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

Tue Feb 9 10:44:55 PST 2016

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 at 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 at 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 at linaro.org>