Christoffer Dall <cdall@xxxxxxxxxx> writes:
> On Fri, Oct 06, 2017 at 02:45:35PM +0100, Alex Bennée wrote:
>>
>> Julien Thierry <julien.thierry@xxxxxxx> writes:
>>
>> > On 06/10/17 12:39, Alex Bennée wrote:
>> >> The system state of KVM when using userspace emulation is not complete
>> >> until we return into KVM_RUN. To handle mmio related updates we wait
>> >> until they have been committed and then schedule our KVM_EXIT_DEBUG.
>> >>
>> >> I've introduced a new function kvm_arm_maybe_return_debug() to wrap up
>> >> the differences between arm/arm64 which is currently null for arm.
>> >>
>> >> Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
>> >> ---
>> >> arch/arm/include/asm/kvm_host.h | 2 ++
>> >> arch/arm64/include/asm/kvm_host.h | 1 +
>> >> arch/arm64/kvm/debug.c | 21 +++++++++++++++++++++
>> >> arch/arm64/kvm/handle_exit.c | 9 +++------
>> >> virt/kvm/arm/arm.c | 2 +-
>> >> virt/kvm/arm/mmio.c | 3 ++-
>> >> 6 files changed, 30 insertions(+), 8 deletions(-)
>> >>
>> >> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> >> index 4a879f6ff13b..aec943f6d123 100644
>> >> --- a/arch/arm/include/asm/kvm_host.h
>> >> +++ b/arch/arm/include/asm/kvm_host.h
>> >> @@ -285,6 +285,8 @@ static inline void kvm_arm_init_debug(void) {}
>> >> static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
>> >> static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
>> >> static inline void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) {}
>> >> +static inline int kvm_arm_maybe_return_debug(struct kvm_vcpu *vcpu,
>> >> + struct kvm_run *run) {}
>> >>
>> >
>> > This function should return 1.
>>
>> So I did ponder making this a bool, returning true if we need to exit
>> and testing in v/k/a/arm.c exit leg rather than in the mmio handler.
>>
>> At the moment it mirrors the existing exit logic which follows -1 err, 0
>> return, >0 handled. But as I mentioned in the cover letter this fell
>> down a bit when dealing with the mmio case.
>>
>> >
>> >> int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu,
>> >> struct kvm_device_attr *attr);
>> >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> >> index e923b58606e2..fa67d21662f6 100644
>> >> --- a/arch/arm64/include/asm/kvm_host.h
>> >> +++ b/arch/arm64/include/asm/kvm_host.h
>> >> @@ -369,6 +369,7 @@ void kvm_arm_init_debug(void);
>> >> void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
>> >> void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
>> >> void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
>> >> +int kvm_arm_maybe_return_debug(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> >
>> > I feel the name could be a little bit more explicit:
>> >
>> > kvm_arm_trap_need_step_debug, kvm_arm_trap_step_return_debug,
>> > kvm_arm_trap_need_return_debug.
>>
>> I wanted to keep the debug suffix so that's fine although I'm not so
>> sure trap is correct because on the tail end of mmio emulation are we
>> still trapping?
>>
>> Maybe kvm_arm_step_emulated_debug?
>
> I think you should name it:
>
> kvm_arm_should_complete_emulated_instr_debug() - or something better -
Naming is hard :-/
> and call it directly from kvm_arch_vcpu_ioctl_run, so that it becomes:
>
> ret = kvm_handle_mmio_return(vcpu, vcpu->run);
> if (ret)
> return ret;
> ret = kvm_arm_should_complete_emulated_instr_debug(vcpu);
> if (ret)
> return ret;
This runs into the problem of slightly different ret semantics for here
and in handle_exit. Maybe just having a bool response and:
if (kvm_arm_should_complete_emulated_instr_debug(vcpu))
return 0;
And then in handle_exit:
if (handled == 1 && kvm_arm_should_complete_emulated_instr_debug(vcpu))
return 0;
else
return handled;
?
>
>>
>> > At least, I think it would be nice that the name reflect that this
>> > check is meant for emulated instructions.
>> >
>> > Otherwise:
>> >
>> > Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx>
>> >
>> > Thanks,
>>
>>
> Thanks,
> -Christoffer
--
Alex Bennée
