[PATCH v4 0/5] x86/kvm/hyper-v: add support for synthetic debugger

Jon Doron
2020-03-09T18:20:32Z

Add support for the synthetic debugger interface of hyper-v, the
synthetic debugger has 2 modes.
1. Use a set of MSRs to send/recv information
2. Use hypercalls

The first mode is based the following MSRs:
1. Control/Status MSRs which either asks for a send/recv .
2. Send/Recv MSRs each holds GPA where the send/recv buffers are.
3. Pending MSR, holds a GPA to a PAGE that simply has a boolean that
indicates if there is data pending to issue a recv VMEXIT.

In the first patch the first mode is being implemented in the sense that
it simply exits to user-space when a control MSR is being written and
when the pending MSR is being set, then it's up-to userspace to
implement the rest of the logic of sending/recving.

In the second mode instead of using MSRs KNet will simply issue
Hypercalls with the information to send/recv, in this mode the data
being transferred is UDP encapsulated, unlike in the previous mode in
which you get just the data to send.

The new hypercalls will exit to userspace which will be incharge of
re-encapsulating if needed the UDP packets to be sent.

There is an issue though in which KDNet does not respect the hypercall
page and simply issues vmcall/vmmcall instructions depending on the cpu
type expecting them to be handled as it a real hypercall was issued.

Jon Doron (5):
x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit
x86/hyper-v: Add synthetic debugger definitions
x86/kvm/hyper-v: Add support for synthetic debugger capability
x86/kvm/hyper-v: enable hypercalls regardless of hypercall page
x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

arch/x86/include/asm/hyperv-tlfs.h | 26 +++++
arch/x86/include/asm/kvm_host.h | 13 +++
arch/x86/kvm/hyperv.c | 162 ++++++++++++++++++++++++++++-
arch/x86/kvm/hyperv.h | 5 +
arch/x86/kvm/trace.h | 51 +++++++++
arch/x86/kvm/x86.c | 9 ++
include/uapi/linux/kvm.h | 11 ++
7 files changed, 275 insertions(+), 2 deletions(-)

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2.24.1