On Thu, Jan 30, 2025 at 11:45:01AM -0800, Vishal Annapurve wrote: > On Thu, Jan 30, 2025 at 10:48 AM Kirill A. Shutemov > <kirill@xxxxxxxxxxxxx> wrote: > > ... > > > > > > > > I think it is worth to putting this into a separate patch and not > > > > backport. The rest of the patch is bugfix and this doesn't belong. > > > > > > > > Otherwise, looks good to me: > > > > > > > > Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>@linux.intel.com> > > > > > > > > -- > > > > Kiryl Shutsemau / Kirill A. Shutemov > > > > > > Thanks Kirill for the review. > > > > > > Thinking more about this fix, now I am wondering why the efforts [1] > > > to move halt/safe_halt under CONFIG_PARAVIRT were abandoned. Currently > > > proposed fix is incomplete as it would not handle scenarios where > > > CONFIG_PARAVIRT_XXL is disabled. I am tilting towards reviving [1] and > > > requiring CONFIG_PARAVIRT for TDX VMs. WDYT? > > > > > > [1] https://lore.kernel.org/lkml/20210517235008.257241-1-sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx/ > > > > Many people dislike paravirt callbacks. We tried to avoid relying on them > > for core TDX enabling. > > > > Can you explain the issue you see with CONFIG_PARAVIRT_XXL being disabled? > > I don't think I follow. > > Relevant callers of *_safe_halt() are: > 1) kvm_wait() -> safe_halt() -> raw_safe_halt() -> arch_safe_halt() Okay, I didn't realized that CONFIG_PARAVIRT_SPINLOCKS doesn't depend on CONFIG_PARAVIRT_XXL. It would be interesting to check if paravirtualized spinlocks make sense for TDX given the cost of TD exit. Maybe we should avoid advertising KVM_FEATURE_PV_UNHALT to the TDX guests? > 2) acpi_safe_halt() -> safe_halt() -> raw_safe_halt() -> arch_safe_halt() Have you checked why you get there? I don't see a reason for TDX guest to get into ACPI idle stuff. We don't have C-states to manage. -- Kiryl Shutsemau / Kirill A. Shutemov
