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SubjectRe: [PATCH v4 06/12] KVM: arm64: guest debug, add SW break point support
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Will Deacon <will.deacon@arm.com> writes:

> Hi Alex,
>
> On Fri, May 15, 2015 at 03:27:09PM +0100, Alex Bennée wrote:
>> This adds support for SW breakpoints inserted by userspace.
>>
>> We do this by trapping all guest software debug exceptions to the
>> hypervisor (MDCR_EL2.TDE). The exit handler sets an exit reason of
>> KVM_EXIT_DEBUG with the kvm_debug_exit_arch structure holding the
>> exception syndrome information.
>>
>> It will be up to userspace to extract the PC (via GET_ONE_REG) and
>> determine if the debug event was for a breakpoint it inserted. If not
>> userspace will need to re-inject the correct exception restart the
>> hypervisor to deliver the debug exception to the guest.
>>
>> Any other guest software debug exception (e.g. single step or HW
>> assisted breakpoints) will cause an error and the VM to be killed. This
>> is addressed by later patches which add support for the other debug
>> types.
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
>>
>> ---
>> v2
>> - update to use new exit struct
>> - tweak for C setup
>> - do our setup in debug_setup/clear code
>> - fixed up comments
>> v3:
>> - fix spacing in KVM_GUESTDBG_VALID_MASK
>> - fix and clarify wording on kvm_handle_guest_debug
>> - handle error case in kvm_handle_guest_debug
>> - re-word the commit message
>> v4
>> - rm else leg
>> - add r-b-tag
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index ba635c7..33c8143 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>
> Not sure why, but your patches seem to drop the diffstat which makes it
> slightly more onerous for reviewers trying to figure out which bits touch
> their trees. Are you removing it manually?

No - I'm running:

git pps -v 4 origin/master..HEAD -o guestdbg.patches

Where pps is an alias:

pps = format-patch --cover-letter --summary

Manually expanding the alias gives the same results. I'll have a dig to
see what's going on.

>
> Will

--
Alex Bennée


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