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Commit 72dc67a6 authored by Izik Eidus's avatar Izik Eidus Committed by Avi Kivity
Browse files

KVM: remove the usage of the mmap_sem for the protection of the memory slots. 



This patch replaces the mmap_sem lock for the memory slots with a new
kvm private lock, it is needed beacuse untill now there were cases where
kvm accesses user memory while holding the mmap semaphore.

Signed-off-by: default avatarIzik Eidus <izike@qumranet.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent c7ac679c

arch/x86/kvm/mmu.c

+20 −4
Original line number Diff line number Diff line
@@ -876,11 +876,18 @@ static void page_header_update_slot(struct kvm *kvm, void *pte, gfn_t gfn) 


struct page *gva_to_page(struct kvm_vcpu *vcpu, gva_t gva)

{

	struct page *page;



	gpa_t gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, gva);



	if (gpa == UNMAPPED_GVA)

		return NULL;

	return gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);



	down_read(&current->mm->mmap_sem);

	page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);

	up_read(&current->mm->mmap_sem);



	return page;

}



static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
@@ -1020,15 +1027,18 @@ 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);

	page = gfn_to_page(vcpu->kvm, gfn);

	up_read(&current->mm->mmap_sem);



	spin_lock(&vcpu->kvm->mmu_lock);

	kvm_mmu_free_some_pages(vcpu);

	r = __nonpaging_map(vcpu, v, write, gfn, page);

	spin_unlock(&vcpu->kvm->mmu_lock);



	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	return r;

}
@@ -1362,6 +1372,7 @@ static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, 
	gfn_t gfn;

	int r;

	u64 gpte = 0;

	struct page *page;



	if (bytes != 4 && bytes != 8)

		return;
@@ -1389,6 +1400,11 @@ static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, 
	if (!is_present_pte(gpte))

		return;

	gfn = (gpte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;



	down_read(&current->mm->mmap_sem);

	page = gfn_to_page(vcpu->kvm, gfn);

	up_read(&current->mm->mmap_sem);



	vcpu->arch.update_pte.gfn = gfn;

	vcpu->arch.update_pte.page = gfn_to_page(vcpu->kvm, gfn);

}
@@ -1496,9 +1512,9 @@ int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva) 
	gpa_t gpa;

	int r;



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, gva);

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	spin_lock(&vcpu->kvm->mmu_lock);

	r = kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT);

arch/x86/kvm/paging_tmpl.h

+9 −4
Original line number Diff line number Diff line
@@ -91,7 +91,10 @@ static bool FNAME(cmpxchg_gpte)(struct kvm *kvm, 
	pt_element_t *table;

	struct page *page;



	down_read(&current->mm->mmap_sem);

	page = gfn_to_page(kvm, table_gfn);

	up_read(&current->mm->mmap_sem);



	table = kmap_atomic(page, KM_USER0);



	ret = CMPXCHG(&table[index], orig_pte, new_pte);
@@ -378,7 +381,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, 
	if (r)

		return r;



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	/*

	 * Look up the shadow pte for the faulting address.

	 */
@@ -392,11 +395,13 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, 
		pgprintk("%s: guest page fault\n", __FUNCTION__);

		inject_page_fault(vcpu, addr, walker.error_code);

		vcpu->arch.last_pt_write_count = 0; /* reset fork detector */

		up_read(&current->mm->mmap_sem);

		up_read(&vcpu->kvm->slots_lock);

		return 0;

	}



	down_read(&current->mm->mmap_sem);

	page = gfn_to_page(vcpu->kvm, walker.gfn);

	up_read(&current->mm->mmap_sem);



	spin_lock(&vcpu->kvm->mmu_lock);

	kvm_mmu_free_some_pages(vcpu);
@@ -413,14 +418,14 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, 
	 */

	if (shadow_pte && is_io_pte(*shadow_pte)) {

		spin_unlock(&vcpu->kvm->mmu_lock);

		up_read(&current->mm->mmap_sem);

		up_read(&vcpu->kvm->slots_lock);

		return 1;

	}



	++vcpu->stat.pf_fixed;

	kvm_mmu_audit(vcpu, "post page fault (fixed)");

	spin_unlock(&vcpu->kvm->mmu_lock);

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	return write_pt;

