> -----Original Message-----
> From: Alexander Graf [mailto:ag...@suse.de]
> Sent: Friday, February 01, 2013 1:36 PM
> To: Bhushan Bharat-R65777
> Cc: kvm-...@vger.kernel.org; kvm@vger.kernel.org
> Subject: Re: [PATCH 3/8] KVM: PPC: booke: Added debug handler
>
>
> On 01.02.2013, at 06:04, Bhushan Bharat-R65777 wrote:
>
> >
> >
> >> -----Original Message-----
> >> From: kvm-ppc-ow...@vger.kernel.org
> >> [mailto:kvm-ppc-ow...@vger.kernel.org] On Behalf Of Alexander Graf
> >> Sent: Thursday, January 31, 2013 10:38 PM
> >> To: Bhushan Bharat-R65777
> >> Cc: kvm-...@vger.kernel.org; kvm@vger.kernel.org
> >> Subject: Re: [PATCH 3/8] KVM: PPC: booke: Added debug handler
> >>
> >>
> >> On 31.01.2013, at 17:58, Bhushan Bharat-R65777 wrote:
> >>
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Alexander Graf [mailto:ag...@suse.de]
> >>>> Sent: Thursday, January 31, 2013 5:47 PM
> >>>> To: Bhushan Bharat-R65777
> >>>> Cc: kvm-...@vger.kernel.org; kvm@vger.kernel.org
> >>>> Subject: Re: [PATCH 3/8] KVM: PPC: booke: Added debug handler
> >>>>
> >>>>
> >>>> On 30.01.2013, at 12:30, Bhushan Bharat-R65777 wrote:
> >>>>
> >>>>>
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Alexander Graf [mailto:ag...@suse.de]
> >>>>>> Sent: Friday, January 25, 2013 5:13 PM
> >>>>>> To: Bhushan Bharat-R65777
> >>>>>> Cc: kvm-...@vger.kernel.org; kvm@vger.kernel.org; Bhushan
> >>>>>> Bharat-R65777
> >>>>>> Subject: Re: [PATCH 3/8] KVM: PPC: booke: Added debug handler
> >>>>>>
> >>>>>>
> >>>>>> On 16.01.2013, at 09:24, Bharat Bhushan wrote:
> >>>>>>
> >>>>>>> From: Bharat Bhushan <bharat.bhus...@freescale.com>
> >>>>>>>
> >>>>>>> Installed debug handler will be used for guest debug support and
> >>>>>>> debug facility emulation features (patches for these features
> >>>>>>> will follow this patch).
> >>>>>>>
> >>>>>>> Signed-off-by: Liu Yu <yu....@freescale.com>
> >>>>>>> [bharat.bhus...@freescale.com: Substantial changes]
> >>>>>>> Signed-off-by: Bharat Bhushan <bharat.bhus...@freescale.com>
> >>>>>>> ---
> >>>>>>> arch/powerpc/include/asm/kvm_host.h | 1 +
> >>>>>>> arch/powerpc/kernel/asm-offsets.c | 1 +
> >>>>>>> arch/powerpc/kvm/booke_interrupts.S | 49
> ++++++++++++++++++++++++++++++-
> >> --
> >>>> --
> >>>>>>> 3 files changed, 44 insertions(+), 7 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/arch/powerpc/include/asm/kvm_host.h
> >>>>>>> b/arch/powerpc/include/asm/kvm_host.h
> >>>>>>> index 8a72d59..f4ba881 100644
> >>>>>>> --- a/arch/powerpc/include/asm/kvm_host.h
> >>>>>>> +++ b/arch/powerpc/include/asm/kvm_host.h
> >>>>>>> @@ -503,6 +503,7 @@ struct kvm_vcpu_arch {
> >>>>>>> u32 tlbcfg[4];
> >>>>>>> u32 mmucfg;
> >>>>>>> u32 epr;
> >>>>>>> + u32 crit_save;
> >>>>>>> struct kvmppc_booke_debug_reg dbg_reg; #endif
> >>>>>>> gpa_t paddr_accessed;
