Re: [Qemu-devel] [v5][PATCH 1/5] xen, gfx passthrough: basic graphics passthrough support

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 25, 2014 at 10:17:17AM +0800, Tiejun Chen wrote:
> basic gfx passthrough support:
> - add a vga type for gfx passthrough
> - retrieve VGA bios from sysfs, then load it to guest at 0xC0000
> - register/unregister legacy VGA I/O ports and MMIOs for passthrough GFX
> 
> The original patch is from Weidong Han <weidong.han@intel.com>
> 
> Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
> Cc: Weidong Han <weidong.han@intel.com>

ROM loading code is duplicated from assigned_dev_load_option_rom.
Would it be a problem for you to create a memory region holding
the ROM?
You won't need cpu_physical_memory_rw then, either, or need
the VGA_BIOS_DEFAULT_SIZE hack.




> ---
> v5:
> 
> * Just rebase.
> 
> v4:
> 
> * Fix some typos in the patch head description.
> * Improve some comments.
> * Given that xen_pt_register_vga_regions()/xen_pt_unregister_vga_regions()
>   are called unconditionally, so we just return 0 there.
> * Remove one spurious change.
> 
> v3:
> 
> * Fix some typos.
> * Add more comments to make that readable.
> * Improve some return paths.
> 
> v2:
> 
> * retrieve VGA bios from sysfs properly.
> * redefine some function name.
> 
>  hw/xen/Makefile.objs         |   2 +-
>  hw/xen/xen-host-pci-device.c |   5 +
>  hw/xen/xen-host-pci-device.h |   1 +
>  hw/xen/xen_pt.c              |  10 ++
>  hw/xen/xen_pt.h              |   4 +
>  hw/xen/xen_pt_graphics.c     | 232 +++++++++++++++++++++++++++++++++++++++++++
>  qemu-options.hx              |   9 ++
>  vl.c                         |  10 ++
>  8 files changed, 272 insertions(+), 1 deletion(-)
>  create mode 100644 hw/xen/xen_pt_graphics.c
> 
> diff --git a/hw/xen/Makefile.objs b/hw/xen/Makefile.objs
> index a0ca0aa..77b7dae 100644
> --- a/hw/xen/Makefile.objs
> +++ b/hw/xen/Makefile.objs
> @@ -2,4 +2,4 @@
>  common-obj-$(CONFIG_XEN_BACKEND) += xen_backend.o xen_devconfig.o
>  
>  obj-$(CONFIG_XEN_PCI_PASSTHROUGH) += xen-host-pci-device.o
> -obj-$(CONFIG_XEN_PCI_PASSTHROUGH) += xen_pt.o xen_pt_config_init.o xen_pt_msi.o
> +obj-$(CONFIG_XEN_PCI_PASSTHROUGH) += xen_pt.o xen_pt_config_init.o xen_pt_msi.o xen_pt_graphics.o
> diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
> index 743b37b..a54b7de 100644
> --- a/hw/xen/xen-host-pci-device.c
> +++ b/hw/xen/xen-host-pci-device.c
> @@ -376,6 +376,11 @@ int xen_host_pci_device_get(XenHostPCIDevice *d, uint16_t domain,
>          goto error;
>      }
>      d->irq = v;
> +    rc = xen_host_pci_get_hex_value(d, "class", &v);
> +    if (rc) {
> +        goto error;
> +    }
> +    d->class_code = v;
>      d->is_virtfn = xen_host_pci_dev_is_virtfn(d);
>  
>      return 0;
> diff --git a/hw/xen/xen-host-pci-device.h b/hw/xen/xen-host-pci-device.h
> index c2486f0..f1e1c30 100644
> --- a/hw/xen/xen-host-pci-device.h
> +++ b/hw/xen/xen-host-pci-device.h
> @@ -25,6 +25,7 @@ typedef struct XenHostPCIDevice {
>  
>      uint16_t vendor_id;
>      uint16_t device_id;
> +    uint32_t class_code;
>      int irq;
>  
>      XenHostPCIIORegion io_regions[PCI_NUM_REGIONS - 1];
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index be4220b..dac4238 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -450,6 +450,7 @@ static int xen_pt_register_regions(XenPCIPassthroughState *s)
