xen/vgic: Implement write to ISPENDR in vGICv{2, 3}

Currently, Xen will send a data abort to a guest trying to write to the
ISPENDR.

Unfortunately, recent version of Linux (at least 5.9+) will start
writing to the register if the interrupt needs to be re-triggered
(see the callback irq_retrigger). This can happen when a driver (such as
the xgbe network driver on AMD Seattle) re-enable an interrupt:

(XEN) d0v0: vGICD: unhandled word write 0x00000004000000 to ISPENDR44
[...]
[   25.635837] Unhandled fault at 0xffff80001000522c
[...]
[   25.818716]  gic_retrigger+0x2c/0x38
[   25.822361]  irq_startup+0x78/0x138
[   25.825920]  __enable_irq+0x70/0x80
[   25.829478]  enable_irq+0x50/0xa0
[   25.832864]  xgbe_one_poll+0xc8/0xd8
[   25.836509]  net_rx_action+0x110/0x3a8
[   25.840328]  __do_softirq+0x124/0x288
[   25.844061]  irq_exit+0xe0/0xf0
[   25.847272]  __handle_domain_irq+0x68/0xc0
[   25.851442]  gic_handle_irq+0xa8/0xe0
[   25.855171]  el1_irq+0xb0/0x180
[   25.858383]  arch_cpu_idle+0x18/0x28
[   25.862028]  default_idle_call+0x24/0x5c
[   25.866021]  do_idle+0x204/0x278
[   25.869319]  cpu_startup_entry+0x24/0x68
[   25.873313]  rest_init+0xd4/0xe4
[   25.876611]  arch_call_rest_init+0x10/0x1c
[   25.880777]  start_kernel+0x5b8/0x5ec

As a consequence, the OS may become unusable.

Implementing the write part of ISPENDR is somewhat easy. For
virtual interrupt, we only need to inject the interrupt again.

For physical interrupt, we need to be more careful as the de-activation
of the virtual interrupt will be propagated to the physical distributor.
For simplicity, the physical interrupt will be set pending so the
workflow will not differ from a "real" interrupt.

Longer term, we could possible directly activate the physical interrupt
and avoid taking an exception to inject the interrupt to the domain.
(This is the approach taken by the new vGIC based on KVM).

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index 64b141fea58602a504f83ad955b8dde69b98e220..b2da886adc183ff384550f0d4db75aab5e32cc7a 100644 (file)
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -472,10 +472,12 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info,
 
     case VRANGE32(GICD_ISPENDR, GICD_ISPENDRN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
-        printk(XENLOG_G_ERR
-               "%pv: vGICD: unhandled word write %#"PRIregister" to ISPENDR%d\n",
-               v, r, gicd_reg - GICD_ISPENDR);
-        return 0;
+        rank = vgic_rank_offset(v, 1, gicd_reg - GICD_ISPENDR, DABT_WORD);
+        if ( rank == NULL ) goto write_ignore;
+
+        vgic_set_irqs_pending(v, r, rank->index);
+
+        return 1;
 
     case VRANGE32(GICD_ICPENDR, GICD_ICPENDRN):
         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 fd8cfc156d0c5b3c67f21c7f6eece88d3e067b4b..613f37abab5e1bbe22a69e14acae666fa3f34a7a 100644 (file)
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -808,10 +808,12 @@ static int __vgic_v3_distr_common_mmio_write(const char *name, struct vcpu *v,
 
     case VRANGE32(GICD_ISPENDR, GICD_ISPENDRN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
-        printk(XENLOG_G_ERR
-               "%pv: %s: unhandled word write %#"PRIregister" to ISPENDR%d\n",
-               v, name, r, reg - GICD_ISPENDR);
-        return 0;
+        rank = vgic_rank_offset(v, 1, reg - GICD_ISPENDR, DABT_WORD);
+        if ( rank == NULL ) goto write_ignore;
+
+        vgic_set_irqs_pending(v, r, rank->index);
+
+        return 1;
 
