[PATCH 21/37] KVM: arm64: Don't save the host ELR_EL2 and SPSR_EL2 on VHE systems

[Christoffer Dall]

On non-VHE systems we need to save the ELR_EL2 and SPSR_EL2 so that we
can return to the host in EL1 in the same state and location where we
issued a hypercall to EL2, but these registers don't contain anything
important on VHE, because all of the host runs in EL2.  Therefore,
exclude them when saving/restoring the host state.

Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
---
 arch/arm64/kvm/hyp/sysreg-sr.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index f5c1b44..354ca02 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -66,6 +66,10 @@ static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt->gp_regs.sp_el1		= read_sysreg(sp_el1);
 	ctxt->gp_regs.elr_el1		= read_sysreg_el1(elr);
 	ctxt->gp_regs.spsr[KVM_SPSR_EL1]= read_sysreg_el1(spsr);
+}
+
+static void __hyp_text __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt)
+{
 	ctxt->gp_regs.regs.pc		= read_sysreg_el2(elr);
 	ctxt->gp_regs.regs.pstate	= read_sysreg_el2(spsr);
 }
@@ -75,6 +79,7 @@ void __hyp_text __sysreg_save_state_nvhe(struct kvm_cpu_context *ctxt)
 	__sysreg_save_el1_state(ctxt);
 	__sysreg_save_common_state(ctxt);
 	__sysreg_save_user_state(ctxt);
+	__sysreg_save_el2_return_state(ctxt);
 }
 
 void sysreg_save_host_state_vhe(struct kvm_cpu_context *ctxt)
@@ -88,6 +93,7 @@ void sysreg_save_guest_state_vhe(struct kvm_cpu_context *ctxt)
 	__sysreg_save_el1_state(ctxt);
 	__sysreg_save_common_state(ctxt);
 	__sysreg_save_user_state(ctxt);
+	__sysreg_save_el2_return_state(ctxt);
 }
 
 static void __hyp_text __sysreg_restore_common_state(struct kvm_cpu_context *ctxt)
@@ -127,6 +133,11 @@ static void __hyp_text __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
 	write_sysreg(ctxt->gp_regs.sp_el1,		sp_el1);
 	write_sysreg_el1(ctxt->gp_regs.elr_el1,		elr);
 	write_sysreg_el1(ctxt->gp_regs.spsr[KVM_SPSR_EL1],spsr);
+}
+
+static void __hyp_text
+__sysreg_restore_el2_return_state(struct kvm_cpu_context *ctxt)
+{
 	write_sysreg_el2(ctxt->gp_regs.regs.pc,		elr);
 	write_sysreg_el2(ctxt->gp_regs.regs.pstate,	spsr);
 }
@@ -136,6 +147,7 @@ void __hyp_text __sysreg_restore_state_nvhe(struct kvm_cpu_context *ctxt)
 	__sysreg_restore_el1_state(ctxt);
 	__sysreg_restore_common_state(ctxt);
 	__sysreg_restore_user_state(ctxt);
+	__sysreg_restore_el2_return_state(ctxt);
 }
 
 void sysreg_restore_host_state_vhe(struct kvm_cpu_context *ctxt)
@@ -149,6 +161,7 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
 	__sysreg_restore_el1_state(ctxt);
 	__sysreg_restore_common_state(ctxt);
 	__sysreg_restore_user_state(ctxt);
+	__sysreg_restore_el2_return_state(ctxt);
 }
 
 static void __hyp_text __fpsimd32_save_state(struct kvm_cpu_context *ctxt)
-- 
2.9.0