On Thu, Sep 1, 2022 at 9:47 AM David Matlack <dmatlack@xxxxxxxxxx> wrote: > On Tue, Aug 30, 2022 at 3:12 AM Huang, Kai <kai.huang@xxxxxxxxx> wrote: > > On Fri, 2022-08-26 at 16:12 -0700, David Matlack wrote: [...] > > > +#else > > > +/* TDP MMU is not supported on 32-bit KVM. */ > > > +const bool tdp_mmu_enabled; > > > +#endif > > > + > > > > I am not sure by using 'const bool' the compile will always omit the function > > call? I did some experiment on my 64-bit system and it seems if we don't use > > any -O option then the generated code still does function call. > > > > How about just (if it works): > > > > #define tdp_mmu_enabled false > > I can give it a try. By the way, I wonder if the existing code > compiles without -O. The existing code relies on a static inline > function returning false on 32-bit KVM, which doesn't seem like it > would be any easier for the compiler to optimize out than a const > bool. But who knows. Actually, how did you compile without -O and is that a supported use-case? I tried both CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE (-O2) and CONFIG_CC_OPTIMIZE_FOR_SIZE (-Os) and did not encounter any issues building 32-bit KVM with this series.
