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Subject[RFC v1 13/26] x86/tdx: Handle MWAIT, MONITOR and WBINVD
Date
In non-root TDX guest mode, MWAIT, MONITOR and WBINVD instructions
are not supported. So handle #VE due to these instructions as no ops.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/kernel/tdx.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index eff58329751e..8d1d7555fb56 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -451,6 +451,23 @@ int tdx_handle_virtualization_exception(struct pt_regs *regs,
case EXIT_REASON_EPT_VIOLATION:
ve->instr_len = tdx_handle_mmio(regs, ve);
break;
+ /*
+ * Per Guest-Host-Communication Interface (GHCI) for Intel Trust
+ * Domain Extensions (Intel TDX) specification, sec 2.4,
+ * some instructions that unconditionally cause #VE (such as WBINVD,
+ * MONITOR, MWAIT) do not have corresponding TDCALL
+ * [TDG.VP.VMCALL <Instruction>] leaves, since the TD has been designed
+ * with no deterministic way to confirm the result of those operations
+ * performed by the host VMM. In those cases, the goal is for the TD
+ * #VE handler to increment the RIP appropriately based on the VE
+ * information provided via TDCALL.
+ */
+ case EXIT_REASON_WBINVD:
+ pr_warn_once("WBINVD #VE Exception\n");
+ case EXIT_REASON_MWAIT_INSTRUCTION:
+ case EXIT_REASON_MONITOR_INSTRUCTION:
+ /* Handle as nops. */
+ break;
default:
pr_warn("Unexpected #VE: %d\n", ve->exit_reason);
return -EFAULT;
--
2.25.1
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