[PATCH v11 17/43] KVM: arm64: nv: Support multiple nested Stage-2 mmu structures
Marc Zyngier
maz at kernel.org
Mon Nov 20 05:10:01 PST 2023
Add Stage-2 mmu data structures for virtual EL2 and for nested guests.
We don't yet populate shadow Stage-2 page tables, but we now have a
framework for getting to a shadow Stage-2 pgd.
We allocate twice the number of vcpus as Stage-2 mmu structures because
that's sufficient for each vcpu running two translation regimes without
having to flush the Stage-2 page tables.
Co-developed-by: Christoffer Dall <christoffer.dall at arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall at arm.com>
Signed-off-by: Marc Zyngier <maz at kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 41 ++++++
arch/arm64/include/asm/kvm_mmu.h | 9 ++
arch/arm64/include/asm/kvm_nested.h | 7 +
arch/arm64/kvm/arm.c | 12 ++
arch/arm64/kvm/mmu.c | 78 ++++++++---
arch/arm64/kvm/nested.c | 207 ++++++++++++++++++++++++++++
arch/arm64/kvm/reset.c | 6 +
7 files changed, 338 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f17fb7c42973..eb96fe9b686e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -188,8 +188,40 @@ struct kvm_s2_mmu {
uint64_t split_page_chunk_size;
struct kvm_arch *arch;
+
+ /*
+ * For a shadow stage-2 MMU, the virtual vttbr used by the
+ * host to parse the guest S2.
+ * This either contains:
+ * - the virtual VTTBR programmed by the guest hypervisor with
+ * CnP cleared
+ * - The value 1 (VMID=0, BADDR=0, CnP=1) if invalid
+ *
+ * We also cache the full VTCR which gets used for TLB invalidation,
+ * taking the ARM ARM's "Any of the bits in VTCR_EL2 are permitted
+ * to be cached in a TLB" to the letter.
+ */
+ u64 tlb_vttbr;
+ u64 tlb_vtcr;
+
+ /*
+ * true when this represents a nested context where virtual
+ * HCR_EL2.VM == 1
+ */
+ bool nested_stage2_enabled;
+
+ /*
+ * 0: Nobody is currently using this, check vttbr for validity
+ * >0: Somebody is actively using this.
+ */
+ atomic_t refcnt;
};
+static inline bool kvm_s2_mmu_valid(struct kvm_s2_mmu *mmu)
+{
+ return !(mmu->tlb_vttbr & 1);
+}
+
struct kvm_arch_memory_slot {
};
@@ -241,6 +273,14 @@ static inline u16 kvm_mpidr_index(struct kvm_mpidr_data *data, u64 mpidr)
struct kvm_arch {
struct kvm_s2_mmu mmu;
+ /*
