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

Jintack Lim
2017-06-06T20:38:56Z

Hi Bandan,

On Tue, Jun 6, 2017 at 4:21 PM, Bandan Das <bsd@redhat.com> wrote:
> Jintack Lim <jintack@cs.columbia.edu> writes:
>
>> Emulate taking an exception to the guest hypervisor running in the
>> virtual EL2 as described in ARM ARM AArch64.TakeException().
>
> ARM newbie here, I keep thinking of ARM ARM as a typo ;)

ARM ARM means ARM Architecture Reference Manual :)

> ...
>> +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;
>> +}
>> +
>
> I see these function stubs for aarch32 in the patches. I don't see how they
> can actually be called though. Is this because eventually, there will be
> a virtual el2 mode for aarch32 ?

Current RFC doesn't support nested virtualization on 32bit arm
architecture and those functions will be never called. Those functions
are there for the compilation.

Thanks,
Jintack

>
> Bandan
>
>> 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
>> +
>> +
>> +/*
>> + * 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();
>> +
>> + 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 */
>> + *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. */
>> + 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
> _______________________________________________
> kvmarm mailing list
> kvmarm at lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm