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[Xen-devel] [RFC PATCH v2 08/22] ARM: vGIC: move virtual IRQ priority from rank to pending_irq



So far a virtual interrupt's priority is stored in the irq_rank
structure, which covers multiple IRQs and has a single lock for this
group.
Generalize the already existing priority variable in struct pending_irq
to not only cover LPIs, but every IRQ. Access to this value is protected
by the per-IRQ lock.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 xen/arch/arm/vgic-v2.c     | 34 ++++++----------------------------
 xen/arch/arm/vgic-v3.c     | 36 ++++++++----------------------------
 xen/arch/arm/vgic.c        | 41 +++++++++++++++++------------------------
 xen/include/asm-arm/vgic.h | 10 ----------
 4 files changed, 31 insertions(+), 90 deletions(-)

diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index cf4ab89..ed7ff3b 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -171,6 +171,7 @@ static int vgic_v2_distr_mmio_read(struct vcpu *v, 
mmio_info_t *info,
     struct vgic_irq_rank *rank;
     int gicd_reg = (int)(info->gpa - v->domain->arch.vgic.dbase);
     unsigned long flags;
+    unsigned int irq;
 
     perfc_incr(vgicd_reads);
 
@@ -250,22 +251,10 @@ static int vgic_v2_distr_mmio_read(struct vcpu *v, 
mmio_info_t *info,
         goto read_as_zero;
 
     case VRANGE32(GICD_IPRIORITYR, GICD_IPRIORITYRN):
-    {
-        uint32_t ipriorityr;
-        uint8_t rank_index;
-
         if ( dabt.size != DABT_BYTE && dabt.size != DABT_WORD ) goto bad_width;
-        rank = vgic_rank_offset(v, 8, gicd_reg - GICD_IPRIORITYR, DABT_WORD);
-        if ( rank == NULL ) goto read_as_zero;
-        rank_index = REG_RANK_INDEX(8, gicd_reg - GICD_IPRIORITYR, DABT_WORD);
-
-        vgic_lock_rank(v, rank, flags);
-        ipriorityr = ACCESS_ONCE(rank->ipriorityr[rank_index]);
-        vgic_unlock_rank(v, rank, flags);
-        *r = vreg_reg32_extract(ipriorityr, info);
-
+        irq = gicd_reg - GICD_IPRIORITYR; /* 8 bit per IRQ, so IRQ = offset */
+        *r = vgic_fetch_irq_priority(v, irq, (dabt.size == DABT_BYTE) ? 1 : 4);
         return 1;
-    }
 
     case VREG32(0x7FC):
         goto read_reserved;
@@ -415,6 +404,7 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info,
     int gicd_reg = (int)(info->gpa - v->domain->arch.vgic.dbase);
     uint32_t tr;
     unsigned long flags;
+    unsigned int irq;
 
     perfc_incr(vgicd_writes);
 
@@ -498,23 +488,11 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info,
         goto write_ignore_32;
 
     case VRANGE32(GICD_IPRIORITYR, GICD_IPRIORITYRN):
-    {
-        uint32_t *ipriorityr, priority;
-
         if ( dabt.size != DABT_BYTE && dabt.size != DABT_WORD ) goto bad_width;
-        rank = vgic_rank_offset(v, 8, gicd_reg - GICD_IPRIORITYR, DABT_WORD);
-        if ( rank == NULL) goto write_ignore;
-        vgic_lock_rank(v, rank, flags);
-        ipriorityr = &rank->ipriorityr[REG_RANK_INDEX(8,
-                                                      gicd_reg - 
GICD_IPRIORITYR,
-                                                      DABT_WORD)];
-        priority = ACCESS_ONCE(*ipriorityr);
-        vreg_reg32_update(&priority, r, info);
-        ACCESS_ONCE(*ipriorityr) = priority;
 
