[Xen-devel] [RFC 13/16] xen/arm: arm64: Add Cortex-A53 cache errata workaround

[Julien Grall <julien.grall@xxxxxxx>]

The ARM errata 819472, 827319 and 824069 define the same workaround for
these hardware issues in certain Cortex-A53 parts.

The cache instructions "dc cvac" and "dc cvau" need to be upgraded to
"dc civac".

Use the alternative framework to replace those instructions only on
affected cores.

Whilst the errata affect cache instructions issued at any exception
level, it is not necessary to trap EL1/EL0 data cache instructions
access in order to upgrade them. Indeed the data cache corruption would
always be at the address used by the data cache instructions. Note that
this address could point to a shared memory between guests and the
hypervisors, however all the information present in it are be validated
before any use.

Therefore a malicious guest could only hurt itself. Note that all the
guests should implement/enable the workaround for the affected cores.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
 docs/misc/arm/silicon-errata.txt |  3 ++
 xen/arch/arm/Kconfig             | 71 ++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/arm64/cache.S       |  8 ++++-
 xen/arch/arm/cpuerrata.c         | 17 ++++++++++
 xen/include/asm-arm/arm64/page.h |  7 +++-
 xen/include/asm-arm/cpufeature.h |  4 ++-
 xen/include/asm-arm/processor.h  |  6 ++++
 7 files changed, 113 insertions(+), 3 deletions(-)

diff --git a/docs/misc/arm/silicon-errata.txt b/docs/misc/arm/silicon-errata.txt
index 3f0d32b..9a2983b 100644
--- a/docs/misc/arm/silicon-errata.txt
+++ b/docs/misc/arm/silicon-errata.txt
@@ -42,4 +42,7 @@ stable hypervisors.
 | Implementor    | Component       | Erratum ID      | Kconfig                 
|
 
+----------------+-----------------+-----------------+-------------------------+
 | ARM            | Cortex-A15      | #766422         | N/A                     
|
+| ARM            | Cortex-A53      | #827319         | ARM64_ERRATUM_827319    
|
+| ARM            | Cortex-A53      | #824069         | ARM64_ERRATUM_824069    
|
+| ARM            | Cortex-A53      | #819472         | ARM64_ERRATUM_819472    
|
 | ARM            | Cortex-A57      | #852523         | N/A                     
|
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index 9b3e66b..6e4c769 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -53,6 +53,77 @@ config ALTERNATIVE
 
 endmenu
 
+menu "ARM errata workaround via the alternative framework"
+       depends on ALTERNATIVE
+
+config ARM64_ERRATUM_827319
+       bool "Cortex-A53: 827319: Data cache clean instructions might cause 
overlapping transactions to the interconnect"
+       default y
+       depends on ARM_64
+       help
+         This option adds an alternative code sequence to work around ARM
+         erratum 827319 on Cortex-A53 parts up to r0p2 with an AMBA 5 CHI
+         master interface and an L2 cache.
+
+         Under certain conditions this erratum can cause a clean line eviction
+         to occur at the same time as another transaction to the same address
+         on the AMBA 5 CHI interface, which can cause data corruption if the
+         interconnect reorders the two transactions.
+
+         The workaround promotes data cache clean instructions to
+         data cache clean-and-invalidate.
+         Please note that this does not necessarily enable the workaround,
+         as it depends on the alternative framework, which will only patch
+         the kernel if an affected CPU is detected.
+
+         If unsure, say Y.
+
+config ARM64_ERRATUM_824069
+       bool "Cortex-A53: 824069: Cache line might not be marked as clean after 
a CleanShared snoop"
+       default y
+       depends on ARM_64
+       help
+         This option adds an alternative code sequence to work around ARM
+         erratum 824069 on Cortex-A53 parts up to r0p2 when it is connected
+         to a coherent interconnect.
+
+         If a Cortex-A53 processor is executing a store or prefetch for
+         write instruction at the same time as a processor in another
+         cluster is executing a cache maintenance operation to the same
+         address, then this erratum might cause a clean cache line to be
+         incorrectly marked as dirty.
+
+         The workaround promotes data cache clean instructions to
+         data cache clean-and-invalidate.
+         Please note that this option does not necessarily enable the
+         workaround, as it depends on the alternative framework, which will
+         only patch the kernel if an affected CPU is detected.
+
+         If unsure, say Y.
+
+config ARM64_ERRATUM_819472
+       bool "Cortex-A53: 819472: Store exclusive instructions might cause data 
corruption"
+       default y
+       depends on ARM_64
+       help
+         This option adds an alternative code sequence to work around ARM
+         erratum 819472 on Cortex-A53 parts up to r0p1 with an L2 cache
+         present when it is connected to a coherent interconnect.
+
+         If the processor is executing a load and store exclusive sequence at
+         the same time as a processor in another cluster is executing a cache
+         maintenance operation to the same address, then this erratum might
+         cause data corruption.
+
+         The workaround promotes data cache clean instructions to
+         data cache clean-and-invalidate.
+         Please note that this does not necessarily enable the workaround,
+         as it depends on the alternative framework, which will only patch
+         the kernel if an affected CPU is detected.
+
+         If unsure, say Y.
+endmenu
+
 source "common/Kconfig"
 
