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Message-ID: <1cc89abe-3744-4c35-9d78-070e58d6836a@suse.com>
Date: Mon, 23 Sep 2024 09:58:13 +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 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.
Juergen
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