On Thu, Jun 22, 2023 at 11:28:22PM +0000, "Huang, Kai" <kai.huang@xxxxxxxxx> wrote: > On Thu, 2023-06-22 at 16:16 -0700, Yamahata, Isaku wrote: > > The upper 32 bits of error code are discarded at kvm_mmu_page_fault() > > by lower_32_bits(). Now it's passed down as full 64 bits. > > Because only FNAME(page_fault) depends on it, move lower_32_bits() into > > FNAME(page_fault). > > I haven't looked into the code yet, but the last sentence around > FNAME(page_fault) doesn't make a lot sense IIUC? > > For instance, we can have a shadow EPT table when EPT is enabled in L0 and > exposed to L1. If we want to pass 64-bit error code to the handler, how can > FRAME(page_fault)() depend on the lower 32-bit value? Probably "depend" was too strong. In short, I wanted to not change the value passed down as error_code from FNAME(page_fault). FNAME(page_fault) calls helper function to walk page tables. Some check PFERR_IMPLICIT_ACCESS_MASK(48 bit). If we don't mask lower_32_bits(), it can pass accidentally the bit. Maybe we can audit the code carefully to check if IMPLICIT_ACCESS bit doesn't matter or fix it. But I don't want to do it with this patch series. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
