From 134291bf3cb434a9039298ba6b15ef33e65ba542 Mon Sep 17 00:00:00 2001 From: Takuya Yoshikawa Date: Fri, 1 Jul 2011 01:34:56 +0900 Subject: [PATCH] KVM: MMU: Clean up the error handling of walk_addr_generic() Avoid two step jump to the error handling part. This eliminates the use of the variables present and rsvd_fault. We also use the const type qualifier to show that write/user/fetch_fault do not change in the function. Both of these were suggested by Ingo Molnar. Cc: Ingo Molnar Signed-off-by: Takuya Yoshikawa Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/paging_tmpl.h | 82 +++++++++++++++----------------------- 1 file changed, 32 insertions(+), 50 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 1caeb4d22e0..f0746d27e33 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -125,18 +125,17 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, gfn_t table_gfn; unsigned index, pt_access, uninitialized_var(pte_access); gpa_t pte_gpa; - bool eperm, present, rsvd_fault; - int offset, write_fault, user_fault, fetch_fault; - - write_fault = access & PFERR_WRITE_MASK; - user_fault = access & PFERR_USER_MASK; - fetch_fault = access & PFERR_FETCH_MASK; + bool eperm; + int offset; + const int write_fault = access & PFERR_WRITE_MASK; + const int user_fault = access & PFERR_USER_MASK; + const int fetch_fault = access & PFERR_FETCH_MASK; + u16 errcode = 0; trace_kvm_mmu_pagetable_walk(addr, write_fault, user_fault, fetch_fault); walk: - present = true; - eperm = rsvd_fault = false; + eperm = false; walker->level = mmu->root_level; pte = mmu->get_cr3(vcpu); @@ -144,10 +143,8 @@ walk: if (walker->level == PT32E_ROOT_LEVEL) { pte = kvm_pdptr_read_mmu(vcpu, mmu, (addr >> 30) & 3); trace_kvm_mmu_paging_element(pte, walker->level); - if (!is_present_gpte(pte)) { - present = false; + if (!is_present_gpte(pte)) goto error; - } --walker->level; } #endif @@ -170,35 +167,27 @@ walk: real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn), PFERR_USER_MASK|PFERR_WRITE_MASK); - if (unlikely(real_gfn == UNMAPPED_GVA)) { - present = false; - break; - } + if (unlikely(real_gfn == UNMAPPED_GVA)) + goto error; real_gfn = gpa_to_gfn(real_gfn); host_addr = gfn_to_hva(vcpu->kvm, real_gfn); - if (unlikely(kvm_is_error_hva(host_addr))) { - present = false; - break; - } + if (unlikely(kvm_is_error_hva(host_addr))) + goto error; ptep_user = (pt_element_t __user *)((void *)host_addr + offset); - if (unlikely(__copy_from_user(&pte, ptep_user, sizeof(pte)))) { - present = false; - break; - } + if (unlikely(__copy_from_user(&pte, ptep_user, sizeof(pte)))) + goto error; trace_kvm_mmu_paging_element(pte, walker->level); - if (unlikely(!is_present_gpte(pte))) { - present = false; - break; - } + if (unlikely(!is_present_gpte(pte))) + goto error; if (unlikely(is_rsvd_bits_set(&vcpu->arch.mmu, pte, walker->level))) { - rsvd_fault = true; - break; + errcode |= PFERR_RSVD_MASK | PFERR_PRESENT_MASK; + goto error; } if (unlikely(write_fault && !is_writable_pte(pte) @@ -213,17 +202,15 @@ walk: eperm = true; #endif - if (!eperm && !rsvd_fault - && unlikely(!(pte & PT_ACCESSED_MASK))) { + if (!eperm && unlikely(!(pte & PT_ACCESSED_MASK))) { int ret; trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte)); ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, pte, pte|PT_ACCESSED_MASK); - if (unlikely(ret < 0)) { - present = false; - break; - } else if (ret) + if (unlikely(ret < 0)) + goto error; + else if (ret) goto walk; mark_page_dirty(vcpu->kvm, table_gfn); @@ -276,8 +263,10 @@ walk: --walker->level; } - if (unlikely(!present || eperm || rsvd_fault)) + if (unlikely(eperm)) { + errcode |= PFERR_PRESENT_MASK; goto error; + } if (write_fault && unlikely(!is_dirty_gpte(pte))) { int ret; @@ -285,10 +274,9 @@ walk: trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte)); ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, pte, pte|PT_DIRTY_MASK); - if (unlikely(ret < 0)) { - present = false; + if (unlikely(ret < 0)) goto error; - } else if (ret) + else if (ret) goto walk; mark_page_dirty(vcpu->kvm, table_gfn); @@ -303,20 +291,14 @@ walk: return 1; error: - walker->fault.vector = PF_VECTOR; - walker->fault.error_code_valid = true; - walker->fault.error_code = 0; - if (present) - walker->fault.error_code |= PFERR_PRESENT_MASK; - - walker->fault.error_code |= write_fault | user_fault; - + errcode |= write_fault | user_fault; if (fetch_fault && (mmu->nx || kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))) - walker->fault.error_code |= PFERR_FETCH_MASK; - if (rsvd_fault) - walker->fault.error_code |= PFERR_RSVD_MASK; + errcode |= PFERR_FETCH_MASK; + walker->fault.vector = PF_VECTOR; + walker->fault.error_code_valid = true; + walker->fault.error_code = errcode; walker->fault.address = addr; walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu; -- 2.46.0