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Re: [RFC QEMU PATCH v3 1/1] xen: Use gsi instead of irq for mapping pirq
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: "Chen, Jiqian" <Jiqian.Chen@xxxxxxx>
- Date: Tue, 12 Dec 2023 06:37:00 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony Perard <anthony.perard@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, "qemu-devel@xxxxxxxxxx" <qemu-devel@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "Ragiadakou, Xenia" <Xenia.Ragiadakou@xxxxxxx>, "Hildebrand, Stewart" <Stewart.Hildebrand@xxxxxxx>, "Deucher, Alexander" <Alexander.Deucher@xxxxxxx>, "Huang, Ray" <Ray.Huang@xxxxxxx>, "Huang, Honglei1" <Honglei1.Huang@xxxxxxx>, "Zhang, Julia" <Julia.Zhang@xxxxxxx>, "Chen, Jiqian" <Jiqian.Chen@xxxxxxx>
- Delivery-date: Tue, 12 Dec 2023 06:37:09 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHaK4lXtH9e9Sdr6Eux87H1RxVtTrCkN9cAgAGB1YA=
- Thread-topic: [RFC QEMU PATCH v3 1/1] xen: Use gsi instead of irq for mapping pirq
On 2023/12/11 23:33, Roger Pau Monné wrote:
> On Mon, Dec 11, 2023 at 12:52:40AM +0800, Jiqian Chen wrote:
>> In PVH dom0, it uses the linux local interrupt mechanism,
>> when it allocs irq for a gsi, it is dynamic, and follow
>> the principle of applying first, distributing first. And
>> the irq number is alloced from small to large, but the
>> applying gsi number is not, may gsi 38 comes before gsi
>> 28, that causes the irq number is not equal with the gsi
>> number. And when passthrough a device, qemu wants to use
>> gsi to map pirq, xen_pt_realize->xc_physdev_map_pirq, but
>> the gsi number is got from file
>> /sys/bus/pci/devices/<sbdf>/irq in current code, so it
>> will fail when mapping.
>>
>> Use real gsi number read from gsi sysfs.
>>
>> Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
>> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
>> ---
>> hw/xen/xen-host-pci-device.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
>> index 8c6e9a1716..e270ac2631 100644
>> --- a/hw/xen/xen-host-pci-device.c
>> +++ b/hw/xen/xen-host-pci-device.c
>> @@ -364,7 +364,7 @@ void xen_host_pci_device_get(XenHostPCIDevice *d,
>> uint16_t domain,
>> }
>> d->device_id = v;
>>
>> - xen_host_pci_get_dec_value(d, "irq", &v, errp);
>> + xen_host_pci_get_dec_value(d, "gsi", &v, errp);
>
> Don't you need to fallthrough to use the irq number on failure?
> Otherwise passthrough won't work on older Linux versions that don't
> expose the gsi node.
You are right, I will use the irq if there isn't a gsi sysfs, in next version.
Thank you.
>
> Thanks, Roger.
--
Best regards,
Jiqian Chen.
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