> >>>>>>> diff --git a/arch/powerpc/kernel/asm-offsets.c
> >>>>>>> b/arch/powerpc/kernel/asm-offsets.c
> >>>>>>> index 46f6afd..02048f3 100644
> >>>>>>> --- a/arch/powerpc/kernel/asm-offsets.c
> >>>>>>> +++ b/arch/powerpc/kernel/asm-offsets.c
> >>>>>>> @@ -562,6 +562,7 @@ int main(void)
> >>>>>>> DEFINE(VCPU_LAST_INST, offsetof(struct kvm_vcpu,
> >>>>>>> arch.last_inst));
> >>>>>>> DEFINE(VCPU_FAULT_DEAR, offsetof(struct kvm_vcpu,
> arch.fault_dear));
> >>>>>>> DEFINE(VCPU_FAULT_ESR, offsetof(struct kvm_vcpu,
> >>>>>>> arch.fault_esr));
> >>>>>>> + DEFINE(VCPU_CRIT_SAVE, offsetof(struct kvm_vcpu,
> >>>>>>> +arch.crit_save));
> >>>>>>> #endif /* CONFIG_PPC_BOOK3S */
> >>>>>>> #endif /* CONFIG_KVM */
> >>>>>>>
> >>>>>>> diff --git a/arch/powerpc/kvm/booke_interrupts.S
> >>>>>>> b/arch/powerpc/kvm/booke_interrupts.S
> >>>>>>> index eae8483..dd9c5d4 100644
> >>>>>>> --- a/arch/powerpc/kvm/booke_interrupts.S
> >>>>>>> +++ b/arch/powerpc/kvm/booke_interrupts.S
> >>>>>>> @@ -52,12 +52,7 @@
> >>>>>>> (1<<BOOKE_INTERRUPT_PROGRAM) | \
> >>>>>>> (1<<BOOKE_INTERRUPT_DTLB_MISS))
> >>>>>>>
> >>>>>>> -.macro KVM_HANDLER ivor_nr scratch srr0
> >>>>>>> -_GLOBAL(kvmppc_handler_\ivor_nr)
> >>>>>>> - /* Get pointer to vcpu and record exit number. */
> >>>>>>> - mtspr \scratch , r4
> >>>>>>> - mfspr r4, SPRN_SPRG_THREAD
> >>>>>>> - lwz r4, THREAD_KVM_VCPU(r4)
> >>>>>>> +.macro __KVM_HANDLER ivor_nr scratch srr0
> >>>>>>> stw r3, VCPU_GPR(R3)(r4)
> >>>>>>> stw r5, VCPU_GPR(R5)(r4)
> >>>>>>> stw r6, VCPU_GPR(R6)(r4)
> >>>>>>> @@ -74,6 +69,46 @@ _GLOBAL(kvmppc_handler_\ivor_nr)
> >>>>>>> bctr
> >>>>>>> .endm
> >>>>>>>
> >>>>>>> +.macro KVM_HANDLER ivor_nr scratch srr0
> >>>>>>> +_GLOBAL(kvmppc_handler_\ivor_nr)
> >>>>>>> + /* Get pointer to vcpu and record exit number. */
> >>>>>>> + mtspr \scratch , r4
> >>>>>>> + mfspr r4, SPRN_SPRG_THREAD
> >>>>>>> + lwz r4, THREAD_KVM_VCPU(r4)
> >>>>>>> + __KVM_HANDLER \ivor_nr \scratch \srr0 .endm
> >>>>>>> +
> >>>>>>> +.macro KVM_DBG_HANDLER ivor_nr scratch srr0
> >>>>>>> +_GLOBAL(kvmppc_handler_\ivor_nr)
> >>>>>>> + mtspr \scratch, r4
> >>>>>>> + mfspr r4, SPRN_SPRG_THREAD
> >>>>>>> + lwz r4, THREAD_KVM_VCPU(r4)
> >>>>>>> + stw r3, VCPU_CRIT_SAVE(r4)
> >>>>>>> + mfcr r3
> >>>>>>> + mfspr r4, SPRN_CSRR1
> >>>>>>> + andi. r4, r4, MSR_PR
> >>>>>>> + bne 1f
> >>>>>>
> >>>>>>
> >>>>>>> + /* debug interrupt happened in enter/exit path */
> >>>>>>> + mfspr r4, SPRN_CSRR1
> >>>>>>> + rlwinm r4, r4, 0, ~MSR_DE
> >>>>>>> + mtspr SPRN_CSRR1, r4
> >>>>>>> + lis r4, 0xffff
> >>>>>>> + ori r4, r4, 0xffff
> >>>>>>> + mtspr SPRN_DBSR, r4
> >>>>>>> + mfspr r4, SPRN_SPRG_THREAD
> >>>>>>> + lwz r4, THREAD_KVM_VCPU(r4)
> >>>>>>> + mtcr r3
> >>>>>>> + lwz r3, VCPU_CRIT_SAVE(r4)
> >>>>>>> + mfspr r4, \scratch
> >>>>>>> + rfci
> >>>>>>
> >>>>>> What is this part doing? Try to ignore the debug exit?
