Re: [Qemu-devel] [PATCH] xen-hvm: stop faking I/O to access PCI config space

[Anthony PERARD <anthony.perard@citrix.com>]

On Thu, May 03, 2018 at 12:18:40PM +0100, Paul Durrant wrote:
> This patch removes the current hackery where IOREQ_TYPE_PCI_CONFIG
> reqyests are handled by faking PIO to 0xcf8 and 0xcfc and replaces it

  ^ requests

> with direct calls to pci_host_config_read/write_common().
> Doing so necessitates mapping BDFs to PCIDevices but maintaining a simple
> QLIST in xen_device_realize/unrealize() will suffice.
> 
> NOTE: whilst config space accesses are currently limited to
>       PCI_CONFIG_SPACE_SIZE, this patch paves the way to increasing the
>       limit to PCIE_CONFIG_SPACE_SIZE when Xen gains the ability to
>       emulate MCFG table accesses.
> 
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

> +static void cpu_ioreq_config(XenIOState *state, ioreq_t *req)
> +{
> +    uint32_t sbdf = req->addr >> 32;
> +    uint32_t reg = req->addr;
> +    XenPciDevice *xendev;
> +
> +    if (req->size > sizeof(uint32_t)) {
> +        hw_error("PCI config access: bad size (%u)", req->size);
> +    }
> +
> +    QLIST_FOREACH(xendev, &state->dev_list, entry) {
> +        unsigned int i;
> +
> +        if (xendev->sbdf != sbdf) {
> +            continue;
> +        }
> +
> +        if (req->dir == IOREQ_READ) {
> +            if (!req->data_is_ptr) {
> +                req->data = pci_host_config_read_common(
> +                    xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE,
> +                    req->size);
> +                trace_cpu_ioreq_config_read(req, sbdf, reg, req->size,
> +                                            req->data);
> +            } else {
> +                for (i = 0; i < req->count; i++) {
> +                    uint32_t tmp;
> +
> +                    tmp = pci_host_config_read_common(
> +                        xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE,
> +                        req->size);

So, if data is a pointer, we just keep reading the same address
req->count time?

> +                    write_phys_req_item(req->data, req, i, &tmp);
> +                }
> +            }
> +        } else if (req->dir == IOREQ_WRITE) {
> +            if (!req->data_is_ptr) {
> +                trace_cpu_ioreq_config_write(req, sbdf, reg, req->size,
> +                                             req->data);
> +                pci_host_config_write_common(
> +                    xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE, req->data,
> +                    req->size);
> +            } else {
> +                for (i = 0; i < req->count; i++) {
> +                    uint32_t tmp = 0;
> +
> +                    read_phys_req_item(req->data, req, i, &tmp);
> +                    pci_host_config_write_common(
> +                        xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE, tmp,
> +                        req->size);
> +                }
> +            }
> +        }
> +    }
> +}

-- 
Anthony PERARD