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Date: Mon, 13 May 2024 09:59:34 +0200
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Subject: Re: [RFC KERNEL PATCH v6 3/3] xen/privcmd: Add new syscall to get gsi
 from irq
To: "Chen, Jiqian" <Jiqian.Chen@amd.com>,
 Stefano Stabellini <sstabellini@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
 "Rafael J . Wysocki" <rafael@kernel.org>,
 =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= <roger.pau@citrix.com>,
 "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
 "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
 "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
 "Huang, Ray" <Ray.Huang@amd.com>
References: <20240419033616.607889-1-Jiqian.Chen@amd.com>
 <20240419033616.607889-4-Jiqian.Chen@amd.com>
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On 13.05.24 09:47, Chen, Jiqian wrote:
> Hi,
> On 2024/5/10 17:06, Chen, Jiqian wrote:
>> 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@amd.com>
>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>>> ---
>>>>    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 ?
> When I tried to support unregistering the gsi and removing the mapping during disable device,
> I encountered that after running "xl pci-assignable-add 03:00.0", callstack pcistub_init_device->xen_pcibk_reset_device->pci_disable_device->pcibios_disable_device->acpi_pci_irq_disable->__acpi_unregister_gsi
> removed the mapping, after that when user space called xen_gsi_from_irq to get gsi, it failed.
> 
> To cover above case, I want to change the implementation of xen_gsi_from_irq to pass sbdf to get the gsi instead of passing irq,
> Because the sbdf and gsi of a device is unique and wiil not be changed even device is disabled or re-enabled.
> 
> Do you think this kind of change is acceptable?

Yes, I think so.


Juergen