On Thu, Aug 22, 2019 at 06:38:41PM +0200, Paolo Bonzini wrote: > 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 > Got it, thanks! > >>> 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.
