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From: Jan Beulich <jbeulich@suse.com>
To: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>,
	Oleksandr Andrushchenko <andr2000@gmail.com>
Cc: "julien@xen.org" <julien@xen.org>,
	"sstabellini@kernel.org" <sstabellini@kernel.org>,
	Oleksandr Tyshchenko <Oleksandr_Tyshchenko@epam.com>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	Artem Mygaiev <Artem_Mygaiev@epam.com>,
	"roger.pau@citrix.com" <roger.pau@citrix.com>,
	Bertrand Marquis <bertrand.marquis@arm.com>,
	Rahul Singh <rahul.singh@arm.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 8/9] vpci/header: Reset the command register when adding devices
Date: Thu, 9 Sep 2021 13:53:56 +0200	[thread overview]
Message-ID: <06560d04-6d71-bb94-20af-fc43cf686b0a@suse.com> (raw)
In-Reply-To: <3ca10b3a-35c9-00b4-f736-293589d641d4@epam.com>

On 09.09.2021 13:48, Oleksandr Andrushchenko wrote:
> On 09.09.21 12:21, Jan Beulich wrote:
>> For the bit in question, where the goal appears to be to have hardware
>> hold the OR of guest and host values, an approach similar to that used
>> for some of the MSI / MSI-X bits might be chosen: Maintain guest and
>> host bits in software, and update hardware (at least) when the
>> effective resulting value changes. A complicating fact here is, though,
>> that unlike for the MSI / MSI-X bits here Dom0 (pciback or its PCI
>> susbstem) may also have a view on what the setting ought to be.
> 
> The bigger question here is what can we take as the reference for INTx
> bit, e.g. if Dom0 didn't enable/configured the device being passed through
> than its COMMAND register may still be in after reset state and IMO there is
> no guarantee it has the values we can say are "as host wants them"

In the absence of Dom0 controlling the device, I think we ought to take
Xen's view as the "host" one. Which will want the bit set at least as
long as either MSI or MSI-X is enabled for the device.

Jan



  reply	other threads:[~2021-09-09 11:54 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-03 10:08 [PATCH 0/9] PCI devices passthrough on Arm, part 3 Oleksandr Andrushchenko
2021-09-03 10:08 ` [PATCH 1/9] vpci: Make vpci registers removal a dedicated function Oleksandr Andrushchenko
2021-09-03 10:08 ` [PATCH 2/9] vpci: Add hooks for PCI device assign/de-assign Oleksandr Andrushchenko
2021-09-06 13:23   ` Jan Beulich
2021-09-07  8:33     ` Oleksandr Andrushchenko
2021-09-07  8:44       ` Jan Beulich
2021-09-03 10:08 ` [PATCH 3/9] vpci/header: Move register assignments from init_bars Oleksandr Andrushchenko
2021-09-06 13:53   ` Jan Beulich
2021-09-07 10:04     ` Oleksandr Andrushchenko
2021-09-03 10:08 ` [PATCH 4/9] vpci/header: Add and remove register handlers dynamically Oleksandr Andrushchenko
2021-09-06 14:11   ` Jan Beulich
2021-09-07 10:11     ` Oleksandr Andrushchenko
2021-09-07 10:43       ` Jan Beulich
2021-09-07 11:10         ` Oleksandr Andrushchenko
2021-09-07 11:49           ` Jan Beulich
2021-09-07 12:16             ` Oleksandr Andrushchenko
2021-09-07 12:20               ` Jan Beulich
2021-09-07 12:23                 ` Oleksandr Andrushchenko
2021-09-10 21:14   ` Stefano Stabellini
2021-09-03 10:08 ` [PATCH 5/9] vpci/header: Implement guest BAR register handlers Oleksandr Andrushchenko
2021-09-06 14:31   ` Jan Beulich
2021-09-07 13:33     ` Oleksandr Andrushchenko
2021-09-07 16:30       ` Jan Beulich
2021-09-07 17:39         ` Oleksandr Andrushchenko
2021-09-08  9:27           ` Jan Beulich
2021-09-08  9:43             ` Oleksandr Andrushchenko
2021-09-08 10:03               ` Jan Beulich
2021-09-08 13:33                 ` Oleksandr Andrushchenko
2021-09-08 14:46                   ` Jan Beulich
2021-09-08 15:14                     ` Oleksandr Andrushchenko
2021-09-08 15:29                       ` Jan Beulich
2021-09-08 15:35                         ` Oleksandr Andrushchenko
2021-09-03 10:08 ` [PATCH 6/9] vpci/header: Handle p2m range sets per BAR Oleksandr Andrushchenko
2021-09-06 14:47   ` Jan Beulich
2021-09-08 14:31     ` Oleksandr Andrushchenko
2021-09-08 15:00       ` Jan Beulich
2021-09-09  5:22         ` Oleksandr Andrushchenko
2021-09-09  8:24           ` Jan Beulich
2021-09-09  9:12             ` Oleksandr Andrushchenko
2021-09-09  9:39               ` Jan Beulich
2021-09-09 10:03                 ` Oleksandr Andrushchenko
2021-09-09 10:46                   ` Jan Beulich
2021-09-09 11:30                     ` Oleksandr Andrushchenko
2021-09-09 11:51                       ` Jan Beulich
2021-09-03 10:08 ` [PATCH 7/9] vpci/header: program p2m with guest BAR view Oleksandr Andrushchenko
2021-09-06 14:51   ` Jan Beulich
2021-09-09  6:13     ` Oleksandr Andrushchenko
2021-09-09  8:26       ` Jan Beulich
2021-09-09  9:16         ` Oleksandr Andrushchenko
2021-09-09  9:40           ` Jan Beulich
2021-09-09  9:53             ` Oleksandr Andrushchenko
2021-09-03 10:08 ` [PATCH 8/9] vpci/header: Reset the command register when adding devices Oleksandr Andrushchenko
2021-09-06 14:55   ` Jan Beulich
2021-09-07  7:43     ` Oleksandr Andrushchenko
2021-09-07  8:00       ` Jan Beulich
2021-09-07  8:18         ` Oleksandr Andrushchenko
2021-09-07  8:49           ` Jan Beulich
2021-09-07  9:07             ` Oleksandr Andrushchenko
2021-09-07  9:19               ` Jan Beulich
2021-09-07  9:52                 ` Oleksandr Andrushchenko
2021-09-07 10:06                   ` Jan Beulich
2021-09-09  8:39                     ` Oleksandr Andrushchenko
2021-09-09  8:43                       ` Jan Beulich
2021-09-09  8:50                         ` Oleksandr Andrushchenko
2021-09-09  9:21                           ` Jan Beulich
2021-09-09 11:48                             ` Oleksandr Andrushchenko
2021-09-09 11:53                               ` Jan Beulich [this message]
2021-09-09 12:42                                 ` Oleksandr Andrushchenko
2021-09-09 12:47                                   ` Jan Beulich
2021-09-09 12:48                                     ` Oleksandr Andrushchenko
2021-09-09 13:17                                     ` Oleksandr Andrushchenko
2021-09-09 11:48                             ` Oleksandr Andrushchenko
2021-09-03 10:08 ` [PATCH 9/9] vpci/header: Use pdev's domain instead of vCPU Oleksandr Andrushchenko
2021-09-06 14:57   ` Jan Beulich
2021-09-09  4:23     ` Oleksandr Andrushchenko

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