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Message-ID: <a7d2a3e8-e2f1-4175-b74c-2e27a909c25d@suse.com>
Date: Mon, 23 Sep 2024 10:04:07 +0200
From: Juergen Gross <jgross@...e.com>
To: "Chen, Jiqian" <Jiqian.Chen@....com>,
Stefano Stabellini <sstabellini@...nel.org>
Cc: "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Huang, Ray" <Ray.Huang@....com>
Subject: Re: [KERNEL PATCH v9 3/3] xen/privcmd: Add new syscall to get gsi
from dev
On 23.09.24 09:58, Juergen Gross wrote:
> On 23.09.24 07:49, Chen, Jiqian wrote:
>> On 2024/9/21 05:17, Stefano Stabellini wrote:
>>> 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@....com>
>>>>>> Signed-off-by: Huang Rui <ray.huang@....com>
>>>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>
>>>>>> ---
>>>>>> 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@...el.com>
>>>>>> | Closes:
>>>>>> https://lore.kernel.org/oe-kbuild-all/202406090826.whl6Cb7R-lkp@intel.com/
>>>>>> ---
>>>>>> | Reported-by: kernel test robot <lkp@...el.com>
>>>>>> | Closes:
>>>>>> https://lore.kernel.org/oe-kbuild-all/202405171113.T431PC8O-lkp@intel.com/
>>>>>> ---
>>>>>> 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@intel.com/
>>>>
>>>> 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.
>> Using your attached .config, it also works for me.
>> The difference between your .config and the config reported by Robot
>> (https://download.01.org/0day-ci/archive/20240609/202406090826.whl6Cb7R-lkp@intel.com/config) is that your CONFIG_XEN_PRIVCMD=m, but Robot's CONFIG_XEN_PRIVCMD=y.
>>
>> It seems that, with my patch changes, privcmd uses the function implemented by
>> xen-pciback, so if the configuration is "CONFIG_XEN_PRIVCMD=m &
>> CONFIG_XEN_PCIDEV_BACKEND=m" or "CONFIG_XEN_PRIVCMD=y &
>> CONFIG_XEN_PCIDEV_BACKEND=y", the compilation is OK, but if the configuration
>> is "CONFIG_XEN_PRIVCMD=y & CONFIG_XEN_PCIDEV_BACKEND=m", issue happens.
>>
>> You can change CONFIG_XEN_PRIVCMD from "m" to "y" in your .config, then you
>> will fail at:
>> ld: vmlinux.o: in function `privcmd_ioctl':
>> privcmd.c:(.text+0x665e42): undefined reference to `pcistub_get_gsi_from_sbdf'
>
> You can do:
>
> if (IS_REACHABLE(CONFIG_XEN_PCIDEV_BACKEND)) {
> rc = pcistub_get_gsi_from_sbdf(kdata.sbdf);
> if (rc < 0)
> return rc;
> }
>
> See Documentation/kbuild/kconfig-language.rst in the kernel source tree.
Oh, I think this will need:
imply CONFIG_XEN_PCIDEV_BACKEND
in the CONFIG_XEN_PRIVCMD Kconfig definition.
Juergen
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