On Thu, Dec 14, 2023 at 07:08:32AM +0000, Chen, Jiqian wrote: > On 2023/12/13 20:12, Roger Pau Monné wrote: > > On Wed, Dec 13, 2023 at 03:31:21AM +0000, Chen, Jiqian wrote: > >> On 2023/12/12 17:18, Roger Pau Monné wrote: > >>> On Tue, Dec 12, 2023 at 06:34:27AM +0000, Chen, Jiqian wrote: > >>>> > >>>> On 2023/12/12 01:57, Roger Pau Monné wrote: > >>>>> On Mon, Dec 11, 2023 at 12:15:19AM +0800, Jiqian Chen wrote: > >>>>>> There is a need for some scenarios to use gsi sysfs. > >>>>>> For example, when xen passthrough a device to dumU, it will > >>>>>> use gsi to map pirq, but currently userspace can't get gsi > >>>>>> number. > >>>>>> So, add gsi sysfs for that and for other potential scenarios. > >>>>>> > >>>>>> Co-developed-by: Huang Rui <ray.huang@xxxxxxx> > >>>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx> > >>>>>> --- > >>>>>> drivers/acpi/pci_irq.c | 1 + > >>>>>> drivers/pci/pci-sysfs.c | 11 +++++++++++ > >>>>>> include/linux/pci.h | 2 ++ > >>>>>> 3 files changed, 14 insertions(+) > >>>>>> > >>>>>> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c > >>>>>> index 630fe0a34bc6..739a58755df2 100644 > >>>>>> --- a/drivers/acpi/pci_irq.c > >>>>>> +++ b/drivers/acpi/pci_irq.c > >>>>>> @@ -449,6 +449,7 @@ int acpi_pci_irq_enable(struct pci_dev *dev) > >>>>>> kfree(entry); > >>>>>> return 0; > >>>>>> } > >>>>>> + dev->gsi = gsi; > >>>>> > >>>>> It would be better if the gsi if fetched without requiring calling > >>>>> acpi_pci_irq_enable(), as the gsi doesn't require the interrupt to be > >>>>> enabled. The gsi is known at boot time and won't change for the > >>>>> lifetime of the device. > >>>> Do you have any suggest places to do this? > >>> > >>> I'm not an expert on this, but drivers/pci/pci-sysfs.c would seem like > >>> a better place, together with the rest of the resources. > >> I'm not familiar with this too. But it seems pci-sysfs.c only creates sysfs node and supports the read/write method without initializing the values. > >> If want to initialize the value of gsi here. An approach to initialize it is to call acpi_pci_irq_lookup to get gsi number when the first time it is read? > > > > Hm, maybe, I don't really have much experience with sysfs, so don't > > know how nodes are usually initialized. > Maybe the maintainers of sysfs can give some suggest places to initialize the value of gsi. > > > > >>> > >>> Maybe my understanding is incorrect, but given the suggested placement > >>> in acpi_pci_irq_enable() I think the device would need to bind the > >>> interrupt in order for the gsi node to appear on sysfs? > >> No, gsi sysfs has existed there, in acpi_pci_irq_enable is to initialize the value of gsi. > >> > >>> > >>> Would the current approach work if the device is assigned to pciback > >>> on the kernel command line, and thus never owned by any driver in > >>> dom0? > >> If assigned to pciback, I think pciback will enable the device, and then acpi_pci_irq_enable will be called, and then the gsi will be initialized. So, current can work. > > > > This needs checking to be sure, I'm certainly not that familiar. You > > would need to at least test that it works properly when the device is > > hidden using xen-pciback.hide=(SBDF) in the Linux kernel command line. > Sure, I have validated it on my side. Both the "Static assignment for built-in xen-pciback(xen-pciback.hide=(SBDF))" and the "Dynamic assignment with xl(sudo modprobe xen-pciback & sudo xl pci-assignable-add SBDF)" can work fine with current implementation. Oh, OK, if that's the case I don't have much objection in doing the initialization in acpi_pci_irq_enable(), that's an internal Linux detail. I mostly care about the GSI being exposed in sysfs in a non-Xen specific way. Thanks, Roger.
