linux-kernel - Re: [PATCH v12 1/1] vfio/nvgpu: Add vfio pci variant module for grace hopper

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Message-ID: <BY5PR12MB376365035E31B569D767D636B0AFA@BY5PR12MB3763.namprd12.prod.outlook.com>
Date:   Thu, 9 Nov 2023 04:27:00 +0000
From:   Ankit Agrawal <ankita@...dia.com>
To:     Alex Williamson <alex.williamson@...hat.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Yishai Hadas <yishaih@...dia.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        Aniket Agashe <aniketa@...dia.com>, Neo Jia <cjia@...dia.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        "Tarun Gupta (SW-GPU)" <targupta@...dia.com>,
        Vikram Sethi <vsethi@...dia.com>,
        Andy Currid <acurrid@...dia.com>,
        Alistair Popple <apopple@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Dan Williams <danw@...dia.com>,
        "Anuj Aggarwal (SW-GPU)" <anuaggarwal@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 1/1] vfio/nvgpu: Add vfio pci variant module for grace
 hopper

> In light of that, I don't think we should be independently calculating
> the BAR2 region size using roundup_pow_of_two(nvdev->memlength).
> Instead we should be using pci_resource_len() of the physical BAR2 to
> make it evident that this relationship exists.

Just wanted to update on the discussions.. Since the underlying physical
BAR is not being used at all, we will emulate the PCI config BAR registers
for the fake BAR. Thus, the read/write requests to those registers will not
go to the underlying BAR on the device. I'll make the change in the next
posting.