Re: [PATCH v4 03/12] KVM: arm64: guest debug, define API headers

["Alex Bennée" <alex.bennee@linaro.org>]

Mark Rutland <mark.rutland@arm.com> writes:

> On Fri, May 15, 2015 at 03:27:06PM +0100, Alex Bennée wrote:
>> This commit defines the API headers for guest debugging. There are two
>> architecture specific debug structures:
>> 
>>   - kvm_guest_debug_arch, allows us to pass in HW debug registers
>>   - kvm_debug_exit_arch, signals exception and possible faulting address
>> 
>> The type of debugging being used is controlled by the architecture
>> specific control bits of the kvm_guest_debug->control flags in the ioctl
>> structure.
>> 
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
>> Reviewed-by: Andrew Jones <drjones@redhat.com>
>> Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
>> 
>> ---
>> v2
>>    - expose hsr and pc directly to user-space
>> v3
>>    - s/control/controlled/ in commit message
>>    - add v8 to ARM ARM comment (ARM Architecture Reference Manual)
>>    - add rb tag
>>    - rm pc, add far
>>    - re-word comments on alignment
>>    - rename KVM_ARM_NDBG_REGS -> KVM_ARM_MAX_DBG_REGS
>> v4
>>    - now uses common HW/SW BP define
>>    - add a-b-tag
>>    - use u32 for control regs
>> 
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index d268320..8796610 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -100,10 +100,28 @@ struct kvm_sregs {
>>  struct kvm_fpu {
>>  };
>>  
>> +/*
>> + * See v8 ARM ARM D7.3: Debug Registers
>> + *
>> + * The control registers are architecturally defined as 32 bits but are
>> + * stored as 64 bit values alongside the value registers. This is done
>
> Stale comment? They're stored as __u32 below.

Gah yes it is. 

> It's possible that the registers could grow in future as happened in the
> case of CLIDR_EL1, so it might be worth treating system registers
> generally as u64 values.

Really? I mean the existing debug *control* registers have reserved bits
24-31 so there is space for expansion. 

>
> Mark.
>
>> + * to keep the copying of these values into the vcpu context simple as
>> + * everything is 64 bit aligned (see DBGBCR0_EL1 onwards in kvm_asm.h).
>> + *
>> + * The architectural limit is 16 debug registers of each type although
>> + * in practice there are usually less (see ID_AA64DFR0_EL1).
>> + */
>> +#define KVM_ARM_MAX_DBG_REGS 16
>>  struct kvm_guest_debug_arch {
>> +	__u32 dbg_bcr[KVM_ARM_MAX_DBG_REGS];
>> +	__u64 dbg_bvr[KVM_ARM_MAX_DBG_REGS];
>> +	__u32 dbg_wcr[KVM_ARM_MAX_DBG_REGS];
>> +	__u64 dbg_wvr[KVM_ARM_MAX_DBG_REGS];
>>  };
>>  
>>  struct kvm_debug_exit_arch {
>> +	__u32 hsr;
>> +	__u64 far;
>>  };
>>  
>>  struct kvm_sync_regs {
>> -- 
>> 2.3.5
>> 
>> _______________________________________________
>> kvmarm mailing list
>> kvmarm@lists.cs.columbia.edu
>> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

-- 
Alex Bennée