-        vgic_unlock_rank(v, rank, flags);
+        irq = gicd_reg - GICD_IPRIORITYR; /* 8 bit per IRQ, so IRQ = offset */
+        vgic_store_irq_priority(v, (dabt.size == DABT_BYTE) ? 1 : 4, irq, r);
         return 1;
-    }
 
     case VREG32(0x7FC):
         goto write_reserved;
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index ad9019e..e58e77e 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -677,6 +677,7 @@ static int __vgic_v3_distr_common_mmio_read(const char 
*name, struct vcpu *v,
     struct hsr_dabt dabt = info->dabt;
     struct vgic_irq_rank *rank;
     unsigned long flags;
+    unsigned int irq;
 
     switch ( reg )
     {
@@ -714,23 +715,11 @@ static int __vgic_v3_distr_common_mmio_read(const char 
*name, struct vcpu *v,
         goto read_as_zero;
 
     case VRANGE32(GICD_IPRIORITYR, GICD_IPRIORITYRN):
-    {
-        uint32_t ipriorityr;
-        uint8_t rank_index;
-
         if ( dabt.size != DABT_BYTE && dabt.size != DABT_WORD ) goto bad_width;
-        rank = vgic_rank_offset(v, 8, reg - GICD_IPRIORITYR, DABT_WORD);
-        if ( rank == NULL ) goto read_as_zero;
-        rank_index = REG_RANK_INDEX(8, reg - GICD_IPRIORITYR, DABT_WORD);
-
-        vgic_lock_rank(v, rank, flags);
-        ipriorityr = ACCESS_ONCE(rank->ipriorityr[rank_index]);
-        vgic_unlock_rank(v, rank, flags);
-
-        *r = vreg_reg32_extract(ipriorityr, info);
-
+        irq = reg - GICD_IPRIORITYR; /* 8 bit per IRQ, so IRQ = offset */
+        if ( irq >= v->domain->arch.vgic.nr_spis + 32 ) goto read_as_zero;
+        *r = vgic_fetch_irq_priority(v, irq, (dabt.size == DABT_BYTE) ? 1 : 4);
         return 1;
-    }
 
     case VRANGE32(GICD_ICFGR, GICD_ICFGRN):
     {
@@ -774,6 +763,7 @@ static int __vgic_v3_distr_common_mmio_write(const char 
*name, struct vcpu *v,
     struct vgic_irq_rank *rank;
     uint32_t tr;
     unsigned long flags;
+    unsigned int irq;
 
     switch ( reg )
     {
@@ -831,21 +821,11 @@ static int __vgic_v3_distr_common_mmio_write(const char 
*name, struct vcpu *v,
         goto write_ignore_32;
 
     case VRANGE32(GICD_IPRIORITYR, GICD_IPRIORITYRN):
-    {
-        uint32_t *ipriorityr, priority;
-
         if ( dabt.size != DABT_BYTE && dabt.size != DABT_WORD ) goto bad_width;
-        rank = vgic_rank_offset(v, 8, reg - GICD_IPRIORITYR, DABT_WORD);
-        if ( rank == NULL ) goto write_ignore;
-        vgic_lock_rank(v, rank, flags);
-        ipriorityr = &rank->ipriorityr[REG_RANK_INDEX(8, reg - GICD_IPRIORITYR,
-                                                      DABT_WORD)];
-        priority = ACCESS_ONCE(*ipriorityr);
-        vreg_reg32_update(&priority, r, info);
-        ACCESS_ONCE(*ipriorityr) = priority;
-        vgic_unlock_rank(v, rank, flags);
+        irq = reg - GICD_IPRIORITYR; /* 8 bit per IRQ, so IRQ = offset */
+        if ( irq >= v->domain->arch.vgic.nr_spis + 32 ) goto write_ignore;
+        vgic_store_irq_priority(v, (dabt.size == DABT_BYTE) ? 1 : 4, irq, r);
         return 1;
-    }
 
     case VREG32(GICD_ICFGR): /* Restricted to configure SGIs */
         goto write_ignore_32;
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index b2c9632..ddcd99b 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -231,18 +231,6 @@ struct vcpu *vgic_get_target_vcpu(struct vcpu *v, unsigned 
int virq)
     return v->domain->vcpu[target];
 }
 
