KVM: MMU: prefetch ptes when intercepted guest #PF
Support prefetch ptes when intercept guest #PF, avoid to #PF by later
access
If we meet any failure in the prefetch path, we will exit it and
not try other ptes to avoid become heavy path
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 51ef909..872ff26 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -310,6 +310,77 @@
return r || curr_pte != gw->ptes[level - 1];
}
+static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
+{
+ struct kvm_mmu_page *sp;
+ pt_element_t gptep[PTE_PREFETCH_NUM];
+ gpa_t first_pte_gpa;
+ int offset = 0, i;
+ u64 *spte;
+
+ sp = page_header(__pa(sptep));
+
+ if (sp->role.level > PT_PAGE_TABLE_LEVEL)
+ return;
+
+ if (sp->role.direct)
+ return __direct_pte_prefetch(vcpu, sp, sptep);
+
+ i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
+
+ if (PTTYPE == 32)
+ offset = sp->role.quadrant << PT64_LEVEL_BITS;
+
+ first_pte_gpa = gfn_to_gpa(sp->gfn) +
+ (offset + i) * sizeof(pt_element_t);
+
+ if (kvm_read_guest_atomic(vcpu->kvm, first_pte_gpa, gptep,
+ sizeof(gptep)) < 0)
+ return;
+
+ spte = sp->spt + i;
+
+ for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
+ pt_element_t gpte;
+ unsigned pte_access;
+ gfn_t gfn;
+ pfn_t pfn;
+ bool dirty;
+
+ if (spte == sptep)
+ continue;
+
+ if (*spte != shadow_trap_nonpresent_pte)
+ continue;
+
+ gpte = gptep[i];
+
+ if (!is_present_gpte(gpte) ||
+ is_rsvd_bits_set(vcpu, gpte, PT_PAGE_TABLE_LEVEL)) {
+ if (!sp->unsync)
+ __set_spte(spte, shadow_notrap_nonpresent_pte);
+ continue;
+ }
+
+ if (!(gpte & PT_ACCESSED_MASK))
+ continue;
+
+ pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
+ gfn = gpte_to_gfn(gpte);
+ dirty = is_dirty_gpte(gpte);
+ pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn,
+ (pte_access & ACC_WRITE_MASK) && dirty);
+ if (is_error_pfn(pfn)) {
+ kvm_release_pfn_clean(pfn);
+ break;
+ }
+
+ mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0,
+ dirty, NULL, PT_PAGE_TABLE_LEVEL, gfn,
+ pfn, true, true);
+ }
+}
+
/*
* Fetch a shadow pte for a specific level in the paging hierarchy.
*/
@@ -391,6 +462,7 @@
mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access,
user_fault, write_fault, dirty, ptwrite, it.level,
gw->gfn, pfn, false, true);
+ FNAME(pte_prefetch)(vcpu, it.sptep);
return it.sptep;