vfio-pci: Add support for VGA region access

PCI defines display class VGA regions at I/O port address 0x3b0, 0x3c0
and MMIO address 0xa0000.  As these are non-overlapping, we can ignore
the I/O port vs MMIO difference and expose them both in a single
region.  We make use of the VGA arbiter around each access to
configure chipset access as necessary.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

5 files changed, 102 insertions, 0 deletions

diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 5980758563eb..e84300b268b6 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -6,3 +6,13 @@ config VFIO_PCI
           use of PCI drivers using the VFIO framework.
 
           If you don't know what to do here, say N.
+
+config VFIO_PCI_VGA
+        bool "VFIO PCI support for VGA devices"
+        depends on VFIO_PCI && X86 && VGA_ARB && EXPERIMENTAL
+        help
+          Support for VGA extension to VFIO PCI.  This exposes an additional
+          region on VGA devices for accessing legacy VGA addresses used by
+          BIOS and generic video drivers.
+
+          If you don't know what to do here, say N.
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index bb8c8c2be960..8189cb6a86af 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -84,6 +84,11 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
         } else
                 vdev->msix_bar = 0xFF;
 
+#ifdef CONFIG_VFIO_PCI_VGA
+        if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
+                vdev->has_vga = true;
+#endif
+
         return 0;
 }
 
@@ -285,6 +290,16 @@ static long vfio_pci_ioctl(void *device_data,
                         info.flags = VFIO_REGION_INFO_FLAG_READ;
                         break;
                 }
+                case VFIO_PCI_VGA_REGION_INDEX:
+                        if (!vdev->has_vga)
+                                return -EINVAL;
+
+                        info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
+                        info.size = 0xc0000;
+                        info.flags = VFIO_REGION_INFO_FLAG_READ |
+                                     VFIO_REGION_INFO_FLAG_WRITE;
+
+                        break;
                 default:
                         return -EINVAL;
                 }
@@ -386,6 +401,9 @@ static ssize_t vfio_pci_rw(void *device_data, char __user *buf,
 
         case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
                 return vfio_pci_bar_rw(vdev, buf, count, ppos, iswrite);
+
+        case VFIO_PCI_VGA_REGION_INDEX:
+                return vfio_pci_vga_rw(vdev, buf, count, ppos, iswrite);
         }
 
         return -EINVAL;
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 00d19b953ce4..d7e55d03f49e 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -53,6 +53,7 @@ struct vfio_pci_device {
         bool                    reset_works;
         bool                    extended_caps;
         bool                    bardirty;
+        bool                    has_vga;
         struct pci_saved_state  *pci_saved_state;
         atomic_t                refcnt;
 };
@@ -77,6 +78,9 @@ extern ssize_t vfio_pci_config_rw(struct vfio_pci_device *vdev,
 extern ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
                                size_t count, loff_t *ppos, bool iswrite);
 
+extern ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
+                               size_t count, loff_t *ppos, bool iswrite);
+
 extern int vfio_pci_init_perm_bits(void);
 extern void vfio_pci_uninit_perm_bits(void);
 
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index e9d78eb91ed7..210db24d2204 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -17,6 +17,7 @@
 #include <linux/pci.h>
 #include <linux/uaccess.h>
 #include <linux/io.h>
+#include <linux/vgaarb.h>
 
 #include "vfio_pci_private.h"
 
@@ -175,3 +176,63 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
 
         return done;
 }
+
+ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
+                               size_t count, loff_t *ppos, bool iswrite)
+{
+        int ret;
+        loff_t off, pos = *ppos & VFIO_PCI_OFFSET_MASK;
+        void __iomem *iomem = NULL;
+        unsigned int rsrc;
+        bool is_ioport;
+        ssize_t done;
+
+        if (!vdev->has_vga)
+                return -EINVAL;
+
+        switch (pos) {
+        case 0xa0000 ... 0xbffff:
+                count = min(count, (size_t)(0xc0000 - pos));
+                iomem = ioremap_nocache(0xa0000, 0xbffff - 0xa0000 + 1);
+                off = pos - 0xa0000;
+                rsrc = VGA_RSRC_LEGACY_MEM;
+                is_ioport = false;
+                break;
+        case 0x3b0 ... 0x3bb:
+                count = min(count, (size_t)(0x3bc - pos));
+                iomem = ioport_map(0x3b0, 0x3bb - 0x3b0 + 1);
+                off = pos - 0x3b0;
+                rsrc = VGA_RSRC_LEGACY_IO;
+                is_ioport = true;
+                break;
+        case 0x3c0 ... 0x3df:
+                count = min(count, (size_t)(0x3e0 - pos));
+                iomem = ioport_map(0x3c0, 0x3df - 0x3c0 + 1);
+                off = pos - 0x3c0;
+                rsrc = VGA_RSRC_LEGACY_IO;
+                is_ioport = true;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        if (!iomem)
+                return -ENOMEM;
+
+        ret = vga_get_interruptible(vdev->pdev, rsrc);
+        if (ret) {
+                is_ioport ? ioport_unmap(iomem) : iounmap(iomem);
+                return ret;
+        }
+
+        done = do_io_rw(iomem, buf, off, count, 0, 0, iswrite);
+
+        vga_put(vdev->pdev, rsrc);
+
+        is_ioport ? ioport_unmap(iomem) : iounmap(iomem);
+
+        if (done >= 0)
+                *ppos += done;
+
+        return done;
+}
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 4758d1bfcf41..4f41f309911e 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -303,6 +303,15 @@ enum {
         VFIO_PCI_BAR5_REGION_INDEX,
         VFIO_PCI_ROM_REGION_INDEX,
         VFIO_PCI_CONFIG_REGION_INDEX,
+        /*
+         * Expose VGA regions defined for PCI base class 03, subclass 00.
+         * This includes I/O port ranges 0x3b0 to 0x3bb and 0x3c0 to 0x3df
+         * as well as the MMIO range 0xa0000 to 0xbffff.  Each implemented
+         * range is found at it's identity mapped offset from the region
+         * offset, for example 0x3b0 is region_info.offset + 0x3b0.  Areas
+         * between described ranges are unimplemented.
+         */
+        VFIO_PCI_VGA_REGION_INDEX,
         VFIO_PCI_NUM_REGIONS
 };