On 22/08/19 15:17, Yang Weijiang wrote: > On Tue, Aug 20, 2019 at 09:44:35PM +0800, Yang Weijiang wrote: >> On Mon, Aug 19, 2019 at 05:04:23PM +0200, Paolo Bonzini wrote: >>> fast_page_fault should never trigger an SPP userspace exit on its own, >>> all the SPP handling should go through handle_spp. > Hi, Paolo, > According to the latest SDM(28.2.4), handle_spp only handles SPPT miss and SPPT > misconfig(exit_reason==66), subpage write access violation causes EPT violation, > so have to deal with the two cases into handlers. Ok, so this part has to remain, though you do have to save/restore PT_SPP_MASK according to the rest of the email. Paolo >>> So I think that when KVM wants to write-protect the whole page >>> (wrprot_ad_disabled_spte) it must also clear PT_SPP_MASK; for example it >>> could save it in bit 53 (PT64_SECOND_AVAIL_BITS_SHIFT + 1). If the >>> saved bit is set, fast_page_fault must then set PT_SPP_MASK instead of >>> PT_WRITABLE_MASK.