 source "drivers/Kconfig"
diff --git a/xen/arch/arm/arm64/cache.S b/xen/arch/arm/arm64/cache.S
index bc5a8f7..1a0c80c 100644
--- a/xen/arch/arm/arm64/cache.S
+++ b/xen/arch/arm/arm64/cache.S
@@ -19,6 +19,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <asm/alternative.h>
+
 /*
  * dcache_line_size - get the minimum D-cache line size from the CTR register.
  */
@@ -54,7 +56,11 @@ ENTRY(flush_icache_range)
        sub     x3, x2, #1
        bic     x4, x0, x3
 1:
-       dc      cvau, x4                // clean D line to PoU
+alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE
+       dc      cvau, x4
+alternative_else
+       dc      civac, x4
+alternative_endif
        add     x4, x4, x2
        cmp     x4, x1
        b.lo    1b
diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
index 52d39f8..211b520 100644
--- a/xen/arch/arm/cpuerrata.c
+++ b/xen/arch/arm/cpuerrata.c
@@ -17,6 +17,23 @@ is_affected_midr_range(const struct arm_cpu_capabilities 
*entry)
 }
 
 static const struct arm_cpu_capabilities arm_errata[] = {
+#if defined(CONFIG_ARM64_ERRATUM_827319) || \
+    defined(CONFIG_ARM64_ERRATUM_824069)
+    {
+        /* Cortex-A53 r0p[012] */
+        .desc = "ARM errata 827319, 824069",
+        .capability = ARM64_WORKAROUND_CLEAN_CACHE,
+        MIDR_RANGE(MIDR_CORTEX_A53, 0x00, 0x02),
+    },
+#endif
+#ifdef CONFIG_ARM64_ERRATUM_819472
+    {
+        /* Cortex-A53 r0[01] */
+        .desc = "ARM erratum 819472",
+        .capability = ARM64_WORKAROUND_CLEAN_CACHE,
+        MIDR_RANGE(MIDR_CORTEX_A53, 0x00, 0x01),
+    },
+#endif
     {},
 };
 
diff --git a/xen/include/asm-arm/arm64/page.h b/xen/include/asm-arm/arm64/page.h
index fbdc8fb..79ef7bd 100644
--- a/xen/include/asm-arm/arm64/page.h
+++ b/xen/include/asm-arm/arm64/page.h
@@ -3,6 +3,8 @@
 
 #ifndef __ASSEMBLY__
 
+#include <asm/alternative.h>
+
 /* Write a pagetable entry */
 static inline void write_pte(lpae_t *p, lpae_t pte)
 {
@@ -18,7 +20,10 @@ static inline void write_pte(lpae_t *p, lpae_t pte)
 #define __invalidate_dcache_one(R) "dc ivac, %" #R ";"
 
 /* Inline ASM to flush dcache on register R (may be an inline asm operand) */
-#define __clean_dcache_one(R) "dc cvac, %" #R ";"
+#define __clean_dcache_one(R)                   \
+    ALTERNATIVE("dc cvac, %" #R ";",            \
+                "dc civac, %" #R ";",           \
+                ARM64_WORKAROUND_CLEAN_CACHE)   \
 
 /* Inline ASM to clean and invalidate dcache on register R (may be an
  * inline asm operand) */
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index fb57295..474a778 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -35,7 +35,9 @@
 #endif
 #define cpu_has_security  (boot_cpu_feature32(security) > 0)
 
-#define ARM_NCAPS           0
+#define ARM64_WORKAROUND_CLEAN_CACHE    0
+
+#define ARM_NCAPS           1
 
 #ifndef __ASSEMBLY__
 
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 1b701c5..4123951 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -44,6 +44,12 @@
         _model == (model) && _rv >= (rv_min) && _rv <= (rv_max);        \
 })
 
+#define ARM_CPU_IMP_ARM             0x41
+
+#define ARM_CPU_PART_CORTEX_A53     0xD03
+
+#define MIDR_CORTEX_A53 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, 
ARM_CPU_PART_CORTEX_A53)
+
 /* MPIDR Multiprocessor Affinity Register */
 #define _MPIDR_UP           (30)
 #define MPIDR_UP            (_AC(1,U) << _MPIDR_UP)
-- 
1.9.1


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