On Wed, Nov 08, 2017 at 06:03:23PM +0100, Andrew Jones wrote:
> On Thu, Oct 12, 2017 at 12:41:25PM +0200, Christoffer Dall wrote:
> > 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.
>
> This commit message implies we start excluding now, but this patch
> actually has no functional change. It just prepares things for
> patch 27/37 "KVM: arm64: Defer saving/restoring system registers to
> vcpu load/put on VHE". Can you please clarify it?
>
Sure:
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,
factor out these registers into separate save/restore functions, making
it easy to exclude them from the VHE world-switch path later on.
Thanks,
-Christoffer
>
> >
> > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> > ---
> > 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
> >
