[PATCH] xen/arm: Warn user on cpu errata 832075

[Bertrand Marquis <bertrand.marquis@arm.com>]

When a Cortex A57 processor is affected by CPU errata 832075, a guest
not implementing the workaround for it could deadlock the system.
Add a warning during boot informing the user that only trusted guests
should be executed on the system.
An equivalent warning is already given to the user by KVM on cores
affected by this errata.

Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
---
 xen/arch/arm/cpuerrata.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
index 6c09017515..8f9ab6dde1 100644
--- a/xen/arch/arm/cpuerrata.c
+++ b/xen/arch/arm/cpuerrata.c
@@ -240,6 +240,26 @@ static int enable_ic_inv_hardening(void *data)
 
 #endif
 
+#ifdef CONFIG_ARM64_ERRATUM_832075
+
+static int warn_device_load_acquire_errata(void *data)
+{
+    static bool warned = false;
+
+    if ( !warned )
+    {
+        warning_add("This CPU is affected by the errata 832075.\n"
+                    "Guests without required CPU erratum workarounds\n"
+                    "can deadlock the system!\n"
+                    "Only trusted guests should be used on this system.\n");
+        warned = true;
+    }
+
+    return 0;
+}
+
+#endif
+
 #ifdef CONFIG_ARM_SSBD
 
 enum ssbd_state ssbd_state = ARM_SSBD_RUNTIME;
@@ -419,6 +439,7 @@ static const struct arm_cpu_capabilities arm_errata[] = {
         .capability = ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE,
         MIDR_RANGE(MIDR_CORTEX_A57, 0x00,
                    (1 << MIDR_VARIANT_SHIFT) | 2),
+        .enable = warn_device_load_acquire_errata,
     },
 #endif
 #ifdef CONFIG_ARM64_ERRATUM_834220
-- 
2.17.1