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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v3 1/3] xen/igd: get PCH info from host sysfs
On 7/23/2026 9:09 AM, Tomita Moeko wrote:
> Sorry I am not the maintainer/reviewer of Xen IGD passthrough, just out
> of my personal interest
I appreciate your review. Thanks!
>
> On 2026-07-10 02:35, Chuck Zmudzinski wrote:
>> The igd_combo_id_infos[] data is more than 10 years
>> out of date with many Intel IGD devices missing from
>> igd_combo_id_infos[]. This means that many devices
>> that could be supported will not work with the
>> current implementation.
>>
>> For newer devices not listed in igd_combo_id_infos[],
>> get infos from the host sysfs to enable support for the
>> newer devices not listed in igd_combo_id_infos[].
>>
>> Introduce the helper function xen_pt_get_host_pch_info
>> to facilitate getting the necessary information from
>> sysfs.
>>
>> Also, use errp in xen_igd_passthrough_isa_bridge_create
>> to set errors from xen_pt_get_host_pch_info.
>>
>> Signed-off-by: Chuck Zmudzinski <brchuckz@xxxxxxx>
>> ---
>> Changes in v2:
>> - call error_setg* after closing files instead of before closing
>> files
>> - in last line of commit message change "to propagate errors" to
>> "to set errors"
>> - add stable to Cc list
>>
>> Changes in v3:
>> - whitespace fix at line 380 of xen_pt_graphics.c
>> - fix Cc address for qemu-stable
>>
>> hw/xen/xen_pt.c | 2 +-
>> hw/xen/xen_pt_graphics.c | 82 ++++++++++++++++++++++++++++++++++++++--
>> include/hw/xen/xen_igd.h | 3 +-
>> 3 files changed, 82 insertions(+), 5 deletions(-)
>>
>> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
>> index 0fe9c0a..474606e 100644
>> --- a/hw/xen/xen_pt.c
>> +++ b/hw/xen/xen_pt.c
>> @@ -867,7 +867,7 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
>> }
>>
>> /* Register ISA bridge for passthrough GFX. */
>> - xen_igd_passthrough_isa_bridge_create(s, &s->real_device);
>> + xen_igd_passthrough_isa_bridge_create(s, &s->real_device, errp);
>
> The `errp` need to be handled here if any error occurs.
>
>> }
>>
>> /* Handle real device's MMIO/PIO BARs */
>> diff --git a/hw/xen/xen_pt_graphics.c b/hw/xen/xen_pt_graphics.c
>> index 7df9344..2ef941e 100644
>> --- a/hw/xen/xen_pt_graphics.c
>> +++ b/hw/xen/xen_pt_graphics.c
>> @@ -376,8 +376,75 @@ static void pt_graphics_register_types(void)
>> }
>> type_init(pt_graphics_register_types)
>>
>> +static void xen_pt_get_host_pch_info(PCIDevice *dev, uint16_t *pch_dev_id,
>> + uint8_t *pch_rev_id, Error **errp)
>> +{
>> + FILE *fp1, *fp2;
>> + char *endptr;
>> + char device_id[7], rev[5];
>> + size_t len;
>> + const char *device = "/sys/bus/pci/devices/0000:00:1f.0/device";
>> + const char *revision = "/sys/bus/pci/devices/0000:00:1f.0/revision";
>> + unsigned long val;
>> +
>> + fp1 = fopen(device, "r");
>> + if (fp1 == NULL) {
>> + error_setg_errno(errp, errno, "Cannot open %s", device);
>> + return;
>> + }
>> + fp2 = fopen(revision, "r");
>> + if (fp2 == NULL) {
>> + fclose(fp1);
>> + error_setg_errno(errp, errno, "Cannot open %s", revision);
>> + return;
>> + }
>> +
>> + len = fread(device_id, 1, 7, fp1);
>> + if (!len) {
>> + fclose(fp1);
>> + fclose(fp2);
