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[Xen-devel] [PATCH MM-PART1 v3 1/8] xen/arm: Don't boot Xen on platform using AIVIVT instruction caches

The AIVIVT is a type of instruction cache available on Armv7. This is
the only cache not implementing the IVIPT extension and therefore
requiring specific care.

To simplify maintenance requirements, Xen will not boot on platform
using AIVIVT cache.

This should not be an issue because Xen Arm32 can only boot on a small
number of processors (see arch/arm/arm32/proc-v7.S). All of them are
not using AIVIVT cache.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>


    Changes in v3:
        - Patch added
 xen/arch/arm/setup.c            | 5 +++++
 xen/include/asm-arm/processor.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index ccb0f181ea..faaf029b99 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -526,10 +526,15 @@ static void __init setup_mm(unsigned long dtb_paddr, 
size_t dtb_size)
     unsigned long boot_mfn_start, boot_mfn_end;
     int i;
     void *fdt;
+    const uint32_t ctr = READ_CP32(CTR);
     if ( !bootinfo.mem.nr_banks )
         panic("No memory bank\n");
+    /* We only supports instruction caches implementing the IVIPT extension. */
+    if ( ((ctr >> CTR_L1Ip_SHIFT) & CTR_L1Ip_MASK) == CTR_L1Ip_AIVIVT )
+        panic("AIVIVT instruction cache not supported\n");
     ram_start = bootinfo.mem.bank[0].start;
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index b5f515805d..04b05b3f39 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -6,6 +6,11 @@
 #include <public/arch-arm.h>
+/* CTR Cache Type Register */
+#define CTR_L1Ip_MASK       0x3
+#define CTR_L1Ip_SHIFT      14
+#define CTR_L1Ip_AIVIVT     0x1
 /* MIDR Main ID Register */
 #define MIDR_REVISION_MASK      0xf
 #define MIDR_RESIVION(midr)     ((midr) & MIDR_REVISION_MASK)

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