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Shutemov" Content-Type: text/plain; charset="us-ascii" On Thu, Feb 06, 2025, Vishal Annapurve wrote: > Direct HLT instruction execution causes #VEs for TDX VMs which is routed > to hypervisor via TDCALL. safe_halt() routines execute HLT in STI-shadow > so IRQs need to remain disabled until the TDCALL to ensure that pending > IRQs are correctly treated as wake events. > > Emit warning and fail emulation if IRQs are enabled during HLT #VE handling > to avoid running into scenarios where IRQ wake events are lost resulting in > indefinite HLT execution times. > > Reviewed-by: Kirill A. Shutemov @linux.intel.com> > Signed-off-by: Vishal Annapurve > --- > arch/x86/coco/tdx/tdx.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c > index 5e68758666a4..ed6738ea225c 100644 > --- a/arch/x86/coco/tdx/tdx.c > +++ b/arch/x86/coco/tdx/tdx.c > @@ -393,6 +393,11 @@ static int handle_halt(struct ve_info *ve) > { > const bool irq_disabled = irqs_disabled(); > > + if (!irq_disabled) { Wrap the check with WARN_ONCE(), doing so adds an unlikely to the unlikely scenario. > + WARN_ONCE(1, "HLT instruction emulation unsafe with irqs enabled\n"); Newline is redundant, the WARN does that for you. IMO, it's also worth adding a comment, because this is like the fifth time "safe halt" has come up in the context of TDX. E.g. /* * HLT with IRQs enabled is unsafe, as an IRQ that is intended to be a * wake event may be consumed before requesting HLT emulation, leaving * the vCPU blocking indefinitely. */ if (WARN_ONCE(!irq_disabled, "HLT emulation with IRQs enabled")) return -EIO;