Re: [RFC 11/55] KVM: arm64: Emulate taking an exception to the guest hypervisor

[Christoffer Dall <cdall@linaro.org>]

On Mon, Jan 09, 2017 at 01:24:07AM -0500, Jintack Lim wrote:
> Emulate taking an exception to the guest hypervisor running in the
> virtual EL2 as described in ARM ARM AArch64.TakeException().

I would rename the subject and change the description of this patch to
talk about injecting exceptions to virtual EL2 as opposed to talking
about the guest hypervisor.

> 
> Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
> ---
>  arch/arm/include/asm/kvm_emulate.h   | 14 ++++++++
>  arch/arm64/include/asm/kvm_emulate.h | 19 +++++++++++
>  arch/arm64/kvm/Makefile              |  2 ++
>  arch/arm64/kvm/emulate-nested.c      | 66 ++++++++++++++++++++++++++++++++++++
>  arch/arm64/kvm/trace.h               | 20 +++++++++++
>  5 files changed, 121 insertions(+)
>  create mode 100644 arch/arm64/kvm/emulate-nested.c
> 
> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> index 0a03b7d..0fa2f5a 100644
> --- a/arch/arm/include/asm/kvm_emulate.h
> +++ b/arch/arm/include/asm/kvm_emulate.h
> @@ -47,6 +47,20 @@ static inline void vcpu_set_reg(struct kvm_vcpu *vcpu, u8 reg_num,
>  void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
>  void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
>  
> +static inline int kvm_inject_nested_sync(struct kvm_vcpu *vcpu, u64 esr_el2)
> +{
> +	kvm_err("Unexpected call to %s for the non-nesting configuration\n",
> +		 __func__);
> +	return -EINVAL;
> +}
> +
> +static inline int kvm_inject_nested_irq(struct kvm_vcpu *vcpu)
> +{
> +	kvm_err("Unexpected call to %s for the non-nesting configuration\n",
> +		 __func__);
> +	return -EINVAL;
> +}
> +
>  static inline void kvm_arm_setup_shadow_state(struct kvm_vcpu *vcpu) { };
>  static inline void kvm_arm_restore_shadow_state(struct kvm_vcpu *vcpu) { };
>  static inline void kvm_arm_init_cpu_context(kvm_cpu_context_t *cpu_ctxt) { };
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 8892c82..0987ee4 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -42,6 +42,25 @@
>  void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
>  void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
>  
> +#ifdef CONFIG_KVM_ARM_NESTED_HYP
> +int kvm_inject_nested_sync(struct kvm_vcpu *vcpu, u64 esr_el2);
> +int kvm_inject_nested_irq(struct kvm_vcpu *vcpu);
> +#else
> +static inline int kvm_inject_nested_sync(struct kvm_vcpu *vcpu, u64 esr_el2)
> +{
> +	kvm_err("Unexpected call to %s for the non-nesting configuration\n",
> +		 __func__);
> +	return -EINVAL;
> +}
> +
> +static inline int kvm_inject_nested_irq(struct kvm_vcpu *vcpu)
> +{
> +	kvm_err("Unexpected call to %s for the non-nesting configuration\n",
> +		 __func__);
> +	return -EINVAL;
> +}
> +#endif
> +
>  void kvm_arm_setup_shadow_state(struct kvm_vcpu *vcpu);
>  void kvm_arm_restore_shadow_state(struct kvm_vcpu *vcpu);
>  void kvm_arm_init_cpu_context(kvm_cpu_context_t *cpu_ctxt);
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 7811d27..b342bdd 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -34,3 +34,5 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-its.o
>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/irqchip.o
>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o
>  kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o
> +
> +kvm-$(CONFIG_KVM_ARM_NESTED_HYP) += emulate-nested.o
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> new file mode 100644
> index 0000000..59d147f
> --- /dev/null
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -0,0 +1,66 @@
> +/*
> + * Copyright (C) 2016 - Columbia University
> + * Author: Jintack Lim <jintack@cs.columbia.edu>
> + *
> + * 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 <linux/kvm.h>
> +#include <linux/kvm_host.h>
> +
> +#include <asm/kvm_emulate.h>
> +
> +#include "trace.h"
> +
> +#define	EL2_EXCEPT_SYNC_OFFSET	0x400
> +#define	EL2_EXCEPT_ASYNC_OFFSET	0x480

I don't like the 'EXCEPT' word here.  Don't we have other defines in the
kernel with more appropriate naming schemes we can rely on?

