linux-kernel - [PATCH v2 0/3] Drivers: hv: Avoid allocating MMIO from framebuffer region for other passed through PCI devices

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Date:   Thu, 25 Aug 2022 11:00:21 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linux-hyperv@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Wei Liu <wei.liu@...nel.org>,
        Deepak Rawat <drawat.floss@...il.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: [PATCH v2 0/3] Drivers: hv: Avoid allocating MMIO from framebuffer region for other passed through PCI devices

Changes since v1:
- Dropped PATCH2 as it is no longer needed.
- Move PCI ids to linux/pci_ids.h [Michael]
- Correctly handle "!(pdev->resource[0].flags & IORESOURCE_MEM)" case
  [Michael].

Passed through PCI device sometimes misbehave on Gen1 VMs when Hyper-V
DRM driver is also loaded. Looking at IOMEM assignment, we can see e.g.

$ cat /proc/iomem
...
f8000000-fffbffff : PCI Bus 0000:00
  f8000000-fbffffff : 0000:00:08.0
    f8000000-f8001fff : bb8c4f33-2ba2-4808-9f7f-02f3b4da22fe
...
fe0000000-fffffffff : PCI Bus 0000:00
  fe0000000-fe07fffff : bb8c4f33-2ba2-4808-9f7f-02f3b4da22fe
    fe0000000-fe07fffff : 2ba2:00:02.0
      fe0000000-fe07fffff : mlx4_core

the interesting part is the 'f8000000' region as it is actually the
VM's framebuffer:

$ lspci -v
...
0000:00:08.0 VGA compatible controller: Microsoft Corporation Hyper-V virtual VGA (prog-if 00 [VGA controller])
	Flags: bus master, fast devsel, latency 0, IRQ 11
	Memory at f8000000 (32-bit, non-prefetchable) [size=64M]
...

Recently merged commit a0ab5abced55 ("drm/hyperv : Removing the restruction of
VRAM allocation with PCI bar size") improved the situation as resources,
reserved through vmbus_allocate_mmio() can't be allocated twice:

...
f8000000-fffbffff : PCI Bus 0000:00
  f8000000-fbffffff : 0000:00:08.0
    f8000000-f8001fff : bb8c4f33-2ba2-4808-9f7f-02f3b4da22fe
    f8100000-f88fffff : 5620e0c7-8062-4dce-aeb7-520c7ef76171
...

Always reserve FB region on Gen1 VMs (PATCH2) and make sure we never allocate
anything besides framebuffer from there (PATCH3).

Vitaly Kuznetsov (3):
  PCI: Move PCI_VENDOR_ID_MICROSOFT/PCI_DEVICE_ID_HYPERV_VIDEO
    definitions to pci_ids.h
  Drivers: hv: Always reserve framebuffer region for Gen1 VMs
  Drivers: hv: Never allocate anything besides framebuffer from
    framebuffer memory region

 drivers/gpu/drm/hyperv/hyperv_drm_drv.c       |  3 -
 drivers/hv/vmbus_drv.c                        | 56 ++++++++++++++-----
 .../net/ethernet/microsoft/mana/gdma_main.c   |  4 --
 drivers/video/fbdev/hyperv_fb.c               |  4 --
 include/linux/pci_ids.h                       |  3 +
 5 files changed, 44 insertions(+), 26 deletions(-)

-- 
2.37.1