ARM: GICv3: forward pending LPIs to guests

Upon receiving an LPI on the host, we need to find the right VCPU and
virtual IRQ number to get this IRQ injected.
Iterate our two-level LPI table to find the domain ID and the virtual
LPI number quickly when the host takes an LPI. We then look up the
right VCPU in the struct pending_irq.
We use the existing injection function to let the GIC emulation deal
with this interrupt.
This introduces a do_LPI() as a hardware gic_ops.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
index 270a1362ec030861555f316c9621ebd18215b9f6..ffbe47c5d44e2b9ea27c837c4860795311a7d32a 100644 (file)
--- a/xen/arch/arm/gic-v2.c
+++ b/xen/arch/arm/gic-v2.c
@@ -1217,6 +1217,12 @@ static int __init gicv2_init(void)
     return 0;
 }
 
+static void gicv2_do_LPI(unsigned int lpi)
+{
+    /* No LPIs in a GICv2 */
+    BUG();
+}
+
 const static struct gic_hw_operations gicv2_ops = {
     .info                = &gicv2_info,
     .init                = gicv2_init,
@@ -1244,6 +1250,7 @@ const static struct gic_hw_operations gicv2_ops = {
     .make_hwdom_madt     = gicv2_make_hwdom_madt,
     .map_hwdom_extra_mappings = gicv2_map_hwdown_extra_mappings,
     .iomem_deny_access   = gicv2_iomem_deny_access,
+    .do_LPI              = gicv2_do_LPI,
 };
 
 /* Set up the GIC */

diff --git a/xen/arch/arm/gic-v3-lpi.c b/xen/arch/arm/gic-v3-lpi.c
index dbaf45ae15d21534fe9869a4937861a79bd21672..dc936fae725320c659c6d8e5ad69ac12f576a66d 100644 (file)
--- a/xen/arch/arm/gic-v3-lpi.c
+++ b/xen/arch/arm/gic-v3-lpi.c
@@ -136,6 +136,85 @@ uint64_t gicv3_get_redist_address(unsigned int cpu, bool use_pta)
         return per_cpu(lpi_redist, cpu).redist_id << 16;
 }
 
+void vgic_vcpu_inject_lpi(struct domain *d, unsigned int virq)
+{
+    /*
+     * TODO: this assumes that the struct pending_irq stays valid all of
+     * the time. We cannot properly protect this with the current locking
+     * scheme, but the future per-IRQ lock will solve this problem.
+     */
+    struct pending_irq *p = irq_to_pending(d->vcpu[0], virq);
+    unsigned int vcpu_id;
+
+    if ( !p )
+        return;
+
+    vcpu_id = ACCESS_ONCE(p->lpi_vcpu_id);
+    if ( vcpu_id >= d->max_vcpus )
+          return;
+
+    vgic_vcpu_inject_irq(d->vcpu[vcpu_id], virq);
+}
+
+/*
+ * Handle incoming LPIs, which are a bit special, because they are potentially
+ * numerous and also only get injected into guests. Treat them specially here,
+ * by just looking up their target vCPU and virtual LPI number and hand it
+ * over to the injection function.
+ * Please note that LPIs are edge-triggered only, also have no active state,
+ * so spurious interrupts on the host side are no issue (we can just ignore
+ * them).
+ * Also a guest cannot expect that firing interrupts that haven't been
+ * fully configured yet will reach the CPU, so we don't need to care about
+ * this special case.
+ */
+void gicv3_do_LPI(unsigned int lpi)
+{
+    struct domain *d;
+    union host_lpi *hlpip, hlpi;
+
+    irq_enter();
+
+    /* EOI the LPI already. */
+    WRITE_SYSREG32(lpi, ICC_EOIR1_EL1);
+
+    /* Find out if a guest mapped something to this physical LPI. */
+    hlpip = gic_get_host_lpi(lpi);
+    if ( !hlpip )
+        goto out;
+
+    hlpi.data = read_u64_atomic(&hlpip->data);
+
+    /*
+     * Unmapped events are marked with an invalid LPI ID. We can safely
+     * ignore them, as they have no further state and no-one can expect
+     * to see them if they have not been mapped.
+     */
+    if ( hlpi.virt_lpi == INVALID_LPI )
+        goto out;
+
+    d = rcu_lock_domain_by_id(hlpi.dom_id);
+    if ( !d )
+        goto out;
+
+    /*
+     * TODO: Investigate what to do here for potential interrupt storms.
+     * As we keep all host LPIs enabled, for disabling LPIs we would need
+     * to queue a ITS host command, which we avoid so far during a guest's
+     * runtime. Also re-enabling would trigger a host command upon the
+     * guest sending a command, which could be an attack vector for
+     * hogging the host command queue.
+     * See the thread around here for some background:
+     * https://lists.xen.org/archives/html/xen-devel/2016-12/msg00003.html
+     */
+    vgic_vcpu_inject_lpi(d, hlpi.virt_lpi);
+
+    rcu_unlock_domain(d);
+
+out:
+    irq_exit();
+}
+
 static int gicv3_lpi_allocate_pendtable(uint64_t *reg)
 {
     uint64_t val;

diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
index fc3614efee0699b2737fa32b32210ab02d196704..d539d6c85d32ca110d40d58edb2ee2e58a61bd39 100644 (file)
--- a/xen/arch/arm/gic-v3.c
+++ b/xen/arch/arm/gic-v3.c
@@ -1692,6 +1692,7 @@ static const struct gic_hw_operations gicv3_ops = {
     .make_hwdom_dt_node  = gicv3_make_hwdom_dt_node,
     .make_hwdom_madt     = gicv3_make_hwdom_madt,
     .iomem_deny_access   = gicv3_iomem_deny_access,
+    .do_LPI              = gicv3_do_LPI,
 };
 
 static int __init gicv3_dt_preinit(struct dt_device_node *node, const void *data)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index e1dfd66c48b44d8b52c96cb0f696391e95c8406a..9d473d7f2a1102f1a64c41e5ac077485ac638c60 100644 (file)
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -732,7 +732,13 @@ void gic_interrupt(struct cpu_user_regs *regs, int is_fiq)
             do_IRQ(regs, irq, is_fiq);
             local_irq_disable();
         }
-        else if (unlikely(irq < 16))
+        else if ( is_lpi(irq) )
+        {
+            local_irq_enable();
+            gic_hw_ops->do_LPI(irq);
+            local_irq_disable();
+        }
+        else if ( unlikely(irq < 16) )
         {
             do_sgi(regs, irq);
         }

diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 3d8e84c45e1f190d0009d26a00c33901c54d09a1..ebaea35ce542abcddd4606c16bfad4eccbd7ca54 100644 (file)
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -260,7 +260,8 @@ struct arch_vcpu
 
         /* GICv3: redistributor base and flags for this vCPU */
         paddr_t rdist_base;
-#define VGIC_V3_RDIST_LAST  (1 << 0)        /* last vCPU of the rdist */
+#define VGIC_V3_RDIST_LAST      (1 << 0)        /* last vCPU of the rdist */
+#define VGIC_V3_LPIS_ENABLED    (1 << 1)
         uint8_t flags;
     } vgic;
 

diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 7b2e98c82b4cd2695e275d185a3e2bd710b00898..6203dc59f4ad584bb3475a7e4ed1453dfc16343b 100644 (file)
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -367,6 +367,8 @@ struct gic_hw_operations {
     int (*map_hwdom_extra_mappings)(struct domain *d);
     /* Deny access to GIC regions */
     int (*iomem_deny_access)(const struct domain *d);
+    /* Handle LPIs, which require special handling */
+    void (*do_LPI)(unsigned int lpi);
 };
 
 void register_gic_ops(const struct gic_hw_operations *ops);

diff --git a/xen/include/asm-arm/gic_v3_its.h b/xen/include/asm-arm/gic_v3_its.h
index 29559a336cbb95c5a2d0a785215eb9da2f24475b..a659184dea11763e90e9b18adebd5059d457eec2 100644 (file)
--- a/xen/include/asm-arm/gic_v3_its.h
+++ b/xen/include/asm-arm/gic_v3_its.h
@@ -134,6 +134,8 @@ void gicv3_its_dt_init(const struct dt_device_node *node);
 
 bool gicv3_its_host_has_its(void);
 
+void gicv3_do_LPI(unsigned int lpi);
+
 int gicv3_lpi_init_rdist(void __iomem * rdist_base);
 
 /* Initialize the host structures for LPIs and the host ITSes. */
@@ -164,6 +166,8 @@ int gicv3_its_map_guest_device(struct domain *d,
 int gicv3_allocate_host_lpi_block(struct domain *d, uint32_t *first_lpi);
 void gicv3_free_host_lpi_block(uint32_t first_lpi);
 
+void vgic_vcpu_inject_lpi(struct domain *d, unsigned int virq);
+
 #else
 
 static inline void gicv3_its_dt_init(const struct dt_device_node *node)
@@ -175,6 +179,12 @@ static inline bool gicv3_its_host_has_its(void)
     return false;
 }
 
+static inline void gicv3_do_LPI(unsigned int lpi)
+{
+    /* We don't enable LPIs without an ITS. */
+    BUG();
+}
+
 static inline int gicv3_lpi_init_rdist(void __iomem * rdist_base)
 {
     return -ENODEV;