>> + error_setg(errp, "Cannot read %s", device);
>> + return;
>> + }
>> + len = fread(rev, 1, 5, fp2);
>> + if (!len) {
>> + fclose(fp1);
>> + fclose(fp2);
>> + error_setg(errp, "Cannot read %s", revision);
>> + return;
>> + }
>> + fclose(fp1);
>> + fclose(fp2);
>> +
>> + val = strtoul(device_id, &endptr, 16);
>> + if (val > 0xffff) {
>> + error_setg(errp, "PCH device id is out of range: 0x%lx", val);
>> + return;
>> + }
>> + if ((endptr > device_id) && (errno != ERANGE) &&
>> + (errno != EINVAL)) {
>> + *pch_dev_id = (uint16_t)val;
>> + } else {
>> + error_setg_errno(errp, errno, "device id strtoul "
>> + "conversion failed");
>> + return;
>> + }
>> + val = strtoul(rev, &endptr, 16);
>> + if (val > 0xff) {
>> + error_setg(errp, "PCH revision is out of range: 0x%lx", val);
>> + return;
>> + }
>> + if ((endptr > rev) && (errno != ERANGE) && (errno != EINVAL)) {
>> + *pch_rev_id = (uint8_t)val;
>> + } else {
>> + error_setg_errno(errp, errno, "revision strtoul "
>> + "conversion failed");
>> + }
>> +}
>> +
>
> It would be better to reuse existing xen_host_pci_device_get() to read host
> LPC bridge ids instead of parsing it on our own here.
Ah yes, I see how that can be done and I agree that would be better. I will
re-write xen_pt_get_host_pch_info() using the functions declared in
xen-host-pci-device.h for the next version of this patch.
>
>> void xen_igd_passthrough_isa_bridge_create(XenPCIPassthroughState *s,
>> - XenHostPCIDevice *dev)
>> + XenHostPCIDevice *dev,
>> + Error **errp)
>> {
>> PCIBus *bus = pci_get_bus(&s->dev);
>> struct PCIDevice *bridge_dev;
>> @@ -394,7 +461,16 @@ void
>> xen_igd_passthrough_isa_bridge_create(XenPCIPassthroughState *s,
>> }
>> }
>>
>> - if (pch_dev_id == 0xffff) {
>> + /* Newer devices get PCH infos from host sysfs */
>> + if ((pch_dev_id == 0xffff) || !pch_rev_id) {
>> + xen_pt_get_host_pch_info(&s->dev, &pch_dev_id, &pch_rev_id, errp);
>> + }
>> +
>> + XEN_PT_LOG(&s->dev, "PCH device id: 0x%x\n", pch_dev_id);
>> + XEN_PT_LOG(&s->dev, "PCH revision: 0x%x\n", pch_rev_id);
>> +
>> + if ((pch_dev_id == 0xffff) || !pch_rev_id) {
>> + error_setg(errp, "failed to get PCH device id or revision");
>> return;
>> }
>>
>> @@ -406,7 +482,7 @@ void
>> xen_igd_passthrough_isa_bridge_create(XenPCIPassthroughState *s,
>> * Note that vendor id is always PCI_VENDOR_ID_INTEL.
>> */
>> if (!bridge_dev) {
>> - fprintf(stderr, "set igd-passthrough-isa-bridge failed!\n");
>> + error_setg(errp, "set igd-passthrough-isa-bridge failed!");
>> return;
>> }
>> pci_config_set_device_id(bridge_dev->config, pch_dev_id);
>> diff --git a/include/hw/xen/xen_igd.h b/include/hw/xen/xen_igd.h
>> index 7ffca06..da51f09 100644
>> --- a/include/hw/xen/xen_igd.h
>> +++ b/include/hw/xen/xen_igd.h
>> @@ -22,7 +22,8 @@ uint32_t igd_read_opregion(XenPCIPassthroughState *s);
>> void xen_igd_reserve_slot(PCIBus *pci_bus);
>> void igd_write_opregion(XenPCIPassthroughState *s, uint32_t val);
>> void xen_igd_passthrough_isa_bridge_create(XenPCIPassthroughState *s,
>> - XenHostPCIDevice *dev);
>> + XenHostPCIDevice *dev,
>> + Error **errp);
>>
>> static inline bool is_igd_vga_passthrough(XenHostPCIDevice *dev)
>> {
>
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