}

arch/x86/kvm/vmx.c

+5 −2
Original line number Diff line number Diff line
@@ -1477,7 +1477,7 @@ static int alloc_apic_access_page(struct kvm *kvm) 
	struct kvm_userspace_memory_region kvm_userspace_mem;

	int r = 0;



	down_write(&current->mm->mmap_sem);

	down_write(&kvm->slots_lock);

	if (kvm->arch.apic_access_page)

		goto out;

	kvm_userspace_mem.slot = APIC_ACCESS_PAGE_PRIVATE_MEMSLOT;
@@ -1487,9 +1487,12 @@ static int alloc_apic_access_page(struct kvm *kvm) 
	r = __kvm_set_memory_region(kvm, &kvm_userspace_mem, 0);

	if (r)

		goto out;



	down_read(&current->mm->mmap_sem);

	kvm->arch.apic_access_page = gfn_to_page(kvm, 0xfee00);

	up_read(&current->mm->mmap_sem);

out:

	up_write(&current->mm->mmap_sem);

	up_write(&kvm->slots_lock);

	return r;

}

arch/x86/kvm/x86.c

+37 −28
Original line number Diff line number Diff line
@@ -184,7 +184,7 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3) 
	int ret;

	u64 pdpte[ARRAY_SIZE(vcpu->arch.pdptrs)];



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	ret = kvm_read_guest_page(vcpu->kvm, pdpt_gfn, pdpte,

				  offset * sizeof(u64), sizeof(pdpte));

	if (ret < 0) {
@@ -201,7 +201,7 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3) 


	memcpy(vcpu->arch.pdptrs, pdpte, sizeof(vcpu->arch.pdptrs));

out:

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	return ret;

}
@@ -215,13 +215,13 @@ static bool pdptrs_changed(struct kvm_vcpu *vcpu) 
	if (is_long_mode(vcpu) || !is_pae(vcpu))

		return false;



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	r = kvm_read_guest(vcpu->kvm, vcpu->arch.cr3 & ~31u, pdpte, sizeof(pdpte));

	if (r < 0)

		goto out;

	changed = memcmp(pdpte, vcpu->arch.pdptrs, sizeof(pdpte)) != 0;

out:

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	return changed;

}
@@ -359,7 +359,7 @@ void set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) 
		 */

	}



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	/*

	 * Does the new cr3 value map to physical memory? (Note, we

	 * catch an invalid cr3 even in real-mode, because it would
@@ -375,7 +375,7 @@ void set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) 
		vcpu->arch.cr3 = cr3;

		vcpu->arch.mmu.new_cr3(vcpu);

	}

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);

}

EXPORT_SYMBOL_GPL(set_cr3);
@@ -1232,12 +1232,12 @@ static int kvm_vm_ioctl_set_nr_mmu_pages(struct kvm *kvm, 
	if (kvm_nr_mmu_pages < KVM_MIN_ALLOC_MMU_PAGES)

		return -EINVAL;



	down_write(&current->mm->mmap_sem);

	down_write(&kvm->slots_lock);



	kvm_mmu_change_mmu_pages(kvm, kvm_nr_mmu_pages);

	kvm->arch.n_requested_mmu_pages = kvm_nr_mmu_pages;



	up_write(&current->mm->mmap_sem);

	up_write(&kvm->slots_lock);

	return 0;

}
@@ -1286,7 +1286,7 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm, 
	    < alias->target_phys_addr)

		goto out;



	down_write(&current->mm->mmap_sem);

	down_write(&kvm->slots_lock);



	p = &kvm->arch.aliases[alias->slot];

	p->base_gfn = alias->guest_phys_addr >> PAGE_SHIFT;
@@ -1300,7 +1300,7 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm, 


	kvm_mmu_zap_all(kvm);



	up_write(&current->mm->mmap_sem);

	up_write(&kvm->slots_lock);



	return 0;
@@ -1376,7 +1376,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, 
	struct kvm_memory_slot *memslot;

	int is_dirty = 0;



	down_write(&current->mm->mmap_sem);

	down_write(&kvm->slots_lock);



	r = kvm_get_dirty_log(kvm, log, &is_dirty);

	if (r)
@@ -1392,7 +1392,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, 
	}

	r = 0;

out:

	up_write(&current->mm->mmap_sem);

	up_write(&kvm->slots_lock);

	return r;

}
@@ -1570,7 +1570,7 @@ int emulator_read_std(unsigned long addr, 
	void *data = val;

	int r = X86EMUL_CONTINUE;



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	while (bytes) {

		gpa_t gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, addr);

		unsigned offset = addr & (PAGE_SIZE-1);
@@ -1592,7 +1592,7 @@ int emulator_read_std(unsigned long addr, 
		addr += tocopy;

	}

out:

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);

	return r;

}

EXPORT_SYMBOL_GPL(emulator_read_std);
@@ -1611,9 +1611,9 @@ static int emulator_read_emulated(unsigned long addr, 
		return X86EMUL_CONTINUE;

	}



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, addr);

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	/* For APIC access vmexit */

	if ((gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE)
@@ -1651,14 +1651,14 @@ static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa, 
{

	int ret;



