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KVM: remove the usage of the mmap_sem for the protection of the memor…
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…y 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: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
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@avikivity
Izik Eidus authored and avikivity committed Mar 4, 2008
1 parent c7ac679 commit 72dc67a
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Showing 6 changed files with 75 additions and 40 deletions.
24 changes: 20 additions & 4 deletions arch/x86/kvm/mmu.c
View file
Expand Up @@ -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,
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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);
Expand Down
13 changes: 9 additions & 4 deletions arch/x86/kvm/paging_tmpl.h
View file
Expand Up @@ -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);
Expand Down Expand Up @@ -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.
*/
Expand All @@ -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);
Expand All @@ -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;
}
Expand Down
7 changes: 5 additions & 2 deletions arch/x86/kvm/vmx.c
View file
Expand Up @@ -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;
Expand All @@ -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;
}

Expand Down
65 changes: 37 additions & 28 deletions arch/x86/kvm/x86.c
View file
Expand Up @@ -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) {
Expand All @@ -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;
}
Expand All @@ -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;
}
Expand Down Expand Up @@ -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
Expand All @@ -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);

Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
Expand All @@ -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;

Expand Down Expand Up @@ -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)
Expand All @@ -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;
}

Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand All @@ -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)
Expand Down Expand Up @@ -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;
}

Expand All @@ -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);
Expand Down Expand Up @@ -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 ||
Expand All @@ -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

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -3234,20 +3239,24 @@ 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);
} else {
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: "
Expand Down

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