[RFC 24/55] KVM: arm64: Forward FP exceptions to the guest hypervisor

Jintack Lim
2017-01-09T06:24:20Z

Forward exceptions due to floating-point register accesses to the guest
hypervisor if it has set CPTR_EL2.TFP bit.

Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
---
arch/arm64/include/asm/kvm_nested.h | 1 +
arch/arm64/kernel/asm-offsets.c | 1 +
arch/arm64/kvm/handle_exit.c | 3 +++
arch/arm64/kvm/handle_exit_nested.c | 6 ++++++
arch/arm64/kvm/hyp/entry.S | 14 ++++++++++++++
arch/arm64/kvm/hyp/hyp-entry.S | 2 +-
6 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 8d36935..54c5ce5 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -3,4 +3,5 @@

int handle_hvc_nested(struct kvm_vcpu *vcpu);
int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe);
+int kvm_handle_fp_asimd(struct kvm_vcpu *vcpu, struct kvm_run *run);
#endif
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 4a2f0f0..b635f1a 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -131,6 +131,7 @@ int main(void)
DEFINE(CPU_FP_REGS, offsetof(struct kvm_regs, fp_regs));
DEFINE(VCPU_FPEXC32_EL2, offsetof(struct kvm_vcpu, arch.ctxt.sys_regs[FPEXC32_EL2]));
DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
+ DEFINE(VIRTUAL_CPTR_EL2, offsetof(struct kvm_vcpu, arch.ctxt.el2_regs[CPTR_EL2]));
#endif
#ifdef CONFIG_CPU_PM
DEFINE(CPU_SUSPEND_SZ, sizeof(struct cpu_suspend_ctx));
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 046fdf8..308f5c5 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -195,6 +195,9 @@ static int kvm_handle_eret(struct kvm_vcpu *vcpu, struct kvm_run *run)
[ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
[ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug,
[ESR_ELx_EC_BRK64] = kvm_handle_guest_debug,
+#ifdef CONFIG_KVM_ARM_NESTED_HYP
+ [ESR_ELx_EC_FP_ASIMD] = kvm_handle_fp_asimd,
+#endif
};

static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/handle_exit_nested.c b/arch/arm64/kvm/handle_exit_nested.c
index 871ecfc..7544c6d 100644
--- a/arch/arm64/kvm/handle_exit_nested.c
+++ b/arch/arm64/kvm/handle_exit_nested.c
@@ -43,3 +43,9 @@ int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe)

return -EINVAL;
}
+
+/* This is only called when virtual CPTR_EL2.TFP bit is set. */
+int kvm_handle_fp_asimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+}
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 12ee62d..a76f102 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -158,6 +158,20 @@ abort_guest_exit_end:
1: ret
ENDPROC(__guest_exit)

+ENTRY(__fpsimd_guest_trap)
+#ifdef CONFIG_KVM_ARM_NESTED_HYP
+// If virtual CPTR_EL2.TFP is set, then foward it to the nested hyp.
+ mrs x1, tpidr_el2
+ ldr x0, [x1, #VIRTUAL_CPTR_EL2]
+ and x0, x0, #CPTR_EL2_TFP
+ cbnz x0, 1f
+#endif
+ b __fpsimd_guest_restore
+1:
+ mov x0, #ARM_EXCEPTION_TRAP
+ b __guest_exit
+ENDPROC(__fpsimd_guest_trap)
+
ENTRY(__fpsimd_guest_restore)
stp x2, x3, [sp, #-16]!
stp x4, lr, [sp, #-16]!
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 4e92399..d83494b 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -108,7 +108,7 @@ el1_trap:

/* Guest accessed VFP/SIMD registers, save host, restore Guest */
cmp x0, #ESR_ELx_EC_FP_ASIMD
- b.eq __fpsimd_guest_restore
+ b.eq __fpsimd_guest_trap

mrs x1, tpidr_el2
mov x0, #ARM_EXCEPTION_TRAP
--
1.9.1