x86/irq: allow setting IRQ permissions from GSI instead of pIRQ

Some domains are not aware of the pIRQ abstraction layer that maps
interrupt sources into Xen space interrupt numbers.  pIRQs values are
only exposed to domains that have the option to route physical
interrupts over event channels.

This creates issues for PCI-passthrough from a PVH domain, as some of
the passthrough related hypercalls use pIRQ as references to physical
interrupts on the system.  One of such interfaces is
XEN_DOMCTL_irq_permission, used to grant or revoke access to
interrupts, takes a pIRQ as the reference to the interrupt to be
adjusted.

Since PVH doesn't manage interrupts in terms of pIRQs, introduce a new
hypercall that allows setting interrupt permissions based on GSI value
rather than pIRQ.

Note the GSI hypercall parameters is translated to an IRQ value (in
case there are ACPI overrides) before doing the checks.

Signed-off-by: Jiqian Chen <[email protected]>
Signed-off-by: Huang Rui <[email protected]>
Signed-off-by: Jiqian Chen <[email protected]>
Reviewed-by: Daniel P. Smith <[email protected]>
Acked-by: Jan Beulich <[email protected]>

xen/arch/x86/domctl.c

@@ -36,6 +36,7 @@
 #include <asm/xstate.h>
 #include <asm/psr.h>
 #include <asm/cpu-policy.h>
+#include <asm/io_apic.h>
 
 static int update_domain_cpu_policy(struct domain *d,
                                     xen_domctl_cpu_policy_t *xdpc)
@@ -237,6 +238,37 @@ long arch_do_domctl(
         break;
     }
 
+    case XEN_DOMCTL_gsi_permission:
+    {
+        int irq;
+        unsigned int gsi = domctl->u.gsi_permission.gsi;
+        uint32_t flags = domctl->u.gsi_permission.flags;
+
+        /* Check only valid bits are set */
+        ret = -EINVAL;
+        if ( flags & ~XEN_DOMCTL_GSI_ACTION_MASK )
+            break;
+
+        irq = gsi_2_irq(gsi);
+        if ( irq <= 0 )
+        {
+            ret = irq ?: -EACCES;
+            break;
+        }
+
+        ret = -EPERM;
+        if ( !irq_access_permitted(currd, irq) ||
+             xsm_irq_permission(XSM_HOOK, d, irq, flags) )
+            break;
+
+        if ( flags )
+            ret = irq_permit_access(d, irq);
+        else
+            ret = irq_deny_access(d, irq);
+
+        break;
+    }
+
     case XEN_DOMCTL_getpageframeinfo3:
     {
         unsigned int num = domctl->u.getpageframeinfo3.num;

xen/arch/x86/include/asm/io_apic.h

@@ -213,5 +213,7 @@ unsigned highest_gsi(void);
 
 int ioapic_guest_read( unsigned long physbase, unsigned int reg, u32 *pval);
 int ioapic_guest_write(unsigned long physbase, unsigned int reg, u32 val);
+int mp_find_ioapic(unsigned int gsi);
+int gsi_2_irq(unsigned int gsi);
 
 #endif

xen/arch/x86/io_apic.c

@@ -955,6 +955,25 @@ static int pin_2_irq(int idx, int apic, int pin)
     return irq;
 }
 
+int gsi_2_irq(unsigned int gsi)
+{
+    int ioapic, irq;
+    unsigned int pin;
+
+    if ( gsi > highest_gsi() )
+        return -ERANGE;
+
+    ioapic = mp_find_ioapic(gsi);
+    if ( ioapic < 0 )
+        return -EINVAL;
+
+    pin = gsi - io_apic_gsi_base(ioapic);
+
+    irq = apic_pin_2_gsi_irq(ioapic, pin);
+
+    return irq ?: -EINVAL;
+}
+
 static inline int IO_APIC_irq_trigger(int irq)
 {
     int apic, idx, pin;

xen/arch/x86/mpparse.c

@@ -842,8 +842,7 @@ static struct mp_ioapic_routing {
 } mp_ioapic_routing[MAX_IO_APICS];
 
 
-static int mp_find_ioapic (
-	int			gsi)
+int mp_find_ioapic(unsigned int gsi)
 {
 	unsigned int		i;
 
@@ -854,7 +853,7 @@ static int mp_find_ioapic (
 			return i;
 	}
 
-	printk(KERN_ERR "ERROR: Unable to locate IOAPIC for GSI %d\n", gsi);
+	printk(KERN_ERR "ERROR: Unable to locate IOAPIC for GSI %u\n", gsi);
 
 	return -1;
 }
@@ -915,7 +914,7 @@ void __init mp_register_ioapic (
 	return;
 }
 
-unsigned __init highest_gsi(void)
+unsigned highest_gsi(void)
 {
 	unsigned x, res = 0;
 	for (x = 0; x < nr_ioapics; x++)

xen/include/public/domctl.h

@@ -464,6 +464,14 @@ struct xen_domctl_irq_permission {
     uint8_t pad[3];
 };
 
+/* XEN_DOMCTL_gsi_permission */
+struct xen_domctl_gsi_permission {
+    uint32_t gsi;
+#define XEN_DOMCTL_GSI_REVOKE      0
+#define XEN_DOMCTL_GSI_GRANT       1
+#define XEN_DOMCTL_GSI_ACTION_MASK 1
+    uint32_t flags;
+};
 
 /* XEN_DOMCTL_iomem_permission */
 struct xen_domctl_iomem_permission {
@@ -1306,6 +1314,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_get_paging_mempool_size       85
 #define XEN_DOMCTL_set_paging_mempool_size       86
 #define XEN_DOMCTL_dt_overlay                    87
+#define XEN_DOMCTL_gsi_permission                88
 #define XEN_DOMCTL_gdbsx_guestmemio            1000
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
@@ -1328,6 +1337,7 @@ struct xen_domctl {
         struct xen_domctl_setdomainhandle   setdomainhandle;
         struct xen_domctl_setdebugging      setdebugging;
         struct xen_domctl_irq_permission    irq_permission;
+        struct xen_domctl_gsi_permission    gsi_permission;
         struct xen_domctl_iomem_permission  iomem_permission;
         struct xen_domctl_ioport_permission ioport_permission;
         struct xen_domctl_hypercall_init    hypercall_init;

xen/xsm/flask/hooks.c

@@ -695,6 +695,7 @@ static int cf_check flask_domctl(struct domain *d, unsigned int cmd,
     case XEN_DOMCTL_shadow_op:
     case XEN_DOMCTL_ioport_permission:
     case XEN_DOMCTL_ioport_mapping:
+    case XEN_DOMCTL_gsi_permission:
 #endif
 #ifdef CONFIG_HAS_PASSTHROUGH
     /*