On 3/26/21 7:40 PM, Andy Lutomirski wrote:
On Mar 26, 2021, at 5:18 PM, Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppusw...@linux.intel.com> wrote:
In non-root TDX guest mode, MWAIT, MONITOR and WBINVD instructions
are not supported. So handle #VE due to these instructions as no ops.
These should at least be WARN.
I will change it to WARN.
Does TDX send #UD if these instructions have the wrong CPL?
No, TDX does not trigger #UD for these instructions.
If the #VE came from user mode, we should send an appropriate signal instead.
It will be mapped into #GP(0) fault. This should be enough notification right?
Signed-off-by: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppusw...@linux.intel.com>
Reviewed-by: Andi Kleen <a...@linux.intel.com>
---
Changes since previous series:
* Suppressed MWAIT feature as per Andi's comment.
* Added warning debug log for MWAIT #VE exception.
arch/x86/kernel/tdx.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index e936b2f88bf6..fb7d22b846fc 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -308,6 +308,9 @@ void __init tdx_early_init(void)
setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
+ /* MWAIT is not supported in TDX platform, so suppress it */
+ setup_clear_cpu_cap(X86_FEATURE_MWAIT);
+
tdg_get_info();
pv_ops.irq.safe_halt = tdg_safe_halt;
@@ -362,6 +365,26 @@ int tdg_handle_virtualization_exception(struct pt_regs
*regs,
case EXIT_REASON_EPT_VIOLATION:
ve->instr_len = tdg_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_MONITOR_INSTRUCTION:
+ /* Handle as nops. */
+ break;
+ case EXIT_REASON_MWAIT_INSTRUCTION:
+ /* MWAIT is supressed, not supposed to reach here. */
+ pr_warn("MWAIT unexpected #VE Exception\n");
+ return -EFAULT;
default:
pr_warn("Unexpected #VE: %d\n", ve->exit_reason);
return -EFAULT;
--
2.25.1
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
