Re: [RFC KERNEL PATCH v6 3/3] xen/privcmd: Add new syscall to get gsi from irq

["Chen, Jiqian" <Jiqian.Chen@xxxxxxx>]

Hi,

On 2024/5/10 14:46, Jürgen Groß wrote:
> On 19.04.24 05:36, 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,
>> it causes the irq number is not equal with the gsi number.
>> And when passthrough a device, QEMU will use device's gsi
>> number to do pirq mapping, but the gsi number is got from
>> file /sys/bus/pci/devices/<sbdf>/irq, irq!= gsi, so it will
>> fail when mapping.
>> And in current linux codes, there is no method to translate
>> irq to gsi for userspace.
>>
>> For above purpose, record the relationship of gsi and irq
>> when PVH dom0 do acpi_register_gsi_ioapic for devices and
>> adds a new syscall into privcmd to let userspace can get
>> that translation when they have a need.
>>
>> Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
>> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
>> ---
>>   arch/x86/include/asm/apic.h      |  8 +++++++
>>   arch/x86/include/asm/xen/pci.h   |  5 ++++
>>   arch/x86/kernel/acpi/boot.c      |  2 +-
>>   arch/x86/pci/xen.c               | 21 +++++++++++++++++
>>   drivers/xen/events/events_base.c | 39 ++++++++++++++++++++++++++++++++
>>   drivers/xen/privcmd.c            | 19 ++++++++++++++++
>>   include/uapi/xen/privcmd.h       |  7 ++++++
>>   include/xen/events.h             |  5 ++++
>>   8 files changed, 105 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
>> index 9d159b771dc8..dd4139250895 100644
>> --- a/arch/x86/include/asm/apic.h
>> +++ b/arch/x86/include/asm/apic.h
>> @@ -169,6 +169,9 @@ extern bool apic_needs_pit(void);
>>     extern void apic_send_IPI_allbutself(unsigned int vector);
>>   +extern int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
>> +                    int trigger, int polarity);
>> +
>>   #else /* !CONFIG_X86_LOCAL_APIC */
>>   static inline void lapic_shutdown(void) { }
>>   #define local_apic_timer_c2_ok        1
>> @@ -183,6 +186,11 @@ static inline void apic_intr_mode_init(void) { }
>>   static inline void lapic_assign_system_vectors(void) { }
>>   static inline void lapic_assign_legacy_vector(unsigned int i, bool r) { }
>>   static inline bool apic_needs_pit(void) { return true; }
>> +static inline int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
>> +                    int trigger, int polarity)
>> +{
>> +    return (int)gsi;
>> +}
>>   #endif /* !CONFIG_X86_LOCAL_APIC */
>>     #ifdef CONFIG_X86_X2APIC
>> diff --git a/arch/x86/include/asm/xen/pci.h b/arch/x86/include/asm/xen/pci.h
>> index 9015b888edd6..aa8ded61fc2d 100644
>> --- a/arch/x86/include/asm/xen/pci.h
>> +++ b/arch/x86/include/asm/xen/pci.h
>> @@ -5,6 +5,7 @@
>>   #if defined(CONFIG_PCI_XEN)
>>   extern int __init pci_xen_init(void);
>>   extern int __init pci_xen_hvm_init(void);
>> +extern int __init pci_xen_pvh_init(void);
>>   #define pci_xen 1
>>   #else
>>   #define pci_xen 0
>> @@ -13,6 +14,10 @@ static inline int pci_xen_hvm_init(void)
>>   {
>>       return -1;
>>   }
>> +static inline int pci_xen_pvh_init(void)
>> +{
>> +    return -1;
>> +}
>>   #endif
>>   #ifdef CONFIG_XEN_PV_DOM0
>>   int __init pci_xen_initial_domain(void);
>> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
>> index 85a3ce2a3666..72c73458c083 100644
>> --- a/arch/x86/kernel/acpi/boot.c
>> +++ b/arch/x86/kernel/acpi/boot.c
>> @@ -749,7 +749,7 @@ static int acpi_register_gsi_pic(struct device *dev, u32 
>> gsi,
>>   }
>>     #ifdef CONFIG_X86_LOCAL_APIC
>> -static int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
>> +int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
>>                       int trigger, int polarity)
>>   {
>>       int irq = gsi;
>> diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
>> index 652cd53e77f6..f056ab5c0a06 100644
>> --- a/arch/x86/pci/xen.c
>> +++ b/arch/x86/pci/xen.c
>> @@ -114,6 +114,21 @@ static int acpi_register_gsi_xen_hvm(struct device 
>> *dev, u32 gsi,
>>                    false /* no mapping of GSI to PIRQ */);
>>   }
>>   +static int acpi_register_gsi_xen_pvh(struct device *dev, u32 gsi,
>> +                    int trigger, int polarity)
>> +{
>> +    int irq;
>> +
>> +    irq = acpi_register_gsi_ioapic(dev, gsi, trigger, polarity);
>> +    if (irq < 0)
>> +        return irq;
>> +
>> +    if (xen_pvh_add_gsi_irq_map(gsi, irq) == -EEXIST)
>> +        printk(KERN_INFO "Already map the GSI :%u and IRQ: %d\n", gsi, irq);
>> +
>> +    return irq;
>> +}
>> +
>>   #ifdef CONFIG_XEN_PV_DOM0
>>   static int xen_register_gsi(u32 gsi, int triggering, int polarity)
>>   {
>> @@ -558,6 +573,12 @@ int __init pci_xen_hvm_init(void)
>>       return 0;
>>   }
>>   +int __init pci_xen_pvh_init(void)
>> +{
>> +    __acpi_register_gsi = acpi_register_gsi_xen_pvh;
> 
> No support for unregistering the gsi again?
__acpi_unregister_gsi is set in function acpi_set_irq_model_ioapic.
Maybe I need to use a new function to call acpi_unregister_gsi_ioapic and 
remove the mapping of irq and gsi from xen_irq_list_head ?

