ARM: GIC: extend LR read/write functions to cover EOI and source

So far our LR read/write functions do not handle the EOI bit and the
source CPUID bits in an LR, because the current VGIC implementation does
not use them.
Extend the gic_lr data structure to hold these bits of information by
using a union to differentiate field used depending on whether the vIRQ
has a corresponding pIRQ.

This allows the new VGIC to use this information.

This is based on the original patch sent by Andre Przywara [1].

[1] https://lists.xenproject.org/archives/html/xen-devel/2018-03/msg00435.html

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

xen/arch/arm/gic-v2.c

@@ -474,8 +474,17 @@ static void gicv2_read_lr(int lr, struct gic_lr *lr_reg)
 
     if ( lr_reg->hw_status )
     {
-        lr_reg->pirq = lrv >> GICH_V2_LR_PHYSICAL_SHIFT;
-        lr_reg->pirq &= GICH_V2_LR_PHYSICAL_MASK;
+        lr_reg->hw.pirq = lrv >> GICH_V2_LR_PHYSICAL_SHIFT;
+        lr_reg->hw.pirq &= GICH_V2_LR_PHYSICAL_MASK;
+    }
+    else
+    {
+        lr_reg->virt.eoi = (lrv & GICH_V2_LR_MAINTENANCE_IRQ);
+        if ( lr_reg->virq < NR_GIC_SGI )
+        {
+            lr_reg->virt.source = (lrv >> GICH_V2_LR_CPUID_SHIFT)
+                & GICH_V2_LR_CPUID_MASK;
+        }
     }
 }
 
@@ -496,7 +505,18 @@ static void gicv2_write_lr(int lr, const struct gic_lr *lr_reg)
     if ( lr_reg->hw_status )
     {
         lrv |= GICH_V2_LR_HW;
-        lrv |= lr_reg->pirq << GICH_V2_LR_PHYSICAL_SHIFT;
+        lrv |= lr_reg->hw.pirq << GICH_V2_LR_PHYSICAL_SHIFT;
+    }
+    else
+    {
+        if ( lr_reg->virt.eoi )
+            lrv |= GICH_V2_LR_MAINTENANCE_IRQ;
+        /*
+         * This is only valid for SGI, but it does not matter to always
+         * read it as it should be 0 by default.
+         */
+        ASSERT(!lr_reg->virt.source || lr_reg->virq < NR_GIC_SGI);
+        lrv |= (uint32_t)lr_reg->virt.source << GICH_V2_LR_CPUID_SHIFT;
     }
 
     writel_gich(lrv, GICH_LR + lr * 4);

xen/arch/arm/gic-v3.c

@@ -1014,12 +1014,25 @@ static void gicv3_read_lr(int lr, struct gic_lr *lr_reg)
     lr_reg->hw_status = lrv & ICH_LR_HW;
 
     if ( lr_reg->hw_status )
-        lr_reg->pirq = (lrv >> ICH_LR_PHYSICAL_SHIFT) & ICH_LR_PHYSICAL_MASK;
+        lr_reg->hw.pirq = (lrv >> ICH_LR_PHYSICAL_SHIFT) & ICH_LR_PHYSICAL_MASK;
+    else
+    {
+        lr_reg->virt.eoi = (lrv & ICH_LR_MAINTENANCE_IRQ);
+        /* Source only exists for SGI and in GICv2 compatible mode */
+        if ( lr_reg->virq < NR_GIC_SGI &&
+             current->domain->arch.vgic.version == GIC_V2 )
+        {
+            lr_reg->virt.source = (lrv >> ICH_LR_CPUID_SHIFT)
+                & ICH_LR_CPUID_MASK;
+        }
+    }
 }
 
 static void gicv3_write_lr(int lr_reg, const struct gic_lr *lr)
 {
     uint64_t lrv = 0;
+    const enum gic_version vgic_version = current->domain->arch.vgic.version;
+
 
     lrv = ( ((u64)(lr->virq & ICH_LR_VIRTUAL_MASK)  << ICH_LR_VIRTUAL_SHIFT) |
         ((u64)(lr->priority & ICH_LR_PRIORITY_MASK) << ICH_LR_PRIORITY_SHIFT) );
@@ -1033,14 +1046,29 @@ static void gicv3_write_lr(int lr_reg, const struct gic_lr *lr)
     if ( lr->hw_status )
     {
         lrv |= ICH_LR_HW;
-        lrv |= (uint64_t)lr->pirq << ICH_LR_PHYSICAL_SHIFT;
+        lrv |= (uint64_t)lr->hw.pirq << ICH_LR_PHYSICAL_SHIFT;
+    }
+    else
+    {
+        if ( lr->virt.eoi )
+            lrv |= ICH_LR_MAINTENANCE_IRQ;
+        /* Source is only set in GICv2 compatible mode */
+        if ( vgic_version == GIC_V2 )
+        {
+            /*
+             * This is only valid for SGI, but it does not matter to always
+             * read it as it should be 0 by default.
+             */
+            ASSERT(!lr->virt.source || lr->virq < NR_GIC_SGI);
+            lrv |= (uint64_t)lr->virt.source << ICH_LR_CPUID_SHIFT;
+        }
     }
 
     /*
      * When the guest is using vGICv3, all the IRQs are Group 1. Group 0
      * would result in a FIQ, which will not be expected by the guest OS.
      */
-    if ( current->domain->arch.vgic.version == GIC_V3 )
+    if ( vgic_version == GIC_V3 )
         lrv |= ICH_LR_GRP1;
 
     gicv3_ich_write_lr(lr_reg, lrv);

xen/include/asm-arm/gic.h

@@ -204,14 +204,26 @@ union gic_state_data {
  * The LR register format is different for GIC HW version
  */
 struct gic_lr {
-   /* Physical IRQ -> Only set when hw_status is set. */
-   uint32_t pirq;
    /* Virtual IRQ */
    uint32_t virq;
    uint8_t priority;
    bool active;
    bool pending;
    bool hw_status;
+   union
+   {
+       /* Only filled when there are a corresponding pIRQ (hw_state = true) */
+       struct
+       {
+           uint32_t pirq;
+       } hw;
+       /* Only filled when there are no corresponding pIRQ (hw_state = false) */
+       struct
+       {
+           bool eoi;
+           uint8_t source;      /* GICv2 only */
+       } virt;
+   };
 };
 
 enum gic_version {

xen/include/asm-arm/gic_v3_defs.h

@@ -167,6 +167,8 @@
 
 #define ICH_LR_VIRTUAL_MASK          0xffff
 #define ICH_LR_VIRTUAL_SHIFT         0
+#define ICH_LR_CPUID_MASK            0x7
+#define ICH_LR_CPUID_SHIFT           10
 #define ICH_LR_PHYSICAL_MASK         0x3ff
 #define ICH_LR_PHYSICAL_SHIFT        32
 #define ICH_LR_STATE_MASK            0x3