dkim=none (message not signed) header.d=none;citrix.com; dmarc=none action=none header.from=arm.com;
  • Cc: Rahul Singh <Rahul.Singh@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, nd <nd@xxxxxxx>, Julien Grall <julien.grall.oss@xxxxxxxxx>
  • Delivery-date: Fri, 17 Jul 2020 14:49:41 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Nodisclaimer: true
  • Original-authentication-results: citrix.com; dkim=none (message not signed) header.d=none;citrix.com; dmarc=none action=none header.from=arm.com;
  • Thread-topic: RFC: PCI devices passthrough on Arm design proposal

> On 17 Jul 2020, at 16:41, Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
> On Fri, Jul 17, 2020 at 02:34:55PM +0000, Bertrand Marquis wrote:
>>> On 17 Jul 2020, at 16:06, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>> On 17.07.2020 15:59, Bertrand Marquis wrote:
>>>>> On 17 Jul 2020, at 15:19, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>> On 17.07.2020 15:14, Bertrand Marquis wrote:
>>>>>>> On 17 Jul 2020, at 10:10, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>>>> On 16.07.2020 19:10, Rahul Singh wrote:
>>>>>>>> # Emulated PCI device tree node in libxl:
>>>>>>>> Libxl is creating a virtual PCI device tree node in the device tree to 
>>>>>>>> enable the guest OS to discover the virtual PCI during guest boot. We 
>>>>>>>> introduced the new config option [vpci="pci_ecam"] for guests. When 
>>>>>>>> this config option is enabled in a guest configuration, a PCI device 
>>>>>>>> tree node will be created in the guest device tree.
>>>>>>> I support Stefano's suggestion for this to be an optional thing, i.e.
>>>>>>> there to be no need for it when there are PCI devices assigned to the
>>>>>>> guest anyway. I also wonder about the pci_ prefix here - isn't
>>>>>>> vpci="ecam" as unambiguous?
>>>>>> This could be a problem as we need to know that this is required for a 
>>>>>> guest upfront so that PCI devices can be assigned after using xl. 
>>>>> I'm afraid I don't understand: When there are no PCI device that get
>>>>> handed to a guest when it gets created, but it is supposed to be able
>>>>> to have some assigned while already running, then we agree the option
>>>>> is needed (afaict). When PCI devices get handed to the guest while it
>>>>> gets constructed, where's the problem to infer this option from the
>>>>> presence of PCI devices in the guest configuration?
>>>> If the user wants to use xl pci-attach to attach in runtime a device to a 
>>>> guest, this guest must have a VPCI bus (even with no devices).
>>>> If we do not have the vpci parameter in the configuration this use case 
>>>> will not work anymore.
>>> That's what everyone looks to agree with. Yet why is the parameter needed
>>> when there _are_ PCI devices anyway? That's the "optional" that Stefano
>>> was suggesting, aiui.
>> I agree in this case the parameter could be optional and only required if 
>> not PCI device is assigned directly in the guest configuration.
> Where will the ECAM region(s) appear on the guest physmap?
> Are you going to re-use the same locations as on the physical
> hardware, or will they appear somewhere else?

We will add some new definitions for the ECAM regions in the guest physmap 
declared in xen (include/asm-arm/config.h)
So they will appear at a different address then the hardware.


> Roger.



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.