> >>>>>
> >>>>> As BOOKE doesn't have hardware support for virtualization,
> >>>>> hardware never know
> >>>> current pc is in guest or in host.
> >>>>> So when enable hardware single step for guest, it cannot be
> >>>>> disabled at the
> >>>> time guest exit. Thus, we'll see that an single step interrupt
> >>>> happens at the beginning of guest exit path.
> >>>>>
> >>>>> With the above code we recognize this kind of single step
> >>>>> interrupt disable
> >>>> single step and rfci.
> >>>>>
> >>>>>> Why would we have MSR_DE
> >>>>>> enabled in the first place when we can't handle it?
> >>>>>
> >>>>> When QEMU is using hardware debug resource then we always set
> >>>>> MSR_DE during
> >>>> guest is running.
> >>>>
> >>>> Right, but why is MSR_DE enabled during the exit path? If MSR_DE
> >>>> wasn't set, you wouldn't get a single step exit.
> >>>
> >>> We always set MSR_DE in hw MSR when qemu using the debug resource.
> >>
> >> In the _guest_ MSR, yes. But once we exit the guest, it shouldn't be
> >> set anymore, because we're in an interrupt handler, no? Or is MSR_DE
> >> kept alive on interrupts?
> >>
> >>>
> >>>> During the exit code path, you could then swap DBSR back to what
> >>>> the host expects (which means no single step). Only after that
> >>>> enable MSR_DE again.
> >>>
> >>> We do not support deferred debug interrupt, so we do save restore dbsr.
> >>>
> >>>>
> >>>>>
> >>>>>>
> >>>>>>> +1: /* debug interrupt happened in guest */
> >>>>>>> + mtcr r3
> >>>>>>> + mfspr r4, SPRN_SPRG_THREAD
> >>>>>>> + lwz r4, THREAD_KVM_VCPU(r4)
> >>>>>>> + lwz r3, VCPU_CRIT_SAVE(r4)
> >>>>>>> + __KVM_HANDLER \ivor_nr \scratch \srr0
> >>>>>>
> >>>>>> I don't think you need the __KVM_HANDLER split. This should be
> >>>>>> quite easily refactorable into a simple DBG prolog.
> >>>>>
> >>>>> Can you please elaborate how you are envisioning this?
> >>>>
> >>>> With this patch, you have
> >>>>
> >>>> KVM_HANLDER:
> >>>>
> >>>> <code>
> >>>> __KVM_HANDLER
> >>>>
> >>>> KVM_DBG_HANDLER:
> >>>>
> >>>> <code>
> >>>> __KVM_HANDLER
> >>>>
> >>>> Right?