> 
>> +    return 0;
>> +}
>> +
>>   #ifdef CONFIG_XEN_PV_DOM0
>>   int __init pci_xen_initial_domain(void)
>>   {
>> diff --git a/drivers/xen/events/events_base.c 
>> b/drivers/xen/events/events_base.c
>> index 27553673e46b..80d4f7faac64 100644
>> --- a/drivers/xen/events/events_base.c
>> +++ b/drivers/xen/events/events_base.c
>> @@ -953,6 +953,43 @@ int xen_irq_from_gsi(unsigned gsi)
>>   }
>>   EXPORT_SYMBOL_GPL(xen_irq_from_gsi);
>>   +int xen_gsi_from_irq(unsigned irq)
>> +{
>> +    struct irq_info *info;
>> +
>> +    list_for_each_entry(info, &xen_irq_list_head, list) {
>> +        if (info->type != IRQT_PIRQ)
>> +            continue;
>> +
>> +        if (info->irq == irq)
>> +            return info->u.pirq.gsi;
>> +    }
>> +
>> +    return -1;
>> +}
>> +EXPORT_SYMBOL_GPL(xen_gsi_from_irq);
>> +
>> +int xen_pvh_add_gsi_irq_map(unsigned gsi, unsigned irq)
>> +{
>> +    int tmp_irq;
>> +    struct irq_info *info;
>> +
>> +    tmp_irq = xen_irq_from_gsi(gsi);
>> +    if (tmp_irq != -1)
>> +        return -EEXIST;
>> +
>> +    info = kzalloc(sizeof(*info), GFP_KERNEL);
>> +    if (info == NULL)
>> +        panic("Unable to allocate metadata for GSI%d\n", gsi);
> 
> Please don't kill the system here, just return -ENOMEM.
Will change in next version.

> 
>> +
>> +    info->type = IRQT_PIRQ;
I am considering whether I need to use a new type(like IRQT_GSI) here to 
distinguish with IRQT_PIRQ, because function restore_pirqs will process all 
IRQT_PIRQ.

>> +    info->irq = irq;
>> +    info->u.pirq.gsi = gsi;
>> +    list_add_tail(&info->list, &xen_irq_list_head);
> 
> I think you need some kind of locking to protect changing of the list against
> concurrent accesses.
OK, will add a lock in next version.

> 
>> +
>> +    return 0;
>> +}
>> +
>>   static void __unbind_from_irq(struct irq_info *info, unsigned int irq)
>>   {
>>       evtchn_port_t evtchn;
>> @@ -2295,6 +2332,8 @@ void __init xen_init_IRQ(void)
>>       xen_init_setup_upcall_vector();
>>       xen_alloc_callback_vector();
>>   +    if (xen_pvh_domain())
>> +        pci_xen_pvh_init();
>>         if (xen_hvm_domain()) {
>>           native_init_IRQ();
>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>> index 67dfa4778864..11feed529e1d 100644
>> --- a/drivers/xen/privcmd.c
>> +++ b/drivers/xen/privcmd.c
>> @@ -842,6 +842,21 @@ static long privcmd_ioctl_mmap_resource(struct file 
>> *file,
>>       return rc;
>>   }
>>   +static long privcmd_ioctl_gsi_from_irq(struct file *file, void __user 
>> *udata)
>> +{
>> +    struct privcmd_gsi_from_irq kdata;
>> +
>> +    if (copy_from_user(&kdata, udata, sizeof(kdata)))
>> +        return -EFAULT;
>> +
>> +    kdata.gsi = xen_gsi_from_irq(kdata.irq);
>> +
>> +    if (copy_to_user(udata, &kdata, sizeof(kdata)))
>> +        return -EFAULT;
>> +
>> +    return 0;
> 
> Shouldn't you return an error if xen_gsi_from_irq() returned -1?
Oh, will change in next version.

> 
> 
> Juergen

-- 
Best regards,
Jiqian Chen.