[PATCH 5/7] KVM: TDX: Handle TDG.VP.VMCALL

Binbin Wu
2024-12-01T03:52:15Z

Convert TDG.VP.VMCALL<ReportFatalError> to KVM_EXIT_SYSTEM_EVENT with
a new type KVM_SYSTEM_EVENT_TDX_FATAL and forward it to userspace for
handling.

TD guest can use TDG.VP.VMCALL<ReportFatalError> to report the fatal
error it has experienced. This hypercall is special because TD guest
is requesting a termination with the error information, KVM needs to
forward the hypercall to userspace anyway, KVM doesn't do sanity checks
and let userspace decide what to do.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
---
Hypercalls exit to userspace breakout:
- New added.
Implement one of the hypercalls need to exit to userspace for handling after
reverting "KVM: TDX: Add KVM Exit for TDX TDG.VP.VMCALL", which tries to resolve
Sean's comment.
https://lore.kernel.org/kvm/Zg18ul8Q4PGQMWam@google.com/
- Use TDVMCALL_STATUS prefix for TDX call status codes (Binbin)
---
Documentation/virt/kvm/api.rst | 8 ++++++
arch/x86/kvm/vmx/tdx.c | 50 ++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 1 +
3 files changed, 59 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index edc070c6e19b..bb39da72c647 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6815,6 +6815,7 @@ should put the acknowledged interrupt vector into the 'epr' field.
#define KVM_SYSTEM_EVENT_WAKEUP 4
#define KVM_SYSTEM_EVENT_SUSPEND 5
#define KVM_SYSTEM_EVENT_SEV_TERM 6
+ #define KVM_SYSTEM_EVENT_TDX_FATAL 7
__u32 type;
__u32 ndata;
__u64 data[16];
@@ -6841,6 +6842,13 @@ Valid values for 'type' are:
reset/shutdown of the VM.
- KVM_SYSTEM_EVENT_SEV_TERM -- an AMD SEV guest requested termination.
The guest physical address of the guest's GHCB is stored in `data[0]`.
+ - KVM_SYSTEM_EVENT_TDX_FATAL -- an TDX guest requested termination.
+ The error codes of the guest's GHCI is stored in `data[0]`.
+ If the bit 63 of `data[0]` is set, it indicates there is TD specified
+ additional information provided in a page, which is shared memory. The
+ guest physical address of the information page is stored in `data[1]`.
+ An optional error message is provided by `data[2]` ~ `data[9]`, which is
+ byte sequence, LSB filled first. Typically, ASCII code(0x20-0x7e) is filled.
- KVM_SYSTEM_EVENT_WAKEUP -- the exiting vCPU is in a suspended state and
KVM has recognized a wakeup event. Userspace may honor this event by
marking the exiting vCPU as runnable, or deny it and call KVM_RUN again.
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 553f4cbe0693..a79f9ca962d1 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1093,6 +1093,54 @@ static int tdx_map_gpa(struct kvm_vcpu *vcpu)
return 1;
}

+static int tdx_report_fatal_error(struct kvm_vcpu *vcpu)
+{
+ u64 reg_mask = kvm_rcx_read(vcpu);
+ u64* opt_regs;
+
+ /*
+ * Skip sanity checks and let userspace decide what to do if sanity
+ * checks fail.
+ */
+ vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
+ vcpu->run->system_event.type = KVM_SYSTEM_EVENT_TDX_FATAL;
+ vcpu->run->system_event.ndata = 10;
+ /* Error codes. */
+ vcpu->run->system_event.data[0] = tdvmcall_a0_read(vcpu);
+ /* GPA of additional information page. */
+ vcpu->run->system_event.data[1] = tdvmcall_a1_read(vcpu);
+ /* Information passed via registers (up to 64 bytes). */
+ opt_regs = &vcpu->run->system_event.data[2];
+
+#define COPY_REG(REG, MASK) \
+ do { \
+ if (reg_mask & MASK) \
+ *opt_regs = kvm_ ## REG ## _read(vcpu); \
+ else \
+ *opt_regs = 0; \
+ opt_regs++; \
+ } while (0)
+
+ /* The order is defined in GHCI. */
+ COPY_REG(r14, BIT_ULL(14));
+ COPY_REG(r15, BIT_ULL(15));
+ COPY_REG(rbx, BIT_ULL(3));
+ COPY_REG(rdi, BIT_ULL(7));
+ COPY_REG(rsi, BIT_ULL(6));
+ COPY_REG(r8, BIT_ULL(8));
+ COPY_REG(r9, BIT_ULL(9));
+ COPY_REG(rdx, BIT_ULL(2));
+
+ /*
+ * Set the status code according to GHCI spec, although the vCPU may
+ * not return back to guest.
+ */
+ tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_SUCCESS);
+
+ /* Forward request to userspace. */
+ return 0;
+}
+
static int handle_tdvmcall(struct kvm_vcpu *vcpu)
{
if (tdvmcall_exit_type(vcpu))
@@ -1101,6 +1149,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
switch (tdvmcall_leaf(vcpu)) {
case TDVMCALL_MAP_GPA:
return tdx_map_gpa(vcpu);
+ case TDVMCALL_REPORT_FATAL_ERROR:
+ return tdx_report_fatal_error(vcpu);
default:
break;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 637efc055145..c173c8dfcf83 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -375,6 +375,7 @@ struct kvm_run {
#define KVM_SYSTEM_EVENT_WAKEUP 4
#define KVM_SYSTEM_EVENT_SUSPEND 5
#define KVM_SYSTEM_EVENT_SEV_TERM 6
+#define KVM_SYSTEM_EVENT_TDX_FATAL 7
__u32 type;
__u32 ndata;
union {
--
2.46.0