[PATCH 37/59] KVM: arm64: nv: Handle shadow stage 2 page faults

Marc Zyngier
2019-06-21T09:40:21Z

From: Christoffer Dall <christoffer.dall@linaro.org>

If we are faulting on a shadow stage 2 translation, we first walk the
guest hypervisor's stage 2 page table to see if it has a mapping. If
not, we inject a stage 2 page fault to the virtual EL2. Otherwise, we
create a mapping in the shadow stage 2 page table.

Note that we have to deal with two IPAs when we got a showdow stage 2
page fault. One is the address we faulted on, and is in the L2 guest
phys space. The other is from the guest stage-2 page table walk, and is
in the L1 guest phys space. To differentiate them, we rename variable
names so that fault_ipa is used for the former and ipa is used for the
latter.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm/include/asm/kvm_mmu.h | 52 +++++++++++++++
arch/arm64/include/asm/kvm_emulate.h | 6 ++
arch/arm64/include/asm/kvm_nested.h | 20 +++++-
arch/arm64/kvm/nested.c | 41 ++++++++++++
virt/kvm/arm/mmio.c | 12 ++--
virt/kvm/arm/mmu.c | 99 ++++++++++++++++++++++------
6 files changed, 203 insertions(+), 27 deletions(-)

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index e6984b6da2ce..afabf1fd1d17 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -423,6 +423,58 @@ static inline void kvm_set_ipa_limit(void) {}
static inline void kvm_init_s2_mmu(struct kvm_s2_mmu *mmu) {}
static inline void kvm_init_nested(struct kvm *kvm) {}

+struct kvm_s2_trans {};
+static inline phys_addr_t kvm_s2_trans_output(struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline unsigned long kvm_s2_trans_size(struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline u32 kvm_s2_trans_esr(struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t ipa,
+ struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu,
+ struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline void kvm_inject_s2_fault(struct kvm_vcpu *vcpu, u32 esr)
+{
+ BUG();
+}
+
+static inline bool kvm_s2_trans_readable(struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline bool kvm_s2_trans_writable(struct kvm_s2_trans *trans)
+{
+ BUG();
+}
+
+static inline void kvm_nested_s2_flush(struct kvm *kvm) {}
+static inline void kvm_nested_s2_wp(struct kvm *kvm) {}
+static inline void kvm_nested_s2_clear(struct kvm *kvm) {}
+
+static inline bool kvm_is_shadow_s2_fault(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+
static __always_inline u64 kvm_get_vttbr(struct kvm_s2_mmu *mmu)
{
struct kvm_vmid *vmid = &mmu->vmid;
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 73d8c54a52c6..b49a47f3daa8 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -606,4 +606,10 @@ static inline void __hyp_text __kvm_skip_instr(struct kvm_vcpu *vcpu)
write_sysreg_el2(*vcpu_pc(vcpu), SYS_ELR);
}

+static inline bool kvm_is_shadow_s2_fault(struct kvm_vcpu *vcpu)
+{
+ return (vcpu->arch.hw_mmu != &vcpu->kvm->arch.mmu &&
+ vcpu->arch.hw_mmu->nested_stage2_enabled);
+}
+
#endif /* __ARM64_KVM_EMULATE_H__ */
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 686ba53379ab..052d46d96201 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -19,7 +19,7 @@ extern void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu);

struct kvm_s2_trans {
phys_addr_t output;
- phys_addr_t block_size;
+ unsigned long block_size;
bool writable;
bool readable;
int level;
@@ -27,9 +27,27 @@ struct kvm_s2_trans {
u64 upper_attr;
};

+static inline phys_addr_t kvm_s2_trans_output(struct kvm_s2_trans *trans)
+{
+ return trans->output;
+}
+
+static inline unsigned long kvm_s2_trans_size(struct kvm_s2_trans *trans)
+{
+ return trans->block_size;
+}
+
+static inline u32 kvm_s2_trans_esr(struct kvm_s2_trans *trans)
+{
+ return trans->esr;
+}
+
extern int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
struct kvm_s2_trans *result);

+extern int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu,
+ struct kvm_s2_trans *trans);
+extern int kvm_inject_s2_fault(struct kvm_vcpu *vcpu, u64 esr_el2);
int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe);
extern bool forward_traps(struct kvm_vcpu *vcpu, u64 control_bit);
extern bool forward_nv_traps(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 6a9bd68b769b..023027fa2db5 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -300,6 +300,8 @@ int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
u64 vtcr = vcpu_read_sys_reg(vcpu, VTCR_EL2);
struct s2_walk_info wi;

+ result->esr = 0;
+
if (!nested_virt_in_use(vcpu))
return 0;

@@ -415,6 +417,45 @@ void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu)
}
}

