[PATCH v4 04/28] arm64: hyp-stub: Implement HVC_RESET_VECTORS stub hypercall

Marc Zyngier
2017-03-21T19:20:34Z

Let's define a new stub hypercall that resets the HYP configuration
to its default: hyp-stub vectors, and MMU disabled.

Of course, for the hyp-stub itself, this is a trivial no-op.
Hypervisors will have a bit more work to do.

Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/include/asm/virt.h | 9 +++++++++
arch/arm64/kernel/hyp-stub.S | 11 ++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 439f6b5d31f6..f24f1eb72dc0 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -39,6 +39,14 @@
*/
#define HVC_SOFT_RESTART 2

+/*
+ * HVC_RESET_VECTORS - Restore the vectors to the original HYP stubs
+ */
+#define HVC_RESET_VECTORS 3
+
+/* Max number of HYP stub hypercalls */
+#define HVC_STUB_HCALL_NR 4
+
#define BOOT_CPU_MODE_EL1 (0xe11)
#define BOOT_CPU_MODE_EL2 (0xe12)

@@ -62,6 +70,7 @@ extern u32 __boot_cpu_mode[2];

void __hyp_set_vectors(phys_addr_t phys_vector_base);
phys_addr_t __hyp_get_vectors(void);
+void __hyp_reset_vectors(void);

/* Reports the availability of HYP mode */
static inline bool is_hyp_mode_available(void)
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index 193dfb25ce2f..dd0a7522fbe1 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -73,8 +73,11 @@ el1_sync:
mov x1, x3
br x4 // no return

+3: cmp x0, #HVC_RESET_VECTORS
+ beq 9f // Nothing to reset!
+
/* Someone called kvm_call_hyp() against the hyp-stub... */
-3: mov x0, #ARM_EXCEPTION_HYP_GONE
+ mov x0, #ARM_EXCEPTION_HYP_GONE

9: eret
ENDPROC(el1_sync)
@@ -127,3 +130,9 @@ ENTRY(__hyp_set_vectors)
hvc #0
ret
ENDPROC(__hyp_set_vectors)
+
+ENTRY(__hyp_reset_vectors)
+ mov x0, #HVC_RESET_VECTORS
+ hvc #0
+ ret
+ENDPROC(__hyp_reset_vectors)
--
2.11.0