Re: [KERNEL PATCH v9 3/3] xen/privcmd: Add new syscall to get gsi from dev

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 20 Sep 2024, Chen, Jiqian wrote:
> On 2024/9/19 06:49, Stefano Stabellini wrote:
> > On Thu, 12 Sep 2024, Jiqian Chen wrote:
> >> On PVH dom0, when passthrough a device to domU, QEMU and xl tools
> >> want to use gsi number to do pirq mapping, see QEMU code
> >> xen_pt_realize->xc_physdev_map_pirq, and xl code
> >> pci_add_dm_done->xc_physdev_map_pirq, but in current codes, the gsi
> >> number is got from file /sys/bus/pci/devices/<sbdf>/irq, that is
> >> wrong, because irq is not equal with gsi, they are in different
> >> spaces, so pirq mapping fails.
> >> And in current linux codes, there is no method to get gsi
> >> for userspace.
> >>
> >> For above purpose, record gsi of pcistub devices when init
> >> pcistub and add a new syscall into privcmd to let userspace
> >> can get gsi when they have a need.
> >>
> >> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> >> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> >> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> >> ---
> >> v8->v9 changes:
> >> Changed the syscall name from "IOCTL_PRIVCMD_GSI_FROM_DEV" to 
> >> "IOCTL_PRIVCMD_PCIDEV_GET_GSI". Also changed the other functions name.
> >> Changed the macro wrapping "pcistub_get_gsi_from_sbdf" from 
> >> "CONFIG_XEN_ACPI" to "CONFIG_XEN_PCIDEV_BACKEND" to fix compile errors 
> >> reported by CI robot.
> >> Changed the parameter gsi of struct privcmd_pcidev_get_gsi from int to u32.
> >>
> >> v7->v8 changes:
> >> In function privcmd_ioctl_gsi_from_dev, return -EINVAL when not confige 
> >> CONFIG_XEN_ACPI.
> >> Used PCI_BUS_NUM PCI_SLOT PCI_FUNC instead of open coding.
> >>
> >> v6->v7 changes:
> >> Changed implementation to add a new parameter "gsi" to struct 
> >> pcistub_device and set gsi when pcistub initialize device. Then when 
> >> userspace wants to get gsi and pass sbdf, we can return that gsi.
> >>
> >> v5->v6 changes:
> >> Changed implementation to add a new syscall to translate irq to gsi, 
> >> instead adding a new gsi sysfs node, because the pci Maintainer didn't 
> >> allow to add that sysfs node.
> >>
> >> v3->v5 changes:
> >> No.
> >>
> >> v2->v3 changes:
> >> Suggested by Roger: Abandoned previous implementations that added new 
> >> syscall to get gsi from irq and changed to add a new sysfs node for gsi, 
> >> then userspace can get gsi number from sysfs node.
> >> ---
> >> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> >> | Closes: 
> >> https://lore.kernel.org/oe-kbuild-all/202406090826.whl6Cb7R-lkp@xxxxxxxxx/
> >> ---
> >> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> >> | Closes: 
> >> https://lore.kernel.org/oe-kbuild-all/202405171113.T431PC8O-lkp@xxxxxxxxx/
> >> ---
> >>  drivers/xen/privcmd.c              | 30 +++++++++++++++++++++++
> >>  drivers/xen/xen-pciback/pci_stub.c | 38 +++++++++++++++++++++++++++---
> >>  include/uapi/xen/privcmd.h         |  7 ++++++
> >>  include/xen/acpi.h                 |  9 +++++++
> >>  4 files changed, 81 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> >> index 9563650dfbaf..1ed612d21543 100644
> >> --- a/drivers/xen/privcmd.c
> >> +++ b/drivers/xen/privcmd.c
> >> @@ -46,6 +46,9 @@
> >>  #include <xen/page.h>
> >>  #include <xen/xen-ops.h>
> >>  #include <xen/balloon.h>
> >> +#ifdef CONFIG_XEN_ACPI
> >> +#include <xen/acpi.h>
> >> +#endif
> >>  
> >>  #include "privcmd.h"
> >>  
> >> @@ -844,6 +847,29 @@ static long privcmd_ioctl_mmap_resource(struct file 
> >> *file,
> >>    return rc;
> >>  }
> >>  
> >> +static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user 
> >> *udata)
> >> +{
> >> +#ifdef CONFIG_XEN_ACPI
> >> +  int rc;
> >> +  struct privcmd_pcidev_get_gsi kdata;
> >> +
> >> +  if (copy_from_user(&kdata, udata, sizeof(kdata)))
> >> +          return -EFAULT;
> >> +
> >> +  rc = pcistub_get_gsi_from_sbdf(kdata.sbdf);
> >> +  if (rc < 0)
> >> +          return rc;
> >> +
> >> +  kdata.gsi = rc;
> >> +  if (copy_to_user(udata, &kdata, sizeof(kdata)))
> >> +          return -EFAULT;