+/*
+ * Returns non-zero if permission fault is handled by injecting it to the next
+ * level hypervisor.
+ */
+int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu, struct kvm_s2_trans *trans)
+{
+ unsigned long fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
+ bool forward_fault = false;
+
+ trans->esr = 0;
+
+ if (fault_status != FSC_PERM)
+ return 0;
+
+ if (kvm_vcpu_trap_is_iabt(vcpu)) {
+ forward_fault = (trans->upper_attr & PTE_S2_XN);
+ } else {
+ bool write_fault = kvm_is_write_fault(vcpu);
+
+ forward_fault = ((write_fault && !trans->writable) ||
+ (!write_fault && !trans->readable));
+ }
+
+ if (forward_fault) {
+ trans->esr = esr_s2_fault(vcpu, trans->level, ESR_ELx_FSC_PERM);
+ return 1;
+ }
+
+ return 0;
+}
+
+int kvm_inject_s2_fault(struct kvm_vcpu *vcpu, u64 esr_el2)
+{
+ vcpu_write_sys_reg(vcpu, vcpu->arch.fault.far_el2, FAR_EL2);
+ vcpu_write_sys_reg(vcpu, vcpu->arch.fault.hpfar_el2, HPFAR_EL2);
+
+ return kvm_inject_nested_sync(vcpu, esr_el2);
+}
+
/*
* Inject wfx to the virtual EL2 if this is not from the virtual EL2 and
* the virtual HCR_EL2.TWX is set. Otherwise, let the host hypervisor
diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c
index a8a6a0c883f1..2b5de8388bf4 100644
--- a/virt/kvm/arm/mmio.c
+++ b/virt/kvm/arm/mmio.c
@@ -142,7 +142,7 @@ static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len)
}

int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
- phys_addr_t fault_ipa)
+ phys_addr_t ipa)
{
unsigned long data;
unsigned long rt;
@@ -171,22 +171,22 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
len);

- trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, &data);
+ trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, ipa, &data);
kvm_mmio_write_buf(data_buf, len, data);

- ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len,
+ ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, ipa, len,
data_buf);
} else {
trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len,
- fault_ipa, NULL);
+ ipa, NULL);

- ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len,
+ ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, ipa, len,
data_buf);
}

/* Now prepare kvm_run for the potential return to userland. */
run->mmio.is_write = is_write;
- run->mmio.phys_addr = fault_ipa;
+ run->mmio.phys_addr = ipa;
run->mmio.len = len;

if (!ret) {
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index faa61a81c8cc..3c7845832db8 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1384,7 +1384,8 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
return ret;
}

-static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
+static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap,
+ phys_addr_t *fault_ipap)
{
kvm_pfn_t pfn = *pfnp;
gfn_t gfn = *ipap >> PAGE_SHIFT;
@@ -1418,6 +1419,7 @@ static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
mask = PTRS_PER_PMD - 1;
VM_BUG_ON((gfn & mask) != (pfn & mask));
if (pfn & mask) {
+ *fault_ipap &= PMD_MASK;
*ipap &= PMD_MASK;
kvm_release_pfn_clean(pfn);
pfn &= ~mask;
@@ -1681,14 +1683,16 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
}

static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
- struct kvm_memory_slot *memslot, unsigned long hva,
- unsigned long fault_status)
+ struct kvm_s2_trans *nested,
+ struct kvm_memory_slot *memslot,
+ unsigned long hva, unsigned long fault_status)
{
int ret;
- bool write_fault, writable, force_pte = false;
+ bool write_fault, writable;
bool exec_fault, needs_exec;
unsigned long mmu_seq;
- gfn_t gfn = fault_ipa >> PAGE_SHIFT;
+ phys_addr_t ipa = fault_ipa;
+ gfn_t gfn;
struct kvm *kvm = vcpu->kvm;
struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
struct vm_area_struct *vma;
@@ -1697,6 +1701,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
bool logging_active = memslot_is_logging(memslot);
unsigned long vma_pagesize, flags = 0;
struct kvm_s2_mmu *mmu = vcpu->arch.hw_mmu;
+ unsigned long max_map_size = PUD_SIZE;

write_fault = kvm_is_write_fault(vcpu);
exec_fault = kvm_vcpu_trap_is_iabt(vcpu);
@@ -1717,11 +1722,26 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
}

vma_pagesize = vma_kernel_pagesize(vma);
- if (logging_active ||
- !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
- force_pte = true;
- vma_pagesize = PAGE_SIZE;
+
+ if (!fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize))
+ max_map_size = PAGE_SIZE;
+
+ if (logging_active)
+ max_map_size = PAGE_SIZE;
+
+ if (kvm_is_shadow_s2_fault(vcpu)) {
+ ipa = kvm_s2_trans_output(nested);
+
+ /*
+ * If we're about to create a shadow stage 2 entry, then we
+ * can only create a block mapping if the guest stage 2 page
+ * table uses at least as big a mapping.
+ */
+ max_map_size = min(kvm_s2_trans_size(nested), max_map_size);
}
+ gfn = ipa >> PAGE_SHIFT;
+
+ vma_pagesize = min(vma_pagesize, max_map_size);

