linux-kernel - [PATCH v2] drm/qxl: get vga ioports

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Message-Id: <20190805105401.29874-1-kraxel@redhat.com>
Date:   Mon,  5 Aug 2019 12:54:01 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Gerd Hoffmann <kraxel@...hat.com>,
        Frediano Ziglio <fziglio@...hat.com>,
        Dave Airlie <airlied@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        virtualization@...ts.linux-foundation.org (open list:DRM DRIVER FOR QXL
        VIRTUAL GPU),
        spice-devel@...ts.freedesktop.org (open list:DRM DRIVER FOR QXL VIRTUAL
        GPU), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] drm/qxl: get vga ioports

qxl has two modes: "native" (used by the drm driver) and "vga" (vga
compatibility mode, typically used for boot display and firmware
framebuffers).

Accessing any vga ioport will switch the qxl device into vga mode.
The qxl driver never does that, but other drivers accessing vga ports
can trigger that too and therefore disturb qxl operation.  So aquire
the legacy vga ioports from vgaarb to avoid that.

Reproducer: Boot kvm guest with both qxl and i915 vgpu, with qxl being
first in pci scan order.

v2: Skip this for secondary qxl cards which don't have vga mode in the
    first place (Frediano).

Cc: Frediano Ziglio <fziglio@...hat.com>
Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 drivers/gpu/drm/qxl/qxl_drv.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
index b57a37543613..fcb48ac60598 100644
--- a/drivers/gpu/drm/qxl/qxl_drv.c
+++ b/drivers/gpu/drm/qxl/qxl_drv.c
@@ -63,6 +63,11 @@ module_param_named(num_heads, qxl_num_crtc, int, 0400);
 static struct drm_driver qxl_driver;
 static struct pci_driver qxl_pci_driver;
 
+static bool is_vga(struct pci_dev *pdev)
+{
+	return pdev->class == PCI_CLASS_DISPLAY_VGA << 8;
+}
+
 static int
 qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
@@ -87,9 +92,17 @@ qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (ret)
 		goto disable_pci;
 
+	if (is_vga(pdev)) {
+		ret = vga_get_interruptible(pdev, VGA_RSRC_LEGACY_IO);
+		if (ret) {
+			DRM_ERROR("can't get legacy vga ioports\n");
+			goto disable_pci;
+		}
+	}
+
 	ret = qxl_device_init(qdev, &qxl_driver, pdev);
 	if (ret)
-		goto disable_pci;
+		goto put_vga;
 
 	ret = qxl_modeset_init(qdev);
 	if (ret)
@@ -109,6 +122,9 @@ qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	qxl_modeset_fini(qdev);
 unload:
 	qxl_device_fini(qdev);
+put_vga:
+	if (is_vga(pdev))
+		vga_put(pdev, VGA_RSRC_LEGACY_IO);
 disable_pci:
 	pci_disable_device(pdev);
 free_dev:
@@ -126,6 +142,8 @@ qxl_pci_remove(struct pci_dev *pdev)
 
 	qxl_modeset_fini(qdev);
 	qxl_device_fini(qdev);
+	if (is_vga(pdev))
+		vga_put(pdev, VGA_RSRC_LEGACY_IO);
 
 	dev->dev_private = NULL;
 	kfree(qdev);
-- 
2.18.1