On 07/30/2012 02:37 AM, Bhushan Bharat-R65777 wrote:
>
>
>> -----Original Message-----
>> From: Wood Scott-B07421
>> Sent: Friday, July 27, 2012 7:00 AM
>> To: Bhushan Bharat-R65777
>> Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; agraf@xxxxxxx; Bhushan Bharat-
>> R65777
>> Subject: Re: [PATCH 2/2] KVM: PPC: booke/bookehv: Add guest debug support
>>
>> On 07/26/2012 12:32 AM, Bharat Bhushan wrote:
>>> This patch adds:
>>> 1) KVM debug handler added for e500v2.
>>> 2) Guest debug by qemu gdb stub.
>>
>> Does it make sense for these to both be in the same patch? If there's common
>> code used by both, that could be added first.
>
> ok
>
>>
>>> Signed-off-by: Liu Yu <yu.liu@xxxxxxxxxxxxx>
>>> Signed-off-by: Varun Sethi <Varun.Sethi@xxxxxxxxxxxxx>
>>> [bharat.bhushan@xxxxxxxxxxxxx: Substantial changes]
>>> Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
>>> ---
>>> arch/powerpc/include/asm/kvm.h | 21 +++++
>>> arch/powerpc/include/asm/kvm_host.h | 7 ++
>>> arch/powerpc/include/asm/kvm_ppc.h | 2 +
>>> arch/powerpc/include/asm/reg_booke.h | 1 +
>>> arch/powerpc/kernel/asm-offsets.c | 31 ++++++-
>>> arch/powerpc/kvm/booke.c | 146 +++++++++++++++++++++++++++---
>>> arch/powerpc/kvm/booke_interrupts.S | 160
>> ++++++++++++++++++++++++++++++++-
>>> arch/powerpc/kvm/bookehv_interrupts.S | 141 ++++++++++++++++++++++++++++-
>>> arch/powerpc/kvm/e500mc.c | 3 +-
>>> arch/powerpc/kvm/powerpc.c | 2 +-
>>> 10 files changed, 492 insertions(+), 22 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/kvm.h
>>> b/arch/powerpc/include/asm/kvm.h index 3c14202..da71c84 100644
>>> --- a/arch/powerpc/include/asm/kvm.h
>>> +++ b/arch/powerpc/include/asm/kvm.h
>>> @@ -25,6 +25,7 @@
>>> /* Select powerpc specific features in <linux/kvm.h> */ #define
>>> __KVM_HAVE_SPAPR_TCE #define __KVM_HAVE_PPC_SMT
>>> +#define __KVM_HAVE_GUEST_DEBUG
>>>
>>> struct kvm_regs {
>>> __u64 pc;
>>> @@ -265,10 +266,19 @@ struct kvm_fpu { };
>>>
>>> struct kvm_debug_exit_arch {
>>> + __u32 exception;
>>> + __u32 pc;
>>> + __u32 status;
>>> };
>>
>> PC must be 64-bit. What goes in "status" and "exception"?
>
> ok
>
>>
>>> /* for KVM_SET_GUEST_DEBUG */
>>> struct kvm_guest_debug_arch {
>>> + struct {
>>> + __u64 addr;
>>> + __u32 type;
>>> + __u32 pad1;
>>> + __u64 pad2;
>>> + } bp[16];
>>> };
>>
>> What goes in "type"?
>
> Type denote breakpoint, read watchpoint, write watchpoint or watchpoint (both read and write). Will adding a comment to describe this is ok?
Yes, please make sure all of this is well documented.
>>> /* definition of registers in kvm_run */ @@ -285,6 +295,17 @@ struct
>>> kvm_sync_regs {
>>> #define KVM_CPU_3S_64 4
>>> #define KVM_CPU_E500MC 5
>>>
>>> +/* Debug related defines */
>>> +#define KVM_INST_GUESTGDB 0x7C00021C /* ehpriv OC=0 */
>>
>> Will this work on all PPC?
>>
>> It certainly won't work on other architectures, so at a minimum it's
>> KVM_PPC_INST_GUEST_GDB, but maybe it needs to be determined at runtime.
>
> How to determine at run time? adding another ioctl ?
Or extend an existing one. Is there any other information about debug
capabilities that you expose -- number of hardware breakpoints
supported, etc?
>>> +#define KVM_GUESTDBG_USE_SW_BP 0x00010000
>>> +#define KVM_GUESTDBG_USE_HW_BP 0x00020000
>>
>> Where do these get used? Any reason for these particular values? If you're
>> trying to create a partition where the upper half is generic and the lower half
>> is arch-specific, say so.
>
> KVM_SET_GUEST_DEBUG ioctl used to set/unset debug interrupts, which
> have a "u32 control" element. We have inherited this mechanism from
> x86 implementation and it looks like lower 16 bits are generic (like
> KVM_GUESTDBG_ENBLE, KVM_GUESTDBG_SINGLESTEP etc and upper 16 bits are
> Architecture specific.
>
> I will add a comment to describe this.
I don't think the sw/hw distinction belongs here -- it should be per
breakpoint.
>>> + run->exit_reason = KVM_EXIT_DEBUG;
>>> + run->debug.arch.pc = vcpu->arch.pc;
>>> + run->debug.arch.exception = exit_nr;
>>> + run->debug.arch.status = 0;
>>> + kvmppc_account_exit(vcpu, DEBUG_EXITS);
>>> + return RESUME_HOST;
>>
>> The interface isn't (clearly labelled as) booke specific, but you return booke-
>> specific exception numbers. How's userspace supposed to know what to do with
>> them? What do you plan on doing with them in QEMU?
>
> This is booke specific.
Then put booke in the name, but what about it really needs to be booke
specific? Why does QEMU care about the exception type?
>>> +#ifndef CONFIG_PPC_FSL_BOOK3E
>>> + PPC_LD(r7, VCPU_HOST_DBG+KVMPPC_DBG_IAC3, r4)
>>> + PPC_LD(r8, VCPU_HOST_DBG+KVMPPC_DBG_IAC4, r4)
>>> + mtspr SPRN_IAC3, r7
>>> + mtspr SPRN_IAC4, r8
>>> +#endif
>>
>> Can you handle this at runtime with a feature section?
>
> Why you want this to make run time? Removing config_ ?
Currently KVM hardcodes the target hardware in a way that is
unacceptable in much of the rest of the kernel. We have a long term
goal to stop doing that, and we should avoid making it worse by adding
random ifdefs for specific CPUs.
-Scott
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