KVM: MMU: unify slots_lock usage

Unify slots_lock acquision around vcpu_run(). This is simpler and less
error-prone.

Also fix some callsites that were not grabbing the lock properly.

[avi: drop slots_lock while in guest mode to avoid holding the lock
      for indefinite periods]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/mmu.c

@@ -1204,8 +1204,6 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 
 	struct page *page;
 
-	down_read(&vcpu->kvm->slots_lock);
-
 	down_read(&current->mm->mmap_sem);
 	if (is_largepage_backed(vcpu, gfn & ~(KVM_PAGES_PER_HPAGE-1))) {
 		gfn &= ~(KVM_PAGES_PER_HPAGE-1);
@@ -1218,7 +1216,6 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 	/* mmio */
 	if (is_error_page(page)) {
 		kvm_release_page_clean(page);
-		up_read(&vcpu->kvm->slots_lock);
 		return 1;
 	}
 
@@ -1228,7 +1225,6 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
 			 PT32E_ROOT_LEVEL);
 	spin_unlock(&vcpu->kvm->mmu_lock);
 
-	up_read(&vcpu->kvm->slots_lock);
 
 	return r;
 }
@@ -1376,17 +1372,16 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
 		largepage = 1;
 	}
 	page = gfn_to_page(vcpu->kvm, gfn);
+	up_read(&current->mm->mmap_sem);
 	if (is_error_page(page)) {
 		kvm_release_page_clean(page);
-		up_read(&current->mm->mmap_sem);
 		return 1;
 	}
 	spin_lock(&vcpu->kvm->mmu_lock);
 	kvm_mmu_free_some_pages(vcpu);
 	r = __direct_map(vcpu, gpa, error_code & PFERR_WRITE_MASK,
 			 largepage, gfn, page, TDP_ROOT_LEVEL);
 	spin_unlock(&vcpu->kvm->mmu_lock);
-	up_read(&current->mm->mmap_sem);
 
 	return r;
 }
@@ -1808,9 +1803,7 @@ int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
 	gpa_t gpa;
 	int r;
 
-	down_read(&vcpu->kvm->slots_lock);
 	gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, gva);
-	up_read(&vcpu->kvm->slots_lock);
 
 	spin_lock(&vcpu->kvm->mmu_lock);
 	r = kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT);
@@ -2063,7 +2056,7 @@ static int kvm_pv_mmu_write(struct kvm_vcpu *vcpu,
 	if (r)
 		return r;
 
-	if (!__emulator_write_phys(vcpu, addr, &value, bytes))
+	if (!emulator_write_phys(vcpu, addr, &value, bytes))
 		return -EFAULT;
 
 	return 1;
@@ -2127,7 +2120,6 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
 	int r;
 	struct kvm_pv_mmu_op_buffer buffer;
 
-	down_read(&vcpu->kvm->slots_lock);
 	down_read(&current->mm->mmap_sem);
 
 	buffer.ptr = buffer.buf;
@@ -2150,7 +2142,6 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
 out:
 	*ret = buffer.processed;
 	up_read(&current->mm->mmap_sem);
-	up_read(&vcpu->kvm->slots_lock);
 	return r;
 }
 

arch/x86/kvm/paging_tmpl.h

@@ -388,7 +388,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	if (r)
 		return r;
 
-	down_read(&vcpu->kvm->slots_lock);
 	/*
 	 * Look up the shadow pte for the faulting address.
 	 */
@@ -402,7 +401,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 		pgprintk("%s: guest page fault\n", __func__);
 		inject_page_fault(vcpu, addr, walker.error_code);
 		vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
-		up_read(&vcpu->kvm->slots_lock);
 		return 0;
 	}
 
@@ -422,7 +420,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	if (is_error_page(page)) {
 		pgprintk("gfn %x is mmio\n", walker.gfn);
 		kvm_release_page_clean(page);
-		up_read(&vcpu->kvm->slots_lock);
 		return 1;
 	}
 
@@ -440,7 +437,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	++vcpu->stat.pf_fixed;
 	kvm_mmu_audit(vcpu, "post page fault (fixed)");
 	spin_unlock(&vcpu->kvm->mmu_lock);
-	up_read(&vcpu->kvm->slots_lock);
 
 	return write_pt;
 }

arch/x86/kvm/vmx.c

@@ -1505,7 +1505,6 @@ static int init_rmode_tss(struct kvm *kvm)
 	int ret = 0;
 	int r;
 
-	down_read(&kvm->slots_lock);
 	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
 	if (r < 0)
 		goto out;
@@ -1528,7 +1527,6 @@ static int init_rmode_tss(struct kvm *kvm)
 
 	ret = 1;
 out:
-	up_read(&kvm->slots_lock);
 	return ret;
 }
 
@@ -1730,6 +1728,7 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 	u64 msr;
 	int ret;
 
+	down_read(&vcpu->kvm->slots_lock);
 	if (!init_rmode_tss(vmx->vcpu.kvm)) {
 		ret = -ENOMEM;
 		goto out;
@@ -1833,9 +1832,10 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 
 	vpid_sync_vcpu_all(vmx);
 
-	return 0;
+	ret = 0;
 
 out:
+	up_read(&vcpu->kvm->slots_lock);
 	return ret;
 }