Re: [PATCH 2/2] xen: fix stubdom PCI addr

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Mon, Feb 19, 2024 at 07:16:06PM +0100, Marek Marczykowski-Górecki wrote:
> From: Frédéric Pierret (fepitre) <frederic.pierret@qubes-os.org>

This shouldn't be here, it's my patch.

> When running in a stubdomain, the config space access via sysfs needs to
> use BDF as seen inside stubdomain (connected via xen-pcifront), which is
> different from the real BDF. For other purposes (hypercall parameters
> etc), the real BDF needs to be used.
> Get the in-stubdomain BDF by looking up relevant PV PCI xenstore
> entries.
> 
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> ---
>  hw/xen/xen-host-pci-device.c | 77 +++++++++++++++++++++++++++++++++++-
>  hw/xen/xen-host-pci-device.h |  6 +++
>  2 files changed, 82 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
> index 8c6e9a1716..3f8a6f84a8 100644
> --- a/hw/xen/xen-host-pci-device.c
> +++ b/hw/xen/xen-host-pci-device.c
> @@ -9,6 +9,7 @@
>  #include "qemu/osdep.h"
>  #include "qapi/error.h"
>  #include "qemu/cutils.h"
> +#include "hw/xen/xen-legacy-backend.h"
>  #include "xen-host-pci-device.h"
>  
>  #define XEN_HOST_PCI_MAX_EXT_CAP \
> @@ -33,13 +34,76 @@
>  #define IORESOURCE_PREFETCH     0x00001000      /* No side effects */
>  #define IORESOURCE_MEM_64       0x00100000
>  
> +static void xen_host_pci_fill_local_addr(XenHostPCIDevice *d, Error **errp)
> +{
> +    unsigned int num_devs, len, i;
> +    unsigned int domain, bus, dev, func;
> +    char *be_path = NULL;
> +    char path[80];
> +    char *msg = NULL;
> +
> +    be_path = qemu_xen_xs_read(xenstore, 0, "device/pci/0/backend", &len);
> +    if (!be_path)
> +        goto err_out;
> +    snprintf(path, sizeof(path), "%s/num_devs", be_path);
> +    msg = qemu_xen_xs_read(xenstore, 0, path, &len);
> +    if (!msg)
> +        goto err_out;
> +
> +    if (sscanf(msg, "%u", &num_devs) != 1) {
> +        error_setg(errp, "Failed to parse %s (%s)\n", msg, path);
> +        goto err_out;
> +    }
> +    free(msg);
> +
> +    for (i = 0; i < num_devs; i++) {
> +        snprintf(path, sizeof(path), "%s/dev-%u", be_path, i);
> +        msg = qemu_xen_xs_read(xenstore, 0, path, &len);
> +        if (!msg) {
> +            error_setg(errp, "Failed to read %s\n", path);
> +            goto err_out;
> +        }
> +        if (sscanf(msg, "%x:%x:%x.%x", &domain, &bus, &dev, &func) != 4) {
> +            error_setg(errp, "Failed to parse %s (%s)\n", msg, path);
> +            goto err_out;
> +        }
> +        free(msg);
> +        if (domain != d->domain ||
> +                bus != d->bus ||
> +                dev != d->dev ||
> +                func!= d->func)
> +            continue;
> +        snprintf(path, sizeof(path), "%s/vdev-%u", be_path, i);
> +        msg = qemu_xen_xs_read(xenstore, 0, path, &len);
> +        if (!msg) {
> +            error_setg(errp, "Failed to read %s\n", path);
> +            goto out;
> +        }
> +        if (sscanf(msg, "%x:%x:%x.%x", &domain, &bus, &dev, &func) != 4) {
> +            error_setg(errp, "Failed to parse %s (%s)\n", msg, path);
> +            goto err_out;
> +        }
> +        free(msg);
> +        d->local_domain = domain;
> +        d->local_bus = bus;
> +        d->local_dev = dev;
> +        d->local_func = func;
> +        goto out;
> +    }
> +
> +err_out:
> +    free(msg);
> +out:
> +    free(be_path);
> +}
> +
>  static void xen_host_pci_sysfs_path(const XenHostPCIDevice *d,
>                                      const char *name, char *buf, ssize_t size)
>  {
>      int rc;
>  
>      rc = snprintf(buf, size, "/sys/bus/pci/devices/%04x:%02x:%02x.%d/%s",
> -                  d->domain, d->bus, d->dev, d->func, name);
> +                  d->local_domain, d->local_bus, d->local_dev, d->local_func, name);
>      assert(rc >= 0 && rc < size);
>  }
>  
> @@ -342,6 +406,17 @@ void xen_host_pci_device_get(XenHostPCIDevice *d, uint16_t domain,
>      d->dev = dev;
>      d->func = func;
>  
> +    if (xen_is_stubdomain) {
> +        xen_host_pci_fill_local_addr(d, errp);
> +        if (*errp)
> +            goto error;
> +    } else {
> +        d->local_domain = d->domain;
> +        d->local_bus = d->bus;
> +        d->local_dev = d->dev;
> +        d->local_func = d->func;
> +    }
> +
>      xen_host_pci_config_open(d, errp);
>      if (*errp) {
>          goto error;
> diff --git a/hw/xen/xen-host-pci-device.h b/hw/xen/xen-host-pci-device.h
> index 4d8d34ecb0..270dcb27f7 100644
> --- a/hw/xen/xen-host-pci-device.h
> +++ b/hw/xen/xen-host-pci-device.h
> @@ -23,6 +23,12 @@ typedef struct XenHostPCIDevice {
>      uint8_t dev;
>      uint8_t func;
>  
> +    /* different from the above in case of stubdomain */
> +    uint16_t local_domain;
> +    uint8_t local_bus;
> +    uint8_t local_dev;
> +    uint8_t local_func;
> +
>      uint16_t vendor_id;
>      uint16_t device_id;
>      uint32_t class_code;
> -- 
> 2.43.0
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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