[PATCH v2 16/28] ARM: KVM: Add the new world switch implementation

Christoffer Dall
2016-02-09T18:44:55Z

On Thu, Feb 04, 2016 at 11:00:33AM +0000, Marc Zyngier wrote:
> The new world switch implementation is modeled after the arm64 one,
> calling the various save/restore functions in turn, and having as
> little state as possible.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm/kvm/hyp/Makefile | 1 +
> arch/arm/kvm/hyp/hyp.h | 7 +++
> arch/arm/kvm/hyp/switch.c | 136 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 144 insertions(+)
> create mode 100644 arch/arm/kvm/hyp/switch.c
>
> diff --git a/arch/arm/kvm/hyp/Makefile b/arch/arm/kvm/hyp/Makefile
> index c779690..cfab402 100644
> --- a/arch/arm/kvm/hyp/Makefile
> +++ b/arch/arm/kvm/hyp/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_KVM_ARM_HOST) += vgic-v2-sr.o
> obj-$(CONFIG_KVM_ARM_HOST) += vfp.o
> obj-$(CONFIG_KVM_ARM_HOST) += banked-sr.o
> obj-$(CONFIG_KVM_ARM_HOST) += entry.o
> +obj-$(CONFIG_KVM_ARM_HOST) += switch.o
> diff --git a/arch/arm/kvm/hyp/hyp.h b/arch/arm/kvm/hyp/hyp.h
> index b3f6ed2..2ca651f 100644
> --- a/arch/arm/kvm/hyp/hyp.h
> +++ b/arch/arm/kvm/hyp/hyp.h
> @@ -60,11 +60,16 @@
> #define CNTV_CVAL __ACCESS_CP15_64(3, c14)
> #define CNTVOFF __ACCESS_CP15_64(4, c14)
>
> +#define MIDR __ACCESS_CP15(c0, 0, c0, 0)
> #define CSSELR __ACCESS_CP15(c0, 2, c0, 0)
> +#define VMIDR __ACCESS_CP15(c0, 4, c0, 0)

Nit: This is called VPIDR in v7 and VMPIDR_EL2 in v8 IIUC. Should we
refer to it by one of those names instead?

> #define VMPIDR __ACCESS_CP15(c0, 4, c0, 5)
> #define SCTLR __ACCESS_CP15(c1, 0, c0, 0)
> #define CPACR __ACCESS_CP15(c1, 0, c0, 2)
> +#define HCR __ACCESS_CP15(c1, 4, c1, 0)
> +#define HDCR __ACCESS_CP15(c1, 4, c1, 1)
> #define HCPTR __ACCESS_CP15(c1, 4, c1, 2)
> +#define HSTR __ACCESS_CP15(c1, 4, c1, 3)
> #define TTBCR __ACCESS_CP15(c2, 0, c0, 2)
> #define DACR __ACCESS_CP15(c3, 0, c0, 0)
> #define DFSR __ACCESS_CP15(c5, 0, c0, 0)
> @@ -73,6 +78,7 @@
> #define AIFSR __ACCESS_CP15(c5, 0, c1, 1)
> #define DFAR __ACCESS_CP15(c6, 0, c0, 0)
> #define IFAR __ACCESS_CP15(c6, 0, c0, 2)
> +#define HDFAR __ACCESS_CP15(c6, 4, c0, 0)
> #define ICIALLUIS __ACCESS_CP15(c7, 0, c1, 0)
> #define TLBIALLIS __ACCESS_CP15(c8, 0, c3, 0)
> #define TLBIALLNSNHIS __ACCESS_CP15(c8, 4, c3, 4)
> @@ -85,6 +91,7 @@
> #define TID_URW __ACCESS_CP15(c13, 0, c0, 2)
> #define TID_URO __ACCESS_CP15(c13, 0, c0, 3)
> #define TID_PRIV __ACCESS_CP15(c13, 0, c0, 4)
> +#define HTPIDR __ACCESS_CP15(c13, 4, c0, 2)
> #define CNTKCTL __ACCESS_CP15(c14, 0, c1, 0)
> #define CNTV_CTL __ACCESS_CP15(c14, 0, c3, 1)
> #define CNTHCTL __ACCESS_CP15(c14, 4, c1, 0)
> diff --git a/arch/arm/kvm/hyp/switch.c b/arch/arm/kvm/hyp/switch.c
> new file mode 100644
> index 0000000..f715b0d
> --- /dev/null
> +++ b/arch/arm/kvm/hyp/switch.c
> @@ -0,0 +1,136 @@
> +/*
> + * Copyright (C) 2015 - ARM Ltd
> + * Author: Marc Zyngier <marc.zyngier@arm.com>
> + *
> + * 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 <asm/kvm_asm.h>
> +#include "hyp.h"
> +
> +__asm__(".arch_extension virt");
> +
> +static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu, u32 *fpexc)

Nit: can you document the fpexc or name it host_fpexc_preserve or something?

