On Mon, Dec 11, 2017 at 10:44:59AM +0000, Marc Zyngier wrote:

On 07/12/17 17:06, Christoffer Dall wrote:

quoted

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,

If I may refine the rational: ELR_EL2 and SPSR_EL2 are not useful here
because we never enter a guest as a result of an exception entry that
would be directly handled by KVM. The kernel entry code already saves
ELR_EL1/SPSR_EL1 on exception entry, which is enough.

Indeed, I was being a bit loosey-goosey here.

quoted

factor out these registers into separate save/restore functions, making
it easy to exclude them from the VHE world-switch path later on.

Signed-off-by: Christoffer Dall <redacted>
---
 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 a12112494f75..479de0f0dd07 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c

@@ -71,6 +71,10 @@ 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);
 }

@@ -80,6 +84,7 @@ 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)

@@ -93,6 +98,7 @@ 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)

@@ -137,6 +143,11 @@ 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);
 }

@@ -146,6 +157,7 @@ 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)

@@ -159,6 +171,7 @@ 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)

Otherwise:

Reviewed-by: Marc Zyngier <redacted>

Thanks,
-Christoffer