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	ret = kvm_write_guest(vcpu->kvm, gpa, val, bytes);

	if (ret < 0) {

		up_read(&current->mm->mmap_sem);

		up_read(&vcpu->kvm->slots_lock);

		return 0;

	}

	kvm_mmu_pte_write(vcpu, gpa, val, bytes);

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);

	return 1;

}
@@ -1670,9 +1670,9 @@ static int emulator_write_emulated_onepage(unsigned long addr, 
	struct kvm_io_device *mmio_dev;

	gpa_t                 gpa;



	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, addr);

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);



	if (gpa == UNMAPPED_GVA) {

		kvm_inject_page_fault(vcpu, addr, 2);
@@ -1749,7 +1749,7 @@ static int emulator_cmpxchg_emulated(unsigned long addr, 
		char *kaddr;

		u64 val;



		down_read(&current->mm->mmap_sem);

		down_read(&vcpu->kvm->slots_lock);

		gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, addr);



		if (gpa == UNMAPPED_GVA ||
@@ -1760,13 +1760,17 @@ static int emulator_cmpxchg_emulated(unsigned long addr, 
			goto emul_write;



		val = *(u64 *)new;



		down_read(&current->mm->mmap_sem);

		page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);

		up_read(&current->mm->mmap_sem);



		kaddr = kmap_atomic(page, KM_USER0);

		set_64bit((u64 *)(kaddr + offset_in_page(gpa)), val);

		kunmap_atomic(kaddr, KM_USER0);

		kvm_release_page_dirty(page);

	emul_write:

		up_read(&current->mm->mmap_sem);

		up_read(&vcpu->kvm->slots_lock);

	}

#endif
@@ -2159,10 +2163,10 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, struct kvm_run *run, int in, 
		kvm_x86_ops->skip_emulated_instruction(vcpu);



	for (i = 0; i < nr_pages; ++i) {

		down_read(&current->mm->mmap_sem);

		down_read(&vcpu->kvm->slots_lock);

		page = gva_to_page(vcpu, address + i * PAGE_SIZE);

		vcpu->arch.pio.guest_pages[i] = page;

		up_read(&current->mm->mmap_sem);

		up_read(&vcpu->kvm->slots_lock);

		if (!page) {

			kvm_inject_gp(vcpu, 0);

			free_pio_guest_pages(vcpu);
@@ -2485,8 +2489,9 @@ static void vapic_enter(struct kvm_vcpu *vcpu) 


	down_read(&current->mm->mmap_sem);

	page = gfn_to_page(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);

	vcpu->arch.apic->vapic_page = page;

	up_read(&current->mm->mmap_sem);



	vcpu->arch.apic->vapic_page = page;

}



static void vapic_exit(struct kvm_vcpu *vcpu)
@@ -2959,9 +2964,9 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu, 
	gpa_t gpa;



	vcpu_load(vcpu);

	down_read(&current->mm->mmap_sem);

	down_read(&vcpu->kvm->slots_lock);

	gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, vaddr);

	up_read(&current->mm->mmap_sem);

	up_read(&vcpu->kvm->slots_lock);

	tr->physical_address = gpa;

	tr->valid = gpa != UNMAPPED_GVA;

	tr->writeable = 1;
@@ -3234,11 +3239,13 @@ int kvm_arch_set_memory_region(struct kvm *kvm, 
	 */

	if (!user_alloc) {

		if (npages && !old.rmap) {

			down_write(&current->mm->mmap_sem);

			memslot->userspace_addr = do_mmap(NULL, 0,

						     npages * PAGE_SIZE,

						     PROT_READ | PROT_WRITE,

						     MAP_SHARED | MAP_ANONYMOUS,

						     0);

			up_write(&current->mm->mmap_sem);



			if (IS_ERR((void *)memslot->userspace_addr))

				return PTR_ERR((void *)memslot->userspace_addr);
@@ -3246,8 +3253,10 @@ int kvm_arch_set_memory_region(struct kvm *kvm, 
			if (!old.user_alloc && old.rmap) {

				int ret;



				down_write(&current->mm->mmap_sem);

				ret = do_munmap(current->mm, old.userspace_addr,

						old.npages * PAGE_SIZE);

				up_write(&current->mm->mmap_sem);

				if (ret < 0)

					printk(KERN_WARNING

				       "kvm_vm_ioctl_set_memory_region: "

include/linux/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -107,6 +107,7 @@ struct kvm_memory_slot { 
struct kvm {

	struct mutex lock; /* protects the vcpus array and APIC accesses */

	spinlock_t mmu_lock;

	struct rw_semaphore slots_lock;

	struct mm_struct *mm; /* userspace tied to this vm */

	int nmemslots;

	struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS +