diff options
| -rw-r--r-- | arch/x86/kvm/mmu.c | 13 | ||||
| -rw-r--r-- | arch/x86/kvm/paging_tmpl.h | 35 |
2 files changed, 38 insertions, 10 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 2a3c8909b144..54fc61e4b061 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2380,15 +2380,10 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, if (pte_access & ACC_WRITE_MASK) { /* - * There are two cases: - * - the one is other vcpu creates new sp in the window - * between mapping_level() and acquiring mmu-lock. - * - the another case is the new sp is created by itself - * (page-fault path) when guest uses the target gfn as - * its page table. - * Both of these cases can be fixed by allowing guest to - * retry the access, it will refault, then we can establish - * the mapping by using small page. + * Other vcpu creates new sp in the window between + * mapping_level() and acquiring mmu-lock. We can + * allow guest to retry the access, the mapping can + * be fixed if guest refault. */ if (level > PT_PAGE_TABLE_LEVEL && has_wrprotected_page(vcpu->kvm, gfn, level)) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 0d2e7113cb52..3d1a35237dbf 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -487,6 +487,38 @@ out_gpte_changed: return 0; } + /* + * To see whether the mapped gfn can write its page table in the current + * mapping. + * + * It is the helper function of FNAME(page_fault). When guest uses large page + * size to map the writable gfn which is used as current page table, we should + * force kvm to use small page size to map it because new shadow page will be + * created when kvm establishes shadow page table that stop kvm using large + * page size. Do it early can avoid unnecessary #PF and emulation. + * + * Note: the PDPT page table is not checked for PAE-32 bit guest. It is ok + * since the PDPT is always shadowed, that means, we can not use large page + * size to map the gfn which is used as PDPT. + */ +static bool +FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu, + struct guest_walker *walker, int user_fault) +{ + int level; + gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1); + + if (!(walker->pte_access & ACC_WRITE_MASK || + (!is_write_protection(vcpu) && !user_fault))) + return false; + + for (level = walker->level; level <= walker->max_level; level++) + if (!((walker->gfn ^ walker->table_gfn[level - 1]) & mask)) + return true; + + return false; +} + /* * Page fault handler. There are several causes for a page fault: * - there is no shadow pte for the guest pte @@ -541,7 +573,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, } if (walker.level >= PT_DIRECTORY_LEVEL) - force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn); + force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn) + || FNAME(is_self_change_mapping)(vcpu, &walker, user_fault); else force_pt_level = 1; if (!force_pt_level) { |