Re: [RFC PATCH 4/5] x86/xen: acpi registers gsi for xen pvh

[Roger Pau Monné]

On Sun, Mar 12, 2023 at 08:01:56PM +0800, Huang Rui wrote:
> From: Chen Jiqian 
> 
> Add acpi_register_gsi_xen_pvh() to register gsi for PVH mode.
> In addition to call acpi_register_gsi_ioapic(), it also setup
> a map between gsi and vector in hypervisor side. So that,
> when dgpu create an interrupt, hypervisor can correctly find
> which guest domain to process interrupt by vector.

The term 'dgpu' needs clarifying or replacing by a more generic
naming.

Also, I would like to be able to get away from requiring dom0 to
register the GSIs in this way.  If you take a look at Xen, there's
code in the emulated IO-APIC available to dom0 that already does this
registering (see vioapic_hwdom_map_gsi() in Xen).

I think the problem here is that the GSI used by the device you want
to passthrough has never had it's pin unmasked in the IO-APIC, and
hence hasn't been registered.

It would be helpful if you could state in the commit message what
issue you are trying to solve by doing this registering here, I assume
it is done in order to map the IRQ to a PIRQ, so later calls by the
toolstack to bind it succeed.

Would it be possible instead to perform the call to PHYSDEVOP_map_pirq
in the toolstack itself if the PIRQ cannot be found?

Thanks, Roger.

[RFC PATCH 4/5] x86/xen: acpi registers gsi for xen pvh

[Huang Rui]

From: Chen Jiqian 

Add acpi_register_gsi_xen_pvh() to register gsi for PVH mode.
In addition to call acpi_register_gsi_ioapic(), it also setup
a map between gsi and vector in hypervisor side. So that,
when dgpu create an interrupt, hypervisor can correctly find
which guest domain to process interrupt by vector.

Signed-off-by: Chen Jiqian 
Signed-off-by: Huang Rui 
---
 arch/x86/include/asm/apic.h  |  7 ++
 arch/x86/include/asm/xen/pci.h   |  5 
 arch/x86/kernel/acpi/boot.c  |  2 +-
 arch/x86/pci/xen.c   | 39 
 drivers/xen/events/events_base.c |  2 ++
 5 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 3415321c8240..f3bc5de1f1d4 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -179,6 +179,8 @@ 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
@@ -193,6 +195,11 @@ 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 907cc98b1938..25ec48dd897e 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -718,7 +718,7 @@ 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 b94f727251b6..43b8b6d7147b 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -114,6 +114,38 @@ 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;
+   int rc;
+   struct physdev_map_pirq map_irq;
+   struct physdev_setup_gsi setup_gsi;
+
+   irq = acpi_register_gsi_ioapic(dev, gsi, trigger, polarity);
+
+   map_irq.domid = DOMID_SELF;
+   map_irq.type = MAP_PIRQ_TYPE_GSI;
+   map_irq.index = gsi;
+   map_irq.pirq = gsi;
+
+   rc = HYPERVISOR_physdev_op(PHYSDEVOP_map_pirq, &map_irq);
+   if (rc)
+   printk(KERN_ERR "xen map GSI: %u failed %d\n", gsi, rc);
+
+   setup_gsi.gsi = gsi;
+   setup_gsi.triggering = (trigger == ACPI_EDGE_SENSITIVE ? 0 : 1);
+   setup_gsi.polarity = (polarity == ACPI_ACTIVE_HIGH ? 0 : 1);
+
+   rc = HYPERVISOR_physdev_op(PHYSDEVOP_setup_gsi, &setup_gsi);
+   if (rc == -EEXIST)
+   printk(KERN_INFO "Already setup the GSI :%u\n", gsi);
+   else if (rc)
+   printk(KERN_ERR "Failed to setup GSI :%u, err_code:%d\n", gsi, 
rc);
+
+   return irq;
+}
+
 #ifdef CONFIG_XEN_PV_DOM0
 static int xen_register_gsi(u32 gsi, int triggering, int polarity)
 {
@@ -554,6 +586,13 @@ int __init pci_xen_hvm_init(void)
return 0;
 }
 
+int __init pci_xen_pvh_init(void)
+{
+   __acpi_register_gsi = acpi_register_gsi_xen_pvh;
+   __acpi_unregister_gsi = NULL;
+   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 c443f04aaad7..48dff0ed9acd 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -2317,6 +2317,8 @@ void __init xen_init_IRQ(void)
xen_init_setup_upcall_vector();
xen_alloc_callback_vector();
 
+