Subject: [PATCH 11/21] arm64: KVM: Implement the core world switch

From: [email-masked] (Marc Zyngier)
Date: Tue, 24 Nov 2015 17:40:26 +0000

On Tue, 24 Nov 2015 17:29:14 +0000
Alex Benn?e <[email-masked]> wrote:

> 
> Marc Zyngier <[email-masked]> writes:
> 
> > Implement the core of the world switch in C. Not everything is there
> > yet, and there is nothing to re-enter the world switch either.
> >
> > But this already outlines the code structure well enough.
> >
> > Signed-off-by: Marc Zyngier <[email-masked]>
> > ---
> >  arch/arm64/kvm/hyp/Makefile |   1 +
> >  arch/arm64/kvm/hyp/switch.c | 134 ++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 135 insertions(+)
> >  create mode 100644 arch/arm64/kvm/hyp/switch.c
> >
> > diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> > index 1e1ff06..9c11b0f 100644
> > --- a/arch/arm64/kvm/hyp/Makefile
> > +++ b/arch/arm64/kvm/hyp/Makefile
> > @@ -8,3 +8,4 @@ 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
> > +obj-$(CONFIG_KVM_ARM_HOST) += switch.o
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > new file mode 100644
> > index 0000000..a3af81a
> > --- /dev/null
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -0,0 +1,134 @@
> > +/*
> > + * Copyright (C) 2015 - ARM Ltd
> > + * Author: Marc Zyngier <[email-masked]>
> > + *
> > + * 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 "hyp.h"
> > +
> > +static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
> > +{
> > +	u64 val;
> > +
> > +	/*
> > +	 * We are about to set CPTR_EL2.TFP to trap all floating point
> > +	 * register accesses to EL2, however, the ARM ARM clearly states that
> > +	 * traps are only taken to EL2 if the operation would not otherwise
> > +	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
> > +	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
> > +	 */
> > +	val = vcpu->arch.hcr_el2;
> > +	if (val & HCR_RW) {
> > +		write_sysreg(1 << 30, fpexc32_el2);
> > +		isb();
> > +	}
> > +	write_sysreg(val, hcr_el2);
> > +	write_sysreg(1 << 15, hstr_el2);
> > +	write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
> > +	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
> > +}
> > +
> > +static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
> > +{
> > +	write_sysreg(HCR_RW, hcr_el2);
> > +	write_sysreg(0, hstr_el2);
> > +	write_sysreg(read_sysreg(mdcr_el2) & MDCR_EL2_HPMN_MASK, mdcr_el2);
> > +	write_sysreg(0, cptr_el2);
> > +}
> > +
> > +static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
> > +{
> > +	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
> > +	write_sysreg(kvm->arch.vttbr, vttbr_el2);
> > +}
> > +
> > +static void __hyp_text __deactivate_vm(struct kvm_vcpu *vcpu)
> > +{
> > +	write_sysreg(0, vttbr_el2);
> > +}
> > +
> > +static hyp_alternate_select(__vgic_call_save_state,
> > +			    __vgic_v2_save_state, __vgic_v3_save_state,
> > +			    ARM64_HAS_SYSREG_GIC_CPUIF);
> > +
> > +static hyp_alternate_select(__vgic_call_restore_state,
> > +			    __vgic_v2_restore_state, __vgic_v3_restore_state,
> > +			    ARM64_HAS_SYSREG_GIC_CPUIF);
> > +
> > +static void __hyp_text __vgic_save_state(struct kvm_vcpu *vcpu)
> > +{
> > +	__vgic_call_save_state()(vcpu);
> > +	write_sysreg(read_sysreg(hcr_el2) & ~HCR_INT_OVERRIDE, hcr_el2);
> > +}
> > +
> > +static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)
> > +{
> > +	u64 val;
> > +
> > +	val = read_sysreg(hcr_el2);
> > +	val |= 	HCR_INT_OVERRIDE;
> > +	val |= vcpu->arch.irq_lines;
> > +	write_sysreg(val, hcr_el2);
> > +
> > +	__vgic_call_restore_state()(vcpu);
> > +}
> > +
> > +int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
> > +{
> > +	struct kvm_cpu_context *host_ctxt;
> > +	struct kvm_cpu_context *guest_ctxt;
> > +	u64 exit_code;
> > +
> > +	vcpu = kern_hyp_va(vcpu);
> > +	write_sysreg(vcpu, tpidr_el2);
> > +
> > +	host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> > +	guest_ctxt = &vcpu->arch.ctxt;
> > +
> > +	__sysreg_save_state(host_ctxt);
> > +	__debug_cond_save_state(vcpu, &vcpu->arch.host_debug_state, host_ctxt);
> > +
> > +	__activate_traps(vcpu);
> > +	__activate_vm(vcpu);
> > +
> > +	__vgic_restore_state(vcpu);
> > +	__timer_restore_state(vcpu);
> > +
> > +	/*
> > +	 * We must restore the 32-bit state before the sysregs, thanks
> > +	 * to Cortex-A57 erratum #852523.
> > +	 */
> > +	__sysreg32_restore_state(vcpu);
> > +	__sysreg_restore_state(guest_ctxt);
> > +	__debug_restore_state(vcpu, &vcpu->arch.vcpu_debug_state,
> > guest_ctxt);
> 
> Did you right this before guest debug was merged? Now
> vcpu.debug_ptr/VCPU_DEBUG_PTR selects which set of debug registers we
> are going to use before entering the guest.

I probably just overlooked that bit. Thanks for noticing it!

	M.
-- 
Jazz is not dead. It just smells funny.