> +
> +
> +/*
> + *  Emulate taking an exception. See ARM ARM J8.1.2 AArch64.TakeException()
> + */
> +static int kvm_inject_nested(struct kvm_vcpu *vcpu, u64 esr_el2,
> +			     int exception_offset)
> +{
> +	int ret = 1;
> +	kvm_cpu_context_t *ctxt = &vcpu->arch.ctxt;
> +
> +	/* We don't inject an exception recursively to virtual EL2 */
> +	if (vcpu_mode_el2(vcpu))
> +		BUG();

Why not?

> +
> +	ctxt->el2_regs[SPSR_EL2] = *vcpu_cpsr(vcpu);
> +	ctxt->el2_regs[ELR_EL2] = *vcpu_pc(vcpu);
> +	ctxt->el2_regs[ESR_EL2] = esr_el2;
> +
> +	/* On an exception, PSTATE.SP = 1 */

You can probably loose this comment.

> +	*vcpu_cpsr(vcpu) = PSR_MODE_EL2h;
> +	*vcpu_cpsr(vcpu) |=  (PSR_A_BIT | PSR_F_BIT | PSR_I_BIT | PSR_D_BIT);
> +	*vcpu_pc(vcpu) = ctxt->el2_regs[VBAR_EL2] + exception_offset;
> +
> +	trace_kvm_inject_nested_exception(vcpu, esr_el2, *vcpu_pc(vcpu));
> +
> +	return ret;
> +}
> +
> +int kvm_inject_nested_sync(struct kvm_vcpu *vcpu, u64 esr_el2)
> +{
> +	return kvm_inject_nested(vcpu, esr_el2, EL2_EXCEPT_SYNC_OFFSET);
> +}
> +
> +int kvm_inject_nested_irq(struct kvm_vcpu *vcpu)
> +{
> +	u64 esr_el2 = kvm_vcpu_get_hsr(vcpu);
> +	/* We supports only IRQ and FIQ, so the esr_el2 is not updated. */

I don't understand this comment.

I think you need some whitespace here before the comment and explain a
little more context about why we can reuse the ESR register on the vcpu
struct here.

Also 's/supports/support/'

> +	return kvm_inject_nested(vcpu, esr_el2, EL2_EXCEPT_ASYNC_OFFSET);
> +}
> diff --git a/arch/arm64/kvm/trace.h b/arch/arm64/kvm/trace.h
> index 7fb0008..7c86cfb 100644
> --- a/arch/arm64/kvm/trace.h
> +++ b/arch/arm64/kvm/trace.h
> @@ -167,6 +167,26 @@
>  );
>  
>  
> +TRACE_EVENT(kvm_inject_nested_exception,
> +	TP_PROTO(struct kvm_vcpu *vcpu, unsigned long esr_el2,
> +		 unsigned long pc),
> +	TP_ARGS(vcpu, esr_el2, pc),
> +
> +	TP_STRUCT__entry(
> +		__field(struct kvm_vcpu *,	vcpu)
> +		__field(unsigned long,		esr_el2)
> +		__field(unsigned long,		pc)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->vcpu = vcpu;
> +		__entry->esr_el2 = esr_el2;
> +		__entry->pc = pc;
> +	),
> +
> +	TP_printk("vcpu: %p, inject exception to vEL2: ESR_EL2 0x%lx, vector: 0x%016lx",
> +		  __entry->vcpu, __entry->esr_el2, __entry->pc)
> +);
>  #endif /* _TRACE_ARM64_KVM_H */
>  
>  #undef TRACE_INCLUDE_PATH
> -- 
> 1.9.1
> 
>