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

[Bandan Das <bsd@redhat.com>]

Hi Jintack,

Jintack Lim <jintack.lim@linaro.org> writes:

> 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.

Do you mean that compilation will fail ? It seems these functions are
defined separately in 32/64 bit specific header files. Or is it that
64 bit compilation also depends on the 32 bit header file ?

Bandan

> 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
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