[PATCH v2 4/4] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

Jon Doron
2020-03-05T14:01:47Z

There is another mode for the synthetic debugger which uses hypercalls
to send/recv network data instead of the MSR interface.

This interface is much slower and less recommended since you might get
a lot of VMExits while KDVM polling for new packets to recv, rather
than simply checking the pending page to see if there is data avialble
and then request.

Signed-off-by: Jon Doron <arilou@gmail.com>
---
arch/x86/include/asm/hyperv-tlfs.h | 5 +++++
arch/x86/kvm/hyperv.c | 17 +++++++++++++++++
2 files changed, 22 insertions(+)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 8efdf974c23f..4fa6bf3732a6 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -283,6 +283,8 @@
#define HV_X64_MSR_SYNDBG_PENDING_BUFFER 0x400000F5
#define HV_X64_MSR_SYNDBG_OPTIONS 0x400000FF

+#define HV_X64_SYNDBG_OPTION_USE_HCALLS BIT(2)
+
/* Hyper-V guest crash notification MSR's */
#define HV_X64_MSR_CRASH_P0 0x40000100
#define HV_X64_MSR_CRASH_P1 0x40000101
@@ -392,6 +394,9 @@ struct hv_tsc_emulation_status {
#define HVCALL_SEND_IPI_EX 0x0015
#define HVCALL_POST_MESSAGE 0x005c
#define HVCALL_SIGNAL_EVENT 0x005d
+#define HVCALL_POST_DEBUG_DATA 0x0069
+#define HVCALL_RETRIEVE_DEBUG_DATA 0x006a
+#define HVCALL_RESET_DEBUG_SESSION 0x006b
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d657a312004a..52517e11e643 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1800,6 +1800,23 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
}
ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
break;
+ case HVCALL_POST_DEBUG_DATA:
+ case HVCALL_RETRIEVE_DEBUG_DATA:
+ case HVCALL_RESET_DEBUG_SESSION: {
+ struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+ if (!(syndbg->options & HV_X64_SYNDBG_OPTION_USE_HCALLS)) {
+ ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
+ break;
+ }
+ vcpu->run->exit_reason = KVM_EXIT_HYPERV;
+ vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
+ vcpu->run->hyperv.u.hcall.input = param;
+ vcpu->run->hyperv.u.hcall.params[0] = ingpa;
+ vcpu->run->hyperv.u.hcall.params[1] = outgpa;
+ vcpu->arch.complete_userspace_io =
+ kvm_hv_hypercall_complete_userspace;
+ return 0;
+ }
default:
ret = HV_STATUS_INVALID_HYPERCALL_CODE;
break;
--
2.24.1