[PATCH v4 17/28] ARM: KVM: Implement HVC_RESET_VECTORS stub hypercall in the init code

Marc Zyngier
2017-03-21T19:20:47Z

In order to restore HYP mode to its original condition, KVM currently
implements __kvm_hyp_reset(). As we're moving towards a hyp-stub
defined API, it becomes necessary to implement HVC_RESET_VECTORS.

This patch adds the HVC_RESET_VECTORS hypercall to the KVM init
code, which so far lacked any form of hypercall support.

Tested-by: Keerthy <j-keerthy@ti.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm/include/asm/virt.h | 1 +
arch/arm/kernel/hyp-stub.S | 2 +-
arch/arm/kvm/init.S | 33 +++++++++++++++++++++++++++------
3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/arch/arm/include/asm/virt.h b/arch/arm/include/asm/virt.h
index 5186718aab68..8d5625b790b5 100644
--- a/arch/arm/include/asm/virt.h
+++ b/arch/arm/include/asm/virt.h
@@ -54,6 +54,7 @@ static inline void sync_boot_mode(void)

void __hyp_set_vectors(unsigned long phys_vector_base);
unsigned long __hyp_get_vectors(void);
+void __hyp_reset_vectors(void);
#else
#define __boot_cpu_mode (SVC_MODE)
#define sync_boot_mode()
diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
index 21794d4a8f36..3cb01e8a291d 100644
--- a/arch/arm/kernel/hyp-stub.S
+++ b/arch/arm/kernel/hyp-stub.S
@@ -280,7 +280,7 @@ ENDPROC(__hyp_reset_vectors)
#endif

.align 5
-__hyp_stub_vectors:
+ENTRY(__hyp_stub_vectors)
__hyp_stub_reset: W(b) .
__hyp_stub_und: W(b) .
__hyp_stub_svc: W(b) .
diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
index bf89c919efc1..9b0c735a68f7 100644
--- a/arch/arm/kvm/init.S
+++ b/arch/arm/kvm/init.S
@@ -23,6 +23,7 @@
#include <asm/kvm_asm.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_mmu.h>
+#include <asm/virt.h>

/********************************************************************
* Hypervisor initialization
@@ -39,6 +40,10 @@
* - Setup the page tables
* - Enable the MMU
* - Profit! (or eret, if you only care about the code).
+ *
+ * Another possibility is to get a HYP stub hypercall.
+ * We discriminate between the two by checking if r0 contains a value
+ * that is less than HVC_STUB_HCALL_NR.
*/

.text
@@ -58,6 +63,10 @@ __kvm_hyp_init:
W(b) .

__do_hyp_init:
+ @ Check for a stub hypercall
+ cmp r0, #HVC_STUB_HCALL_NR
+ blo __kvm_handle_stub_hvc
+
@ Set stack pointer
mov sp, r0

@@ -112,19 +121,31 @@ __do_hyp_init:

eret

- @ r0 : stub vectors address
+ENTRY(__kvm_handle_stub_hvc)
+ cmp r0, #HVC_RESET_VECTORS
+ bne 1f
ENTRY(__kvm_hyp_reset)
/* We're now in idmap, disable MMU */
mrc p15, 4, r1, c1, c0, 0 @ HSCTLR
- ldr r2, =(HSCTLR_M | HSCTLR_A | HSCTLR_C | HSCTLR_I)
- bic r1, r1, r2
+ ldr r0, =(HSCTLR_M | HSCTLR_A | HSCTLR_C | HSCTLR_I)
+ bic r1, r1, r0
mcr p15, 4, r1, c1, c0, 0 @ HSCTLR

- /* Install stub vectors */
- mcr p15, 4, r0, c12, c0, 0 @ HVBAR
- isb
+ /*
+ * Install stub vectors, using ardb's VA->PA trick.
+ */
+0: adr r0, 0b @ PA(0)
+ movw r1, #:lower16:__hyp_stub_vectors - 0b @ VA(stub) - VA(0)
+ movt r1, #:upper16:__hyp_stub_vectors - 0b
+ add r1, r1, r0 @ PA(stub)
+ mcr p15, 4, r1, c12, c0, 0 @ HVBAR
+ b exit
+
+1: mov r0, #-1

+exit:
eret
+ENDPROC(__kvm_handle_stub_hvc)
ENDPROC(__kvm_hyp_reset)

.ltorg
--
2.11.0