>                     d->rom.size, d->rom.base_addr);
>      }
>  
> +    xen_pt_register_vga_regions(d);
>      return 0;
>  }
>  
> @@ -470,6 +471,8 @@ static void xen_pt_unregister_regions(XenPCIPassthroughState *s)
>      if (d->rom.base_addr && d->rom.size) {
>          memory_region_destroy(&s->rom);
>      }
> +
> +    xen_pt_unregister_vga_regions(d);
>  }
>  
>  /* region mapping */
> @@ -693,6 +696,13 @@ static int xen_pt_initfn(PCIDevice *d)
>      /* Handle real device's MMIO/PIO BARs */
>      xen_pt_register_regions(s);
>  
> +    /* Setup VGA bios for passthrough GFX */
> +    if (xen_pt_setup_vga(&s->real_device) < 0) {
> +        XEN_PT_ERR(d, "Setup VGA BIOS of passthrough GFX failed!\n");
> +        xen_host_pci_device_put(&s->real_device);
> +        return -1;
> +    }
> +
>      /* reinitialize each config register to be emulated */
>      if (xen_pt_config_init(s)) {
>          XEN_PT_ERR(d, "PCI Config space initialisation failed.\n");
> diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
> index 942dc60..4d3a18d 100644
> --- a/hw/xen/xen_pt.h
> +++ b/hw/xen/xen_pt.h
> @@ -298,5 +298,9 @@ static inline bool xen_pt_has_msix_mapping(XenPCIPassthroughState *s, int bar)
>      return s->msix && s->msix->bar_index == bar;
>  }
>  
> +extern int xen_has_gfx_passthru;
> +int xen_pt_register_vga_regions(XenHostPCIDevice *dev);
> +int xen_pt_unregister_vga_regions(XenHostPCIDevice *dev);
> +int xen_pt_setup_vga(XenHostPCIDevice *dev);
>  
>  #endif /* !XEN_PT_H */
> diff --git a/hw/xen/xen_pt_graphics.c b/hw/xen/xen_pt_graphics.c
> new file mode 100644
> index 0000000..461e526
> --- /dev/null
> +++ b/hw/xen/xen_pt_graphics.c
> @@ -0,0 +1,232 @@
> +/*
> + * graphics passthrough
> + */
> +#include "xen_pt.h"
> +#include "xen-host-pci-device.h"
> +#include "hw/xen/xen_backend.h"
> +
> +static int is_vga_passthrough(XenHostPCIDevice *dev)
> +{
> +    return (xen_has_gfx_passthru
> +            && ((dev->class_code >> 0x8) == PCI_CLASS_DISPLAY_VGA));
> +}
> +
> +typedef struct VGARegion {
> +    int type;           /* Memory or port I/O */
> +    uint64_t guest_base_addr;
> +    uint64_t machine_base_addr;
> +    uint64_t size;    /* size of the region */
> +    int rc;
> +} VGARegion;
> +
> +#define IORESOURCE_IO           0x00000100
> +#define IORESOURCE_MEM          0x00000200
> +
> +static struct VGARegion vga_args[] = {
> +    {
> +        .type = IORESOURCE_IO,
> +        .guest_base_addr = 0x3B0,
> +        .machine_base_addr = 0x3B0,
> +        .size = 0xC,
> +        .rc = -1,
> +    },
> +    {
> +        .type = IORESOURCE_IO,
> +        .guest_base_addr = 0x3C0,
> +        .machine_base_addr = 0x3C0,
> +        .size = 0x20,
> +        .rc = -1,
> +    },
> +    {
> +        .type = IORESOURCE_MEM,
> +        .guest_base_addr = 0xa0000 >> XC_PAGE_SHIFT,
> +        .machine_base_addr = 0xa0000 >> XC_PAGE_SHIFT,
> +        .size = 0x20,
> +        .rc = -1,
> +    },
> +};
> +
> +/*
> + * register VGA resources for the domain with assigned gfx
> + */
> +int xen_pt_register_vga_regions(XenHostPCIDevice *dev)
> +{
> +    int i = 0;
> +
> +    if (!is_vga_passthrough(dev)) {
> +        return 0;
> +    }
> +
> +    for (i = 0 ; i < ARRAY_SIZE(vga_args); i++) {