     case VRANGE32(GICD_ICPENDR, GICD_ICPENDRN):
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -975,6 +977,7 @@ static int vgic_v3_rdistr_sgi_mmio_write(struct vcpu *v, mmio_info_t *info,
     case VREG32(GICR_ICACTIVER0):
     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
@@ -982,13 +985,6 @@ static int vgic_v3_rdistr_sgi_mmio_write(struct vcpu *v, mmio_info_t *info,
         return __vgic_v3_distr_common_mmio_write("vGICR: SGI", v,
                                                  info, gicr_reg, r);
 
-    case VREG32(GICR_ISPENDR0):
-        if ( dabt.size != DABT_WORD ) goto bad_width;
-        printk(XENLOG_G_ERR
-               "%pv: vGICR: SGI: unhandled word write %#"PRIregister" to ISPENDR0\n",
-               v, r);
-        return 0;
-
     case VREG32(GICR_ICPENDR0):
         if ( dabt.size != DABT_WORD ) goto bad_width;
         printk(XENLOG_G_ERR

diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 82f524a35c9eedf1c65f0b152e80ce49b1242a23..8f9400a51960d31d2b393b57e696457bc242a79d 100644 (file)
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -423,6 +423,53 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
     }
 }
 
+void vgic_set_irqs_pending(struct vcpu *v, uint32_t r, unsigned int rank)
+{
+    const unsigned long mask = r;
+    unsigned int i;
+    /* The first rank is always per-vCPU */
+    bool private = rank == 0;
+
+    /* LPIs will never be set pending via this function */
+    ASSERT(!is_lpi(32 * rank + 31));
+
+    for_each_set_bit( i, &mask, 32 )
+    {
+        unsigned int irq = i + 32 * rank;
+
+        if ( !private )
+        {
+            struct pending_irq *p = spi_to_pending(v->domain, irq);
+
+            /*
+             * When the domain sets the pending state for a HW interrupt on
+             * the virtual distributor, we set the pending state on the
+             * physical distributor.
+             *
+             * XXX: Investigate whether we would be able to set the
+             * physical interrupt active and save an interruption. (This
+             * is what the new vGIC does).
+             */
+            if ( p->desc != NULL )
+            {
+                unsigned long flags;
+
+                spin_lock_irqsave(&p->desc->lock, flags);
+                gic_set_pending_state(p->desc, true);
+                spin_unlock_irqrestore(&p->desc->lock, flags);
+                continue;
+            }
+        }
+
+        /*
+         * If the interrupt is per-vCPU, then we want to inject the vIRQ
+         * to v, otherwise we should let the function figuring out the
+         * correct vCPU.
+         */
+        vgic_inject_irq(v->domain, private ? v : NULL, irq, true);
+    }
+}
+
 bool vgic_to_sgi(struct vcpu *v, register_t sgir, enum gic_sgi_mode irqmode,
                  int virq, const struct sgi_target *target)
 {

diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
index ce1e3c4bbdac8a0d7316ce8ed1bda6ea9efd31dd..62c2ae538db2176f079a77122f463563dcb3cbaf 100644 (file)
--- a/xen/include/asm-arm/vgic.h
+++ b/xen/include/asm-arm/vgic.h
@@ -288,6 +288,8 @@ extern struct vgic_irq_rank *vgic_rank_offset(struct vcpu *v, int b, int n, int
 extern struct vgic_irq_rank *vgic_rank_irq(struct vcpu *v, unsigned int irq);
 extern void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n);
 extern void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n);
+extern void vgic_set_irqs_pending(struct vcpu *v, uint32_t r,
+                                  unsigned int rank);
 extern void register_vgic_ops(struct domain *d, const struct vgic_ops *ops);
 int vgic_v2_init(struct domain *d, int *mmio_count);
 int vgic_v3_init(struct domain *d, int *mmio_count);