> +{
> + u32 val;
> +
> + /*
> + * We are about to set HCPTR.TCP10/11 to trap all floating point
> + * register accesses to HYP, however, the ARM ARM clearly states that
> + * traps are only taken to HYP if the operation would not otherwise
> + * trap to SVC. Therefore, always make sure that for 32-bit guests,
> + * we set FPEXC.EN to prevent traps to SVC, when setting the TCP bits.
> + */
> + val = read_sysreg(VFP_FPEXC);
> + *fpexc = val;
> + if (!(val & FPEXC_EN)) {
> + write_sysreg(val | FPEXC_EN, VFP_FPEXC);
> + isb();
> + }
> +
> + write_sysreg(vcpu->arch.hcr | vcpu->arch.irq_lines, HCR);
> + /* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
> + write_sysreg(HSTR_T(15), HSTR);
> + write_sysreg(HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11), HCPTR);
> + val = read_sysreg(HDCR);
> + write_sysreg(val | HDCR_TPM | HDCR_TPMCR, HDCR);
> +}
> +
> +static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
> +{
> + u32 val;
> +
> + write_sysreg(0, HCR);
> + write_sysreg(0, HSTR);
> + val = read_sysreg(HDCR);
> + write_sysreg(val & ~(HDCR_TPM | HDCR_TPMCR), HDCR);
> + write_sysreg(0, HCPTR);
> +}
> +
> +static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
> +{
> + struct kvm *kvm = kern_hyp_va(vcpu->kvm);
> + write_sysreg(kvm->arch.vttbr, VTTBR);
> + write_sysreg(vcpu->arch.midr, VMIDR);
> +}
> +
> +static void __hyp_text __deactivate_vm(struct kvm_vcpu *vcpu)
> +{
> + write_sysreg(0, VTTBR);
> + write_sysreg(read_sysreg(MIDR), VMIDR);
> +}
> +
> +static void __hyp_text __vgic_save_state(struct kvm_vcpu *vcpu)
> +{
> + __vgic_v2_save_state(vcpu);
> +}
> +
> +static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)
> +{
> + __vgic_v2_restore_state(vcpu);
> +}
> +
> +static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_cpu_context *host_ctxt;
> + struct kvm_cpu_context *guest_ctxt;
> + bool fp_enabled;
> + u64 exit_code;
> + u32 fpexc;
> +
> + vcpu = kern_hyp_va(vcpu);
> + write_sysreg(vcpu, HTPIDR);
> +
> + host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> + guest_ctxt = &vcpu->arch.ctxt;
> +
> + __sysreg_save_state(host_ctxt);
> + __banked_save_state(host_ctxt);
> +
> + __activate_traps(vcpu, &fpexc);
> + __activate_vm(vcpu);
> +
> + __vgic_restore_state(vcpu);
> + __timer_restore_state(vcpu);
> +
> + __sysreg_restore_state(guest_ctxt);
> + __banked_restore_state(guest_ctxt);
> +
> + /* Jump in the fire! */
> + exit_code = __guest_enter(vcpu, host_ctxt);
> + /* And we're baaack! */
> +
> + fp_enabled = __vfp_enabled();
> +
> + __banked_save_state(guest_ctxt);
> + __sysreg_save_state(guest_ctxt);
> + __timer_save_state(vcpu);
> + __vgic_save_state(vcpu);
> +
> + __deactivate_traps(vcpu);
> + __deactivate_vm(vcpu);
> +
> + __banked_restore_state(host_ctxt);
> + __sysreg_restore_state(host_ctxt);
> +
> + if (fp_enabled) {
> + __vfp_save_state(&guest_ctxt->vfp);
> + __vfp_restore_state(&host_ctxt->vfp);
> + }
> +
> + write_sysreg(fpexc, VFP_FPEXC);
> +
> + return exit_code;
> +}
> +
> +__alias(__guest_run) int __weak __kvm_vcpu_run(struct kvm_vcpu *vcpu);
> --
> 2.1.4
>

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>