/*
* The stage2 has a minimum of 2 level table (For arm64 see
@@ -1731,8 +1751,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* 3 levels, i.e, PMD is not folded.
*/
if (vma_pagesize == PMD_SIZE ||
- (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm)))
- gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
+ (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm))) {
+ gfn = (ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
+ }
up_read(&current->mm->mmap_sem);

/* We need minimum second+third level pages */
@@ -1784,7 +1805,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;

- if (vma_pagesize == PAGE_SIZE && !force_pte) {
+ if (vma_pagesize == PAGE_SIZE && max_map_size >= PMD_SIZE) {
/*
* Only PMD_SIZE transparent hugepages(THP) are
* currently supported. This code will need to be
@@ -1794,7 +1815,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* aligned and that the block is contained within the memslot.
*/
if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) &&
- transparent_hugepage_adjust(&pfn, &fault_ipa))
+ transparent_hugepage_adjust(&pfn, &ipa, &fault_ipa))
vma_pagesize = PMD_SIZE;
}

@@ -1919,8 +1940,10 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
unsigned long fault_status;
- phys_addr_t fault_ipa;
+ phys_addr_t fault_ipa; /* The address we faulted on */
+ phys_addr_t ipa; /* Always the IPA in the L1 guest phys space */
struct kvm_memory_slot *memslot;
+ struct kvm_s2_trans nested_trans;
unsigned long hva;
bool is_iabt, write_fault, writable;
gfn_t gfn;
@@ -1928,7 +1951,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)

fault_status = kvm_vcpu_trap_get_fault_type(vcpu);

- fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
+ ipa = fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
is_iabt = kvm_vcpu_trap_is_iabt(vcpu);

/* Synchronous External Abort? */
@@ -1952,6 +1975,12 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
/* Check the stage-2 fault is trans. fault or write fault */
if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
fault_status != FSC_ACCESS) {
+ /*
+ * We must never see an address size fault on shadow stage 2
+ * page table walk, because we would have injected an addr
+ * size fault when we walked the nested s2 page and not
+ * create the shadow entry.
+ */
kvm_err("Unsupported FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",
kvm_vcpu_trap_get_class(vcpu),
(unsigned long)kvm_vcpu_trap_get_fault(vcpu),
@@ -1961,7 +1990,36 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)

idx = srcu_read_lock(&vcpu->kvm->srcu);

- gfn = fault_ipa >> PAGE_SHIFT;
+ /*
+ * We may have faulted on a shadow stage 2 page table if we are
+ * running a nested guest. In this case, we have to resolve the L2
+ * IPA to the L1 IPA first, before knowing what kind of memory should
+ * back the L1 IPA.
+ *
+ * If the shadow stage 2 page table walk faults, then we simply inject
+ * this to the guest and carry on.
+ */
+ if (kvm_is_shadow_s2_fault(vcpu)) {
+ u32 esr;
+
+ ret = kvm_walk_nested_s2(vcpu, fault_ipa, &nested_trans);
+ esr = kvm_s2_trans_esr(&nested_trans);
+ if (esr)
+ kvm_inject_s2_fault(vcpu, esr);
+ if (ret)
+ goto out_unlock;
+
+ ret = kvm_s2_handle_perm_fault(vcpu, &nested_trans);
+ esr = kvm_s2_trans_esr(&nested_trans);
+ if (esr)
+ kvm_inject_s2_fault(vcpu, esr);
+ if (ret)
+ goto out_unlock;
+
+ ipa = kvm_s2_trans_output(&nested_trans);
+ }
+
+ gfn = ipa >> PAGE_SHIFT;
memslot = gfn_to_memslot(vcpu->kvm, gfn);
hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
write_fault = kvm_is_write_fault(vcpu);
@@ -1995,13 +2053,13 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
* faulting VA. This is always 12 bits, irrespective
* of the page size.
*/
- fault_ipa |= kvm_vcpu_get_hfar(vcpu) & ((1 << 12) - 1);
- ret = io_mem_abort(vcpu, run, fault_ipa);
+ ipa |= kvm_vcpu_get_hfar(vcpu) & ((1 << 12) - 1);
+ ret = io_mem_abort(vcpu, run, ipa);
goto out_unlock;
}

/* Userspace should not be able to register out-of-bounds IPAs */
- VM_BUG_ON(fault_ipa >= kvm_phys_size(vcpu->kvm));
+ VM_BUG_ON(ipa >= kvm_phys_size(vcpu->kvm));

if (fault_status == FSC_ACCESS) {
handle_access_fault(vcpu, fault_ipa);
@@ -2009,7 +2067,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
goto out_unlock;
}

- ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);
+ ret = user_mem_abort(vcpu, fault_ipa, &nested_trans,
+ memslot, hva, fault_status);
if (ret == 0)
ret = 1;
out_unlock:
--
2.20.1