[PATCH 2/8] arm64: Convert hcalls to use ISS field

Geoff Levand
2015-01-17T00:23:34Z

To allow for additional hcalls to be defined and to make the arm64 hcall API
more consistent across exception vector routines, change the hcall implementations
to use the ISS field of the ESR_EL2 register to specify the hcall type.

The existing arm64 hcall implementations are limited in that they only allow
for two distinct hcalls; with the x0 register either zero, or not zero. Also,
the API of the hyp-stub exception vector routines and the KVM exception vector
routines differ; hyp-stub uses a non-zero value in x0 to implement
__hyp_set_vectors, whereas KVM uses it to implement kvm_call_hyp.

Define three new preprocessor macros HVC_GET_VECTORS, HVC_SET_VECTORS and
HVC_CALL_HYP and to be used as hcall type specifiers and convert the
existing __hyp_get_vectors(), __hyp_set_vectors() and kvm_call_hyp() routines
to use these new macros when executing an HVC call. Also change the
corresponding hyp-stub and KVM el1_sync exception vector routines to use these
new macros.

Signed-off-by: Geoff Levand <geoff@infradead.org>
---
arch/arm64/include/asm/virt.h | 20 ++++++++++++++++++++
arch/arm64/kernel/hyp-stub.S | 34 ++++++++++++++++++++++------------
arch/arm64/kvm/hyp.S | 18 +++++++++++-------
3 files changed, 53 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 7a5df52..99c319c 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -21,6 +21,26 @@
#define BOOT_CPU_MODE_EL1 (0xe11)
#define BOOT_CPU_MODE_EL2 (0xe12)

+/*
+ * HVC_GET_VECTORS - Return the value of the vbar_el2 register.
+ */
+
+#define HVC_GET_VECTORS 1
+
+/*
+ * HVC_SET_VECTORS - Set the value of the vbar_el2 register.
+ *
+ * @x0: Physical address of the new vector table.
+ */
+
+#define HVC_SET_VECTORS 2
+
+/*
+ * HVC_CALL_HYP - Execute a hyp routine.
+ */
+
+#define HVC_CALL_HYP 3
+
#ifndef __ASSEMBLY__

/*
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index a272f33..e3db3fd 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -22,6 +22,7 @@
#include <linux/irqchip/arm-gic-v3.h>

#include <asm/assembler.h>
+#include <asm/kvm_arm.h>
#include <asm/ptrace.h>
#include <asm/virt.h>

@@ -53,14 +54,22 @@ ENDPROC(__hyp_stub_vectors)
.align 11

el1_sync:
- mrs x1, esr_el2
- lsr x1, x1, #26
- cmp x1, #0x16
- b.ne 2f // Not an HVC trap
- cbz x0, 1f
- msr vbar_el2, x0 // Set vbar_el2
+ mrs x18, esr_el2
+ lsr x17, x18, #ESR_ELx_EC_SHIFT
+ and x18, x18, #ESR_ELx_ISS_MASK
+
+ cmp x17, #ESR_ELx_EC_HVC64
+ b.ne 2f // Not an HVC trap
+
+ cmp x18, #HVC_GET_VECTORS
+ b.ne 1f
+ mrs x0, vbar_el2
b 2f
-1: mrs x0, vbar_el2 // Return vbar_el2
+
+1: cmp x18, #HVC_SET_VECTORS
+ b.ne 2f
+ msr vbar_el2, x0
+
2: eret
ENDPROC(el1_sync)

@@ -100,11 +109,12 @@ ENDPROC(\label)
* initialisation entry point.
*/

-ENTRY(__hyp_get_vectors)
- mov x0, xzr
- // fall through
ENTRY(__hyp_set_vectors)
- hvc #0
+ hvc #HVC_SET_VECTORS
ret
-ENDPROC(__hyp_get_vectors)
ENDPROC(__hyp_set_vectors)
+
+ENTRY(__hyp_get_vectors)
+ hvc #HVC_GET_VECTORS
+ ret
+ENDPROC(__hyp_get_vectors)
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index c0d8202..1916c89 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -27,6 +27,7 @@
#include <asm/kvm_asm.h>
#include <asm/kvm_mmu.h>
#include <asm/memory.h>
+#include <asm/virt.h>

#define CPU_GP_REG_OFFSET(x) (CPU_GP_REGS + x)
#define CPU_XREG_OFFSET(x) CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
@@ -1106,12 +1107,9 @@ __hyp_panic_str:
* in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c). Return values are
* passed in r0 and r1.
*
- * A function pointer with a value of 0 has a special meaning, and is
- * used to implement __hyp_get_vectors in the same way as in
- * arch/arm64/kernel/hyp_stub.S.
*/
ENTRY(kvm_call_hyp)
- hvc #0
+ hvc #HVC_CALL_HYP
ret
ENDPROC(kvm_call_hyp)

@@ -1142,6 +1140,7 @@ el1_sync: // Guest trapped into EL2

mrs x1, esr_el2
lsr x2, x1, #ESR_ELx_EC_SHIFT
+ and x0, x1, #ESR_ELx_ISS_MASK

cmp x2, #ESR_ELx_EC_HVC64
b.ne el1_trap
@@ -1150,15 +1149,19 @@ el1_sync: // Guest trapped into EL2
cbnz x3, el1_trap // called HVC

/* Here, we're pretty sure the host called HVC. */
+ mov x18, x0
pop x2, x3
pop x0, x1

- /* Check for __hyp_get_vectors */
- cbnz x0, 1f
+ cmp x18, #HVC_GET_VECTORS
+ b.ne 1f
mrs x0, vbar_el2
b 2f

-1: push lr, xzr
+1: cmp x18, #HVC_CALL_HYP
+ b.ne 2f
+
+ push lr, xzr

/*
* Compute the function address in EL2, and shuffle the parameters.
@@ -1171,6 +1174,7 @@ el1_sync: // Guest trapped into EL2
blr lr

pop lr, xzr
+
2: eret

el1_trap:
--
2.1.0