[PATCH v3] xen/arm: vgic to ignore GICD ICPENDRn registers access

[Hongda Deng <Hongda.Deng@xxxxxxx>]

Currently, Xen will return IO unhandled when guests access GICD ICPENRn
registers. This will raise a data abort inside guest. For Linux Guest,
these virtual registers will not be accessed. But for Zephyr, in its
GIC initialization code, these virtual registers will be accessed. And
zephyr guest will get an IO data abort in initilization stage and enter
fatal error. Emulating ICPENDR is not easy with the existing vGIC, so
we currently ignore these virtual registers access and print a message
about whether they are already pending instead of returning unhandled.
More details can be found at [1].

[1] https://github.com/zephyrproject-rtos/zephyr/blob/eaf6cf745df3807e6e
cc941c3a30de6c179ae359/drivers/interrupt_controller/intc_gicv3.c#L274

Signed-off-by: Hongda Deng <hongda.deng@xxxxxxx>
---
Changes since v2:
 *  Avoid to print messages when there is no pending interrupt
 *  Add helper vgic_check_inflight_irqs_pending to check pending status
 *  Print a message for each interrupt separately
Changes since v1:
 *  Check pending states by going through vcpu->arch.vgic.inflight_irqs
    instead of checking hardware registers
---
 xen/arch/arm/vgic-v2.c     | 10 ++++++----
 xen/arch/arm/vgic-v3.c     | 16 ++++++++--------
 xen/arch/arm/vgic.c        | 36 ++++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/vgic.h |  3 ++-
 4 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index b2da886adc..7c30da327c 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -481,10 +481,12 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info,
 
     case VRANGE32(GICD_ICPENDR, GICD_ICPENDRN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
-        printk(XENLOG_G_ERR
-               "%pv: vGICD: unhandled word write %#"PRIregister" to 
ICPENDR%d\n",
-               v, r, gicd_reg - GICD_ICPENDR);
-        return 0;
+        rank = vgic_rank_offset(v, 1, gicd_reg - GICD_ICPENDR, DABT_WORD);
+        if ( rank == NULL ) goto write_ignore;
+
+        vgic_check_inflight_irqs_pending(v->domain, v, rank->index, r);
+
+        goto write_ignore_32;
 
     case VRANGE32(GICD_ISACTIVER, GICD_ISACTIVERN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index cb5a70c42e..4913301d22 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -817,10 +817,12 @@ static int __vgic_v3_distr_common_mmio_write(const char 
*name, struct vcpu *v,
 
     case VRANGE32(GICD_ICPENDR, GICD_ICPENDRN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
-        printk(XENLOG_G_ERR
-               "%pv: %s: unhandled word write %#"PRIregister" to ICPENDR%d\n",
-               v, name, r, reg - GICD_ICPENDR);
-        return 0;
+        rank = vgic_rank_offset(v, 1, reg - GICD_ICPENDR, DABT_WORD);
+        if ( rank == NULL ) goto write_ignore;
+
+        vgic_check_inflight_irqs_pending(v->domain, v, rank->index, r);
+
+        goto write_ignore_32;
 
     case VRANGE32(GICD_ISACTIVER, GICD_ISACTIVERN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -987,10 +989,8 @@ static int vgic_v3_rdistr_sgi_mmio_write(struct vcpu *v, 
mmio_info_t *info,
 
     case VREG32(GICR_ICPENDR0):
         if ( dabt.size != DABT_WORD ) goto bad_width;
-        printk(XENLOG_G_ERR
-               "%pv: vGICR: SGI: unhandled word write %#"PRIregister" to 
ICPENDR0\n",
-               v, r);
-        return 0;
+        return __vgic_v3_distr_common_mmio_write("vGICR: SGI", v,
+                                                 info, gicr_reg, r);
 
     case VREG32(GICR_IGRPMODR0):
         /* We do not implement security extensions for guests, write ignore */
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 8f9400a519..0565557814 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -726,6 +726,42 @@ unsigned int vgic_max_vcpus(unsigned int 
domctl_vgic_version)
     }
 }
 
+void vgic_check_inflight_irqs_pending(struct domain *d, struct vcpu *v,
+                                      unsigned int rank, uint32_t r)
+{
+    const unsigned long mask = r;
+    unsigned int i;
+    unsigned long flags;
+    struct pending_irq *p;
+    bool private = rank == 0;
+    struct vcpu *v_target;
+
+    for_each_set_bit( i, &mask, 32 )
+    {
+        unsigned int irq = i + 32 * rank;
+
+        if ( private )
+            v_target = vgic_get_target_vcpu(v, irq);
+        else
+            v_target = vgic_get_target_vcpu(d->vcpu[0], irq);
+
+        spin_lock_irqsave(&v_target->arch.vgic.lock, flags);
+
+        p = irq_to_pending(v_target, irq);
+
+        if ( unlikely(!p) )
+        {
+            spin_unlock_irqrestore(&v_target->arch.vgic.lock, flags);
+            continue;
+        }
+
+        if ( !list_empty(&p->inflight) )
+            printk("%pv trying to clear pending interrupt %u.\n", v, irq);
+
+        spin_unlock_irqrestore(&v_target->arch.vgic.lock, flags);
+    }
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
index 62c2ae538d..abcaae2969 100644
--- a/xen/include/asm-arm/vgic.h
+++ b/xen/include/asm-arm/vgic.h
@@ -298,7 +298,8 @@ extern bool vgic_to_sgi(struct vcpu *v, register_t sgir,
                         enum gic_sgi_mode irqmode, int virq,
                         const struct sgi_target *target);
 extern bool vgic_migrate_irq(struct vcpu *old, struct vcpu *new, unsigned int 
irq);
-
+extern void vgic_check_inflight_irqs_pending(struct domain *d, struct vcpu *v,
+                                             unsigned int rank, uint32_t r);
 #endif /* !CONFIG_NEW_VGIC */
 
 /*** Common VGIC functions used by Xen arch code ****/
-- 
2.17.1