Re: [PATCH RESEND v4 7/9] KVM: VMX: Handle SPP induced vmexit and page fault
From: Yang Weijiang
Date: Thu Aug 22 2019 - 20:25:01 EST
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.
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.