> >>>>
> >>>> In KVM_HANDLER, you get:
> >>>>
> >>>>> .macro KVM_HANDLER ivor_nr scratch srr0
> >>>>> _GLOBAL(kvmppc_handler_\ivor_nr)
> >>>>> /* Get pointer to vcpu and record exit number. */
> >>>>> mtspr \scratch , r4
> >>>>> mfspr r4, SPRN_SPRG_THREAD
> >>>>> lwz r4, THREAD_KVM_VCPU(r4)
> >>>>> __KVM_HANDLER \ivor_nr \scratch \srr0 .endm
> >>>>
> >>>>
> >>>> while KVM_DBG_HANDLER is:
> >>>>
> >>>>> +.macro KVM_DBG_HANDLER ivor_nr scratch srr0
> >>>>> +_GLOBAL(kvmppc_handler_\ivor_nr)
> >>>>> <debug specific handling>
> >>>>> +1: /* debug interrupt happened in guest */
> >>>>> + mtcr r3
> >>>>> + mfspr r4, SPRN_SPRG_THREAD
> >>>>> + lwz r4, THREAD_KVM_VCPU(r4)
> >>>>> + lwz r3, VCPU_CRIT_SAVE(r4)
> >>>>> + __KVM_HANDLER \ivor_nr \scratch \srr0 .endm
> >>>>
> >>>>
> >>>> So if you write this as
> >>>>
> >>>> KVM_DBG_HANDLER:
> >>>> <debug specific handling>
> >>>> 1:
> >>>> mtcr r3
> >>>> mfspr r4, SPRN_SPRG_THREAD
> >>>> lwz r4, THREAD_KVM_VCPU(r4)
> >>>> lwz r3, VCPU_CRIT_SAVE(r4)
> >>>> lwz r4, \scratch
> >>>> <KVM_HANDLER>
> >>>>
> >>>> then you get code that is slower :) but it should be easier to
> >>>> read, since the interface between the individual pieces is always the
> >>>> same.
> >>>> Debug shouldn't be a fast path anyway, right?
> >>>
> >>> Frankly speaking I do not see much difference :).
> >>>
> >>> If we have to do as you mentioned then I think we can just do
> >>>
> >>> KVM_DBG_HANDLER:
> >>> <debug specific handling>
> >>> 1:
> >>> mtcr r3
> >>> lwz r3, VCPU_CRIT_SAVE(r4)
> >>> lwz r4, \scratch
> >>> <KVM_HANDLER>
> >>
> >> Whatever it takes to keep the oddball (debug) an oddball and keep the
> >> normal case easy :).
> >
> > I think there will be another problem as the kvmppc_handler_\ivor_nr will
> > not
> be the starting address which is required as per our ivor/ivpr usages for
> booke
> architecture.
> >
> > I am thinking of keeping as is :).
>
> How about we take a hybrid approach? You write the code as I described above,
> but call __KVM_HANDLER at the end. The normal KVM_HANDLER would look like:
>
> KVM_HANDLER:
> kvmppc_handler_\ivor_nr:
> __KVM_HANDLER ...
>
> That way the code should still be more understandable :)
>
With my current Patch it is defined as:
.macro KVM_HANDLER ivor_nr scratch srr0
_GLOBAL(kvmppc_handler_\ivor_nr)
/* Get pointer to vcpu and record exit number. */
mtspr \scratch , r4
mfspr r4, SPRN_SPRG_THREAD
lwz r4, THREAD_KVM_VCPU(r4)
__KVM_HANDLER \ivor_nr \scratch \srr0
.endm
.macro KVM_DBG_HANDLER ivor_nr scratch srr0
_GLOBAL(kvmppc_handler_\ivor_nr)
<<<<<<Debug related handling>>>>>
1: /* debug interrupt happened in guest */
mtcr r3
mfspr r4, SPRN_SPRG_THREAD
lwz r4, THREAD_KVM_VCPU(r4)
lwz r3, VCPU_CRIT_SAVE(r4)
__KVM_HANDLER \ivor_nr \scratch \srr0
.endm
So the kvmppc_handler_\ivor_nr is defined and should always be at the start of
exception handling?
So if KVM_DBG_HANDLER need to call KVM_HANDLER then there will be issue of 2
definition for DBG interrupt.
I am sorry but I did not understood how you want this to define. Can you please
describe ?
Thanks
-Bharat
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