xen/arm: vgic-v2: Correctly handle RAZ/WI registers

All the GICv2 registers are word-accessible. Some them are also
byte-accessible (see GICD_IPRIORITYR*).

Those registers are incorrectly implemented when they should be RAZ. Only
word-access size are currently allowed for them.

To avoid further issues, introduce different label following the access-size
of the registers:
    - read_as_zero_32 and write_ignore_32: Used for registers accessible
    via a word.
    - read_as_zero: Used when we don't have to check the access size.

The latter is used when the access size has already been checked in the
register emulation and/or when the register offset is reserved/implementation
defined.

Note that, only used labels has been introduced.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
(cherry picked from commit 1fefa55027)

xen/arch/arm/vgic-v2.c

@@ -72,7 +72,7 @@ static int vgic_v2_distr_mmio_read(struct vcpu *v, mmio_info_t *info)
 
     case GICD_IGROUPR ... GICD_IGROUPRN:
         /* We do not implement security extensions for guests, read zero */
-        goto read_as_zero;
+        goto read_as_zero_32;
 
     case GICD_ISENABLER ... GICD_ISENABLERN:
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -164,7 +164,7 @@ static int vgic_v2_distr_mmio_read(struct vcpu *v, mmio_info_t *info)
 
     case GICD_NSACR ... GICD_NSACRN:
         /* We do not implement security extensions for guests, read zero */
-        goto read_as_zero;
+        goto read_as_zero_32;
 
     case GICD_SGIR:
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -224,8 +224,9 @@ bad_width:
     domain_crash_synchronous();
     return 0;
 
-read_as_zero:
+read_as_zero_32:
     if ( dabt.size != DABT_WORD ) goto bad_width;
+read_as_zero:
     *r = 0;
     return 1;
 }
@@ -285,7 +286,7 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
     /* R/O -- write ignored */
     case GICD_TYPER:
     case GICD_IIDR:
-        goto write_ignore;
+        goto write_ignore_32;
 
     /* Implementation defined -- write ignored */
     case 0x020 ... 0x03c:
@@ -293,7 +294,7 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
 
     case GICD_IGROUPR ... GICD_IGROUPRN:
         /* We do not implement security extensions for guests, write ignore */
-        goto write_ignore;
+        goto write_ignore_32;
 
     case GICD_ISENABLER ... GICD_ISENABLERN:
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -359,7 +360,7 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
 
     case GICD_ITARGETSR ... GICD_ITARGETSR + 7:
         /* SGI/PPI target is read only */
-        goto write_ignore;
+        goto write_ignore_32;
 
     case GICD_ITARGETSR + 8 ... GICD_ITARGETSRN:
     {
@@ -432,10 +433,10 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
         return 1;
 
     case GICD_ICFGR: /* SGIs */
-        goto write_ignore;
+        goto write_ignore_32;
     case GICD_ICFGR + 1: /* PPIs */
         /* It is implementation defined if these are writeable. We chose not */
-        goto write_ignore;
+        goto write_ignore_32;
     case GICD_ICFGR + 2 ... GICD_ICFGRN: /* SPIs */
         if ( dabt.size != DABT_WORD ) goto bad_width;
         rank = vgic_rank_offset(v, 2, gicd_reg - GICD_ICFGR, DABT_WORD);
@@ -447,7 +448,7 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
 
     case GICD_NSACR ... GICD_NSACRN:
         /* We do not implement security extensions for guests, write ignore */
-        goto write_ignore;
+        goto write_ignore_32;
 
     case GICD_SGIR:
         if ( dabt.size != DABT_WORD ) goto bad_width;
@@ -473,7 +474,7 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
 
     /* R/O -- write ignore */
     case GICD_ICPIDR2:
-        goto write_ignore;
+        goto write_ignore_32;
 
     /* Implementation defined -- write ignored */
     case 0xfec ... 0xffc:
@@ -502,8 +503,9 @@ bad_width:
     domain_crash_synchronous();
     return 0;
 
-write_ignore:
+write_ignore_32:
     if ( dabt.size != DABT_WORD ) goto bad_width;
+write_ignore:
     return 1;
 }