> >> +
> >> +  return 0;
> >> +#else
> >> +  return -EINVAL;
> >> +#endif
> >> +}
> >> +
> >>  #ifdef CONFIG_XEN_PRIVCMD_EVENTFD
> >>  /* Irqfd support */
> >>  static struct workqueue_struct *irqfd_cleanup_wq;
> >> @@ -1543,6 +1569,10 @@ static long privcmd_ioctl(struct file *file,
> >>            ret = privcmd_ioctl_ioeventfd(file, udata);
> >>            break;
> >>  
> >> +  case IOCTL_PRIVCMD_PCIDEV_GET_GSI:
> >> +          ret = privcmd_ioctl_pcidev_get_gsi(file, udata);
> >> +          break;
> >> +
> >>    default:
> >>            break;
> >>    }
> >> diff --git a/drivers/xen/xen-pciback/pci_stub.c 
> >> b/drivers/xen/xen-pciback/pci_stub.c
> >> index 8ce27333f54b..2ea8e4075adc 100644
> >> --- a/drivers/xen/xen-pciback/pci_stub.c
> >> +++ b/drivers/xen/xen-pciback/pci_stub.c
> >> @@ -56,6 +56,9 @@ struct pcistub_device {
> >>  
> >>    struct pci_dev *dev;
> >>    struct xen_pcibk_device *pdev;/* non-NULL if struct pci_dev is in use */
> >> +#ifdef CONFIG_XEN_ACPI
> >> +  int gsi;
> >> +#endif
> >>  };
> >>  
> >>  /* Access to pcistub_devices & seized_devices lists and the 
> >> initialize_devices
> >> @@ -88,6 +91,9 @@ static struct pcistub_device 
> >> *pcistub_device_alloc(struct pci_dev *dev)
> >>  
> >>    kref_init(&psdev->kref);
> >>    spin_lock_init(&psdev->lock);
> >> +#ifdef CONFIG_XEN_ACPI
> >> +  psdev->gsi = -1;
> >> +#endif
> >>  
> >>    return psdev;
> >>  }
> >> @@ -220,6 +226,25 @@ static struct pci_dev 
> >> *pcistub_device_get_pci_dev(struct xen_pcibk_device *pdev,
> >>    return pci_dev;
> >>  }
> >>  
> >> +#ifdef CONFIG_XEN_PCIDEV_BACKEND
> > 
> > 
> > This breaks configurations without CONFIG_ACPI and with
> > CONFIG_XEN_PCIDEV_BACKEND.
> > 
> > Also there should be no dependency between PCIDEV_BACKEND and
> > pcistub_get_gsi_from_sbdf.
> > 
> > I think we should solve the build issues this way:
> > 
> > - privcmd_ioctl_pcidev_get_gsi should have:
> > #if defined(CONFIG_XEN_ACPI) && defined(CONFIG_XEN_PCI_STUB)
> > 
> > - here we should have #ifdef CONFIG_XEN_ACPI as you had before
> > 
> > 
> > As far as I can tell the above should be able to address all valid
> > combinations.
> This can't pass a combination that:
> CONFIG_XEN_ACPI=y
> CONFIG_XEN_PCI_STUB=y
> CONFIG_XEN_PCIDEV_BACKEND=m
> Reported by robot 
> https://lore.kernel.org/oe-kbuild-all/202406090826.whl6Cb7R-lkp@xxxxxxxxx/
> 
> At this combination, privcmd_ioctl_pcidev_get_gsi can call 
> pcistub_get_gsi_from_sbdf because CONFIG_XEN_ACPI and CONFIG_XEN_PCI_STUB are 
> both "y".
> But when the compiler tries to find the implementation of 
> pcistub_get_gsi_from_sbdf, it fails (ld: vmlinux.o: in function 
> `privcmd_ioctl_pcidev_get_gsi':
> /home/cjq/code/upstream/kernel_test_robot/linux_xen/build_dir/../drivers/xen/privcmd.c:859:
>  undefined reference to `pcistub_get_gsi_from_sbdf'), because the value of 
> CONFIG_XEN_PCIDEV_BACKEND is "m" (file drivers/xen/xen-pciback/Makefile shows 
> "obj-$(CONFIG_XEN_PCIDEV_BACKEND) += xen-pciback.o"), so that xen-pciback is 
> built as a module.


The attached .config, with the appended changes on top of your patch
work for me. I have CONFIG_XEN_PCIDEV_BACKEND=m.


diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 1ed612d21543..49e1c5e0c32a 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -849,7 +849,7 @@ static long privcmd_ioctl_mmap_resource(struct file *file,
 
 static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user *udata)
 {
-#ifdef CONFIG_XEN_ACPI
+#if defined(CONFIG_XEN_ACPI) && defined(CONFIG_XEN_PCI_STUB)
        int rc;
        struct privcmd_pcidev_get_gsi kdata;
 
diff --git a/drivers/xen/xen-pciback/pci_stub.c 
b/drivers/xen/xen-pciback/pci_stub.c
index 2ea8e4075adc..d5807b622a59 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -226,7 +226,7 @@ static struct pci_dev *pcistub_device_get_pci_dev(struct 
xen_pcibk_device *pdev,
        return pci_dev;
 }
 
-#ifdef CONFIG_XEN_PCIDEV_BACKEND
+#ifdef CONFIG_ACPI
 int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
 {
        struct pcistub_device *psdev;

Attachment: .config
Description: Text document