arm64: KVM: Implement guest entry

Contrary to the previous patch, the guest entry is fairly different
from its assembly counterpart, mostly because it is only concerned
with saving/restoring the GP registers, and nothing else.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

3 files changed, 133 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
index ec14cacc21a6..1e1ff06348cd 100644
--- a/arch/arm64/kvm/hyp/Makefile
+++ b/arch/arm64/kvm/hyp/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_KVM_ARM_HOST) += vgic-v3-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += timer-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += sysreg-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += debug-sr.o
+obj-$(CONFIG_KVM_ARM_HOST) += entry.o
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
new file mode 100644
index 000000000000..ff196951e63b
--- /dev/null
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -0,0 +1,130 @@
+/*
+ * Copyright (C) 2015 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/asm-offsets.h>
+#include <asm/assembler.h>
+#include <asm/fpsimdmacros.h>
+#include <asm/kvm.h>
+#include <asm/kvm_arm.h>
+#include <asm/kvm_asm.h>
+#include <asm/kvm_mmu.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)
+
+        .text
+        .pushsection    .hyp.text, "ax"
+
+.macro save_callee_saved_regs ctxt
+        stp     x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
+        stp     x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
+        stp     x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
+        stp     x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
+        stp     x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
+        stp     x29, lr,  [\ctxt, #CPU_XREG_OFFSET(29)]
+.endm
+
+.macro restore_callee_saved_regs ctxt
+        ldp     x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
+        ldp     x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
+        ldp     x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
+        ldp     x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
+        ldp     x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
+        ldp     x29, lr,  [\ctxt, #CPU_XREG_OFFSET(29)]
+.endm
+
+/*
+ * u64 __guest_enter(struct kvm_vcpu *vcpu,
+ *                   struct kvm_cpu_context *host_ctxt);
+ */
+ENTRY(__guest_enter)
+        // x0: vcpu
+        // x1: host/guest context
+        // x2-x18: clobbered by macros
+
+        // Store the host regs
+        save_callee_saved_regs x1
+
+        // Preserve vcpu & host_ctxt for use at exit time
+        stp     x0, x1, [sp, #-16]!
+
+        add     x1, x0, #VCPU_CONTEXT
+
+        // Prepare x0-x1 for later restore by pushing them onto the stack
+        ldp     x2, x3, [x1, #CPU_XREG_OFFSET(0)]
+        stp     x2, x3, [sp, #-16]!
+
+        // x2-x18
+        ldp     x2, x3,   [x1, #CPU_XREG_OFFSET(2)]
+        ldp     x4, x5,   [x1, #CPU_XREG_OFFSET(4)]
+        ldp     x6, x7,   [x1, #CPU_XREG_OFFSET(6)]
+        ldp     x8, x9,   [x1, #CPU_XREG_OFFSET(8)]
+        ldp     x10, x11, [x1, #CPU_XREG_OFFSET(10)]
+        ldp     x12, x13, [x1, #CPU_XREG_OFFSET(12)]
+        ldp     x14, x15, [x1, #CPU_XREG_OFFSET(14)]
+        ldp     x16, x17, [x1, #CPU_XREG_OFFSET(16)]
+        ldr     x18,      [x1, #CPU_XREG_OFFSET(18)]
+
+        // x19-x29, lr
+        restore_callee_saved_regs x1
+
+        // Last bits of the 64bit state
+        ldp     x0, x1, [sp], #16
+
+        // Do not touch any register after this!
+        eret
+ENDPROC(__guest_enter)
+
+ENTRY(__guest_exit)
+        // x0: vcpu
+        // x1: return code
+        // x2-x3: free
+        // x4-x29,lr: vcpu regs
+        // vcpu x0-x3 on the stack
+
+        add     x2, x0, #VCPU_CONTEXT
+
+        stp     x4, x5,   [x2, #CPU_XREG_OFFSET(4)]
+        stp     x6, x7,   [x2, #CPU_XREG_OFFSET(6)]
+        stp     x8, x9,   [x2, #CPU_XREG_OFFSET(8)]
+        stp     x10, x11, [x2, #CPU_XREG_OFFSET(10)]
+        stp     x12, x13, [x2, #CPU_XREG_OFFSET(12)]
+        stp     x14, x15, [x2, #CPU_XREG_OFFSET(14)]
+        stp     x16, x17, [x2, #CPU_XREG_OFFSET(16)]
+        str     x18,      [x2, #CPU_XREG_OFFSET(18)]
+
+        ldp     x6, x7, [sp], #16       // x2, x3
+        ldp     x4, x5, [sp], #16       // x0, x1
+
+        stp     x4, x5, [x2, #CPU_XREG_OFFSET(0)]
+        stp     x6, x7, [x2, #CPU_XREG_OFFSET(2)]
+
+        save_callee_saved_regs x2
+
+        // Restore vcpu & host_ctxt from the stack
+        // (preserving return code in x1)
+        ldp     x0, x2, [sp], #16
+        // Now restore the host regs
+        restore_callee_saved_regs x2
+
+        mov     x0, x1
+        ret
+ENDPROC(__guest_exit)
+
+        /* Insert fault handling here */
diff --git a/arch/arm64/kvm/hyp/hyp.h b/arch/arm64/kvm/hyp/hyp.h
index 454e46f9c15e..080965348def 100644
--- a/arch/arm64/kvm/hyp/hyp.h
+++ b/arch/arm64/kvm/hyp/hyp.h
@@ -52,5 +52,7 @@ void __debug_restore_state(struct kvm_vcpu *vcpu,
 void __debug_cond_save_host_state(struct kvm_vcpu *vcpu);
 void __debug_cond_restore_host_state(struct kvm_vcpu *vcpu);
 
+u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt);
+
 #endif /* __ARM64_KVM_HYP_H__ */