-static int vgic_get_virq_priority(struct vcpu *v, unsigned int virq)
-{
-    struct vgic_irq_rank *rank;
-
-    /* LPIs don't have a rank, also store their priority separately. */
-    if ( is_lpi(virq) )
-        return v->domain->arch.vgic.handler->lpi_get_priority(v->domain, virq);
-
-    rank = vgic_rank_irq(v, virq);
-    return ACCESS_ONCE(rank->priority[virq & INTERRUPT_RANK_MASK]);
-}
-
 #define MAX_IRQS_PER_IPRIORITYR 4
 uint32_t vgic_fetch_irq_priority(struct vcpu *v, unsigned int nrirqs,
                                  unsigned int first_irq)
@@ -567,37 +555,40 @@ void vgic_clear_pending_irqs(struct vcpu *v)
 
 void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int virq)
 {
-    uint8_t priority;
     struct pending_irq *iter, *n;
-    unsigned long flags;
+    unsigned long flags, vcpu_flags;
     bool running;
 
-    spin_lock_irqsave(&v->arch.vgic.lock, flags);
+    spin_lock_irqsave(&v->arch.vgic.lock, vcpu_flags);
 
     n = irq_to_pending(v, virq);
     /* If an LPI has been removed, there is nothing to inject here. */
     if ( unlikely(!n) )
     {
-        spin_unlock_irqrestore(&v->arch.vgic.lock, flags);
+        spin_unlock_irqrestore(&v->arch.vgic.lock, vcpu_flags);
         return;
     }
 
     /* vcpu offline */
     if ( test_bit(_VPF_down, &v->pause_flags) )
     {
-        spin_unlock_irqrestore(&v->arch.vgic.lock, flags);
+        spin_unlock_irqrestore(&v->arch.vgic.lock, vcpu_flags);
         return;
     }
 
+    vgic_irq_lock(n, flags);
+
     set_bit(GIC_IRQ_GUEST_QUEUED, &n->status);
 
     if ( !list_empty(&n->inflight) )
     {
         bool update = test_bit(GIC_IRQ_GUEST_ENABLED, &n->status) &&
                       list_empty(&n->lr_queue) && (v == current);
+        int lr = ACCESS_ONCE(n->lr);
 
+        vgic_irq_unlock(n, flags);
         if ( update )
-            gic_update_one_lr(v, n->lr);
+            gic_update_one_lr(v, lr);
 #ifdef GIC_DEBUG
         else
             gdprintk(XENLOG_DEBUG, "trying to inject irq=%u into d%dv%d, when 
it is still lr_pending\n",
@@ -606,24 +597,26 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int 
virq)
         goto out;
     }
 
-    priority = vgic_get_virq_priority(v, virq);
-    n->cur_priority = priority;
+    n->cur_priority = n->priority;
 
     /* the irq is enabled */
     if ( test_bit(GIC_IRQ_GUEST_ENABLED, &n->status) )
-        gic_raise_guest_irq(v, virq, priority);
+        gic_raise_guest_irq(v, virq, n->cur_priority);
 
     list_for_each_entry ( iter, &v->arch.vgic.inflight_irqs, inflight )
     {
-        if ( iter->cur_priority > priority )
+        if ( iter->cur_priority > n->cur_priority )
         {
             list_add_tail(&n->inflight, &iter->inflight);
-            goto out;
+            goto out_unlock_irq;
         }
     }
     list_add_tail(&n->inflight, &v->arch.vgic.inflight_irqs);
+
+out_unlock_irq:
+    vgic_irq_unlock(n, flags);
 out:
-    spin_unlock_irqrestore(&v->arch.vgic.lock, flags);
+    spin_unlock_irqrestore(&v->arch.vgic.lock, vcpu_flags);
     /* we have a new higher priority irq, inject it into the guest */
     running = v->is_running;
     vcpu_unblock(v);
diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
index f3791c8..59d52c6 100644
--- a/xen/include/asm-arm/vgic.h
+++ b/xen/include/asm-arm/vgic.h
@@ -113,16 +113,6 @@ struct vgic_irq_rank {
     uint32_t icfg[2];
 
     /*
-     * Provide efficient access to the priority of an vIRQ while keeping
-     * the emulation simple.
-     * Note, this is working fine as long as Xen is using little endian.
-     */
-    union {
-        uint8_t priority[32];
-        uint32_t ipriorityr[8];
-    };
-
-    /*
      * It's more convenient to store a target VCPU per vIRQ
      * than the register ITARGETSR/IROUTER itself.
      * Use atomic operations to read/write the vcpu fields to avoid
-- 
2.9.0


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