[PATCH v2] xen/arm: vgic to ignore GICD ICPENRn 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://lists.xenproject.org/archives/html/xen-devel/2021-09/
msg00744.html

Signed-off-by: Hongda Deng <hongda.deng@xxxxxxx>
---
 xen/arch/arm/vgic-v2.c | 26 +++++++++++++++++++++++++-
 xen/arch/arm/vgic-v3.c | 40 +++++++++++++++++++++++++++++++---------
 2 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index b2da886adc..d7ffaeeb65 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -480,11 +480,35 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info,
         return 1;
 
     case VRANGE32(GICD_ICPENDR, GICD_ICPENDRN):
+    {
+        struct pending_irq *iter;
+        unsigned int irq_start;
+        unsigned int irq_end;
+        uint32_t irq_pending = 0;
+
         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;
+
+        irq_start = (gicd_reg - GICD_ICPENDR) * 32;
+        irq_end = irq_start + 31;
+        /* go through inflight_irqs and print specified pending irqs */
+        list_for_each_entry(iter, &v->arch.vgic.inflight_irqs, inflight)
+        {
+            if ( iter->irq < irq_start || irq_end < iter->irq )
+                continue;
+
+            if ( test_bit(GIC_IRQ_GUEST_QUEUED, &iter->status) )
+                irq_pending = irq_pending | (1 << (iter->irq - irq_start));
+        }
+
+        if ( irq_pending != 0 )
+            printk(XENLOG_G_ERR
+                   "%pv: vGICD: ICPENDR%d=0x%08x\n",
+                   v, gicd_reg - GICD_ICPENDR, irq_pending);
+        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..243b24e496 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -816,11 +816,35 @@ static int __vgic_v3_distr_common_mmio_write(const char 
*name, struct vcpu *v,
         return 1;
 
     case VRANGE32(GICD_ICPENDR, GICD_ICPENDRN):
+    {
+        struct pending_irq *iter;
+        unsigned int irq_start;
+        unsigned int irq_end;
+        uint32_t irq_pending = 0;
+
         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;
+
+        irq_start = (reg - GICD_ICPENDR) * 32;
+        irq_end = irq_start + 31;
+        /* go through inflight_irqs and print specified pending irqs */
+        list_for_each_entry(iter, &v->arch.vgic.inflight_irqs, inflight)
+        {
+            if ( iter->irq < irq_start || irq_end < iter->irq )
+                continue;
+
+            if ( test_bit(GIC_IRQ_GUEST_QUEUED, &iter->status) )
+                irq_pending = irq_pending | (1 << (iter->irq - irq_start));
+        }
+
+        if ( irq_pending != 0 )
+            printk(XENLOG_G_ERR
+                   "%pv: %s: ICPENDR%d=0x%08x\n",
+                   v, name, reg - GICD_ICPENDR, irq_pending);
+        goto write_ignore_32;
+    }
 
     case VRANGE32(GICD_ISACTIVER, GICD_ISACTIVERN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -978,19 +1002,17 @@ static int vgic_v3_rdistr_sgi_mmio_write(struct vcpu *v, 
mmio_info_t *info,
     case VREG32(GICR_ICFGR1):
     case VRANGE32(GICR_IPRIORITYR0, GICR_IPRIORITYR7):
     case VREG32(GICR_ISPENDR0):
-         /*
-          * Above registers offset are common with GICD.
-          * So handle common with GICD handling
-          */
+        /*
+        * Above registers offset are common with GICD.
+        * So handle common with GICD handling
+        */
         return __vgic_v3_distr_common_mmio_write("vGICR: SGI", v,
                                                  info, gicr_reg, r);
 
     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 */
-- 
2.17.1