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Re: [Xen-devel] [PATCH 1/7] xen/arm: fix rank calculation in vgic_vcpu_inject_irq



On Fri, 26 Oct 2012, Ian Campbell wrote:
> > It means that this patch hides the bug rather than fixing it...
> 
> What are the symptoms?
> 
> BTW I noticed that "byte = irq & 0x3;" is redundant since byte_read also
> has the & in it. But that won't cause problems.

The ienable bit is wrong for irq > 32.

I think that the problem is the usage of vgic_irq_rank with registers
that have 1 bit per interrupt.
In fact the following patch fixes the issue.

---


xen/arm: pass the correct bit-per-interrupt argument to vgic_irq_rank

Use 1 for registers that have 1 bit per irq.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 3c3983f..92731b6 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -42,13 +42,7 @@
  */
 static inline int REG_RANK_NR(int b, uint32_t n)
 {
-    switch ( b )
-    {
-    case 8: return n >> 3;
-    case 4: return n >> 2;
-    case 2: return n >> 1;
-    default: BUG();
-    }
+    return n / b;
 }
 
 /*
@@ -199,7 +193,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_ISENABLER ... GICD_ISENABLERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ISENABLER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ISENABLER);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = rank->ienable;
@@ -208,7 +202,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_ICENABLER ... GICD_ICENABLERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ICENABLER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ICENABLER);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = rank->ienable;
@@ -217,7 +211,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_ISPENDR ... GICD_ISPENDRN:
         if ( dabt.size != 0 && dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ISPENDR);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ISPENDR);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = byte_read(rank->ipend, dabt.sign, offset);
@@ -226,7 +220,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_ICPENDR ... GICD_ICPENDRN:
         if ( dabt.size != 0 && dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ICPENDR);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ICPENDR);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = byte_read(rank->ipend, dabt.sign, offset);
@@ -235,7 +229,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_ISACTIVER ... GICD_ISACTIVERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ISACTIVER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ISACTIVER);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = rank->iactive;
@@ -244,7 +238,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_ICACTIVER ... GICD_ICACTIVERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ICACTIVER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ICACTIVER);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = rank->iactive;
@@ -296,7 +290,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_CPENDSGIR ... GICD_CPENDSGIRN:
         if ( dabt.size != 0 && dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_CPENDSGIR);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_CPENDSGIR);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = byte_read(rank->pendsgi, dabt.sign, offset);
@@ -305,7 +299,7 @@ static int vgic_distr_mmio_read(struct vcpu *v, mmio_info_t 
*info)
 
     case GICD_SPENDSGIR ... GICD_SPENDSGIRN:
         if ( dabt.size != 0 && dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_SPENDSGIR);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_SPENDSGIR);
         if ( rank == NULL) goto read_as_zero;
         vgic_lock_rank(v, rank);
         *r = byte_read(rank->pendsgi, dabt.sign, offset);
@@ -400,7 +394,7 @@ static int vgic_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info)
 
     case GICD_ISENABLER ... GICD_ISENABLERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ISENABLER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ISENABLER);
         if ( rank == NULL) goto write_ignore;
         vgic_lock_rank(v, rank);
         tr = rank->ienable;
@@ -411,7 +405,7 @@ static int vgic_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info)
 
     case GICD_ICENABLER ... GICD_ICENABLERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ICENABLER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ICENABLER);
         if ( rank == NULL) goto write_ignore;
         vgic_lock_rank(v, rank);
         rank->ienable &= ~*r;
@@ -432,7 +426,7 @@ static int vgic_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info)
 
     case GICD_ISACTIVER ... GICD_ISACTIVERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ISACTIVER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ISACTIVER);
         if ( rank == NULL) goto write_ignore;
         vgic_lock_rank(v, rank);
         rank->iactive &= ~*r;
@@ -441,7 +435,7 @@ static int vgic_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info)
 
     case GICD_ICACTIVER ... GICD_ICACTIVERN:
         if ( dabt.size != 2 ) goto bad_width;
-        rank = vgic_irq_rank(v, 8, gicd_reg - GICD_ICACTIVER);
+        rank = vgic_irq_rank(v, 1, gicd_reg - GICD_ICACTIVER);
         if ( rank == NULL) goto write_ignore;
         vgic_lock_rank(v, rank);
         rank->iactive &= ~*r;
@@ -577,9 +571,9 @@ struct pending_irq *irq_to_pending(struct vcpu *v, unsigned 
int irq)
 
 void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int irq, int virtual)
 {
-    int idx = irq >> 2, byte = irq & 0x3;
+    int byte = irq & 0x3;
     uint8_t priority;
-    struct vgic_irq_rank *rank = vgic_irq_rank(v, 8, idx);
+    struct vgic_irq_rank *rank = vgic_irq_rank(v, 1, irq / 32);
     struct pending_irq *iter, *n = irq_to_pending(v, irq);
     unsigned long flags;
 
@@ -587,7 +581,7 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int irq, 
int virtual)
     if (!list_empty(&n->inflight))
         return;
 
-    priority = byte_read(rank->ipriority[REG_RANK_INDEX(8, idx)], 0, byte);
+    priority = byte_read(rank->ipriority[REG_RANK_INDEX(8, irq / 4)], 0, byte);
 
     n->irq = irq;
     n->priority = priority;

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