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KVM: document KVM_SET_GUEST_DEBUG api

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In preparation for working on the ARM implementation I noticed the debug
interface was missing from the API document. I've pieced together the
expected behaviour from the code and commit messages written it up as
best I can.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Alex Bennée 2014-09-09 17:27:18 +01:00 • committed by Paolo Bonzini
parent f2a2516088
commit 4bd9d3441e
1 changed files with 44 additions and 0 deletions
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44
Documentation/virtual/kvm/api.txt
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@ -2565,6 +2565,50 @@ associated with the service will be forgotten, and subsequent RTAS
calls by the guest for that service will be passed to userspace to be calls by the guest for that service will be passed to userspace to be
handled. handled.
4.87 KVM_SET_GUEST_DEBUG
Capability: KVM_CAP_SET_GUEST_DEBUG
Architectures: x86, s390, ppc
Type: vcpu ioctl
Parameters: struct kvm_guest_debug (in)
Returns: 0 on success; -1 on error
struct kvm_guest_debug {
__u32 control;
__u32 pad;
struct kvm_guest_debug_arch arch;
};
Set up the processor specific debug registers and configure vcpu for
handling guest debug events. There are two parts to the structure, the
first a control bitfield indicates the type of debug events to handle
when running. Common control bits are:
- KVM_GUESTDBG_ENABLE: guest debugging is enabled
- KVM_GUESTDBG_SINGLESTEP: the next run should single-step
The top 16 bits of the control field are architecture specific control
flags which can include the following:
- KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86]
- KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390]
- KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
- KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
For example KVM_GUESTDBG_USE_SW_BP indicates that software breakpoints
are enabled in memory so we need to ensure breakpoint exceptions are
correctly trapped and the KVM run loop exits at the breakpoint and not
running off into the normal guest vector. For KVM_GUESTDBG_USE_HW_BP
we need to ensure the guest vCPUs architecture specific registers are
updated to the correct (supplied) values.
The second part of the structure is architecture specific and
typically contains a set of debug registers.
When debug events exit the main run loop with the reason
KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
structure containing architecture specific debug information.
5. The kvm_run structure 5. The kvm_run structure
------------------------ ------------------------