> +        if (vga_args[i].type == IORESOURCE_IO) {
> +            vga_args[i].rc = xc_domain_ioport_mapping(xen_xc, xen_domid,
> +                            vga_args[i].guest_base_addr,
> +                            vga_args[i].machine_base_addr,
> +                            vga_args[i].size, DPCI_ADD_MAPPING);
> +        } else {
> +            vga_args[i].rc = xc_domain_memory_mapping(xen_xc, xen_domid,
> +                            vga_args[i].guest_base_addr,
> +                            vga_args[i].machine_base_addr,
> +                            vga_args[i].size, DPCI_ADD_MAPPING);
> +        }
> +
> +        if (vga_args[i].rc) {
> +            XEN_PT_ERR(NULL, "VGA %s mapping failed! (rc: %i)\n",
> +                    vga_args[i].type == IORESOURCE_IO ? "ioport" : "memory",
> +                    vga_args[i].rc);
> +            return vga_args[i].rc;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +/*
> + * unregister VGA resources for the domain with assigned gfx
> + */
> +int xen_pt_unregister_vga_regions(XenHostPCIDevice *dev)
> +{
> +    int i = 0;
> +
> +    if (!is_vga_passthrough(dev)) {
> +        return 0;
> +    }
> +
> +    for (i = 0 ; i < ARRAY_SIZE(vga_args); i++) {
> +        if (vga_args[i].type == IORESOURCE_IO) {
> +            vga_args[i].rc = xc_domain_ioport_mapping(xen_xc, xen_domid,
> +                            vga_args[i].guest_base_addr,
> +                            vga_args[i].machine_base_addr,
> +                            vga_args[i].size, DPCI_REMOVE_MAPPING);
> +        } else {
> +            vga_args[i].rc = xc_domain_memory_mapping(xen_xc, xen_domid,
> +                            vga_args[i].guest_base_addr,
> +                            vga_args[i].machine_base_addr,
> +                            vga_args[i].size, DPCI_REMOVE_MAPPING);
> +        }
> +
> +        if (vga_args[i].rc) {
> +            XEN_PT_ERR(NULL, "VGA %s unmapping failed! (rc: %i)\n",
> +                    vga_args[i].type == IORESOURCE_IO ? "ioport" : "memory",
> +                    vga_args[i].rc);
> +            return vga_args[i].rc;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static int get_vgabios(unsigned char *buf, XenHostPCIDevice *dev)
> +{
> +    char rom_file[64];
> +    FILE *fp;
> +    uint8_t val;
> +    struct stat st;
> +    uint16_t magic = 0;
> +    int ret = 0;
> +
> +    snprintf(rom_file, sizeof(rom_file),
> +             "/sys/bus/pci/devices/%04x:%02x:%02x.%d/rom",
> +             dev->domain, dev->bus, dev->dev,
> +             dev->func);
> +
> +    if (stat(rom_file, &st)) {
> +        return -ENODEV;
> +    }
> +
> +    if (access(rom_file, F_OK)) {
> +        XEN_PT_ERR(NULL, "pci-assign: Insufficient privileges for %s",
> +                    rom_file);
> +        return -ENODEV;
> +    }
> +
> +    /* Write "1" to the ROM file to enable it */
> +    fp = fopen(rom_file, "r+");
> +    if (fp == NULL) {
> +        return -EACCES;
> +    }
> +    val = 1;
> +    if (fwrite(&val, 1, 1, fp) != 1) {
> +        XEN_PT_LOG("%s\n", "Failed to enable pci-sysfs rom file");
> +        ret = -EIO;
> +        goto close_rom;
> +    }
> +    fseek(fp, 0, SEEK_SET);
> +
> +    /*
> +     * Check if it a real bios extension.
> +     * The magic number is 0xAA55.
> +     */
> +    if (!fread(&magic, sizeof(magic), 1, fp)) {
> +        XEN_PT_ERR(NULL, "VGA: can't get magic.\n");
> +        ret = -ENODEV;
> +        goto close_rom;
> +    }
> +    if (magic != 0xAA55) {
> +        XEN_PT_ERR(NULL, "VGA: wrong magic %x.\n", magic);
> +        ret = -ENODEV;
> +        goto close_rom;
> +    }
> +    fseek(fp, 0, SEEK_SET);
> +
> +    if (!fread(buf, 1, st.st_size, fp)) {
> +        XEN_PT_ERR(NULL, "VGA: pci-assign: Cannot read from host %s", rom_file);
> +        XEN_PT_LOG(NULL, "VGA: Device option ROM contents are probably invalid "
> +                     "(check dmesg).\nSkip option ROM probe with rombar=0, "
> +                     "or load from file with romfile=\n");
> +    }
> +
> +close_rom:
> +    /* Write "0" to disable ROM */
> +    fseek(fp, 0, SEEK_SET);
> +    val = 0;
> +    if (!fwrite(&val, 1, 1, fp)) {
> +        ret = -EIO;
> +        XEN_PT_LOG("%s\n", "Failed to disable pci-sysfs rom file");
> +    }
> +    fclose(fp);
> +    return ret;
> +}
> +
> +/* Allocated 128K for the vga bios */
> +#define VGA_BIOS_DEFAULT_SIZE (0x20000)
> +
> +int xen_pt_setup_vga(XenHostPCIDevice *dev)
> +{
> +    unsigned char *bios = NULL;
> +    int bios_size = 0;
> +    char *c = NULL;
> +    char checksum = 0;
> +    int rc = 0;
> +
> +    if (!is_vga_passthrough(dev)) {
> +        return rc;
> +    }
> +
> +    bios = g_malloc0(VGA_BIOS_DEFAULT_SIZE);
> +
> +    bios_size = get_vgabios(bios, dev);
> +    if (bios_size) {
> +        XEN_PT_ERR(NULL, "VGA: Error %d getting VBIOS!\n", bios_size);
> +        if (bios_size < 0) {
> +            XEN_PT_ERR(NULL, "VGA: Error (%s).\n", strerror(bios_size));
> +        }
> +        rc = -1;
> +        goto out;
> +    }
> +
> +    /* Adjust the bios checksum */

It's easy to see that you do this here, but *why* do you do it?
That's what the comment should explain.
Do you see many ROMs with an invalid checksum
in the field?

> +    for (c = (char *)bios; c < ((char *)bios + bios_size); c++) {
> +        checksum += *c;
> +    }
> +    if (checksum) {
> +        bios[bios_size - 1] -= checksum;
> +        XEN_PT_LOG(NULL, "vga bios checksum is adjusted!\n");
> +    }
> +
> +    /* Currently we fixed this address as a primary. */
> +    cpu_physical_memory_rw(0xc0000, bios, bios_size, 1);
> +out:
> +    g_free(bios);
> +    return rc;
> +}
> diff --git a/qemu-options.hx b/qemu-options.hx
> index ff76ad4..1c77baa 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1066,6 +1066,15 @@ STEXI
>  Rotate graphical output some deg left (only PXA LCD).
>  ETEXI
>  
> +DEF("gfx_passthru", 0, QEMU_OPTION_gfx_passthru,
> +    "-gfx_passthru   enable Intel IGD passthrough by XEN\n",
> +    QEMU_ARCH_ALL)
> +STEXI
> +@item -gfx_passthru
> +@findex -gfx_passthru
> +Enable Intel IGD passthrough by XEN
> +ETEXI
> +
>  DEF("vga", HAS_ARG, QEMU_OPTION_vga,
>      "-vga [std|cirrus|vmware|qxl|xenfb|tcx|cg3|none]\n"
>      "                select video card type\n", QEMU_ARCH_ALL)
> diff --git a/vl.c b/vl.c
> index a1686ef..c5b572d 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1418,6 +1418,13 @@ static void configure_msg(QemuOpts *opts)
>      enable_timestamp_msg = qemu_opt_get_bool(opts, "timestamp", true);
>  }
>  
> +/* We still need this for compatibility with XEN. */
> +int xen_has_gfx_passthru;
> +static void xen_gfx_passthru(const char *optarg)
> +{
> +    xen_has_gfx_passthru = 1;
> +}
> +
>  /***********************************************************/
>  /* USB devices */
>  
> @@ -3945,6 +3952,9 @@ int main(int argc, char **argv, char **envp)
>                      exit(1);
>                  }
>                  break;
> +            case QEMU_OPTION_gfx_passthru:
> +                xen_gfx_passthru(optarg);
> +                break;
>              default:
>                  os_parse_cmd_args(popt->index, optarg);
>              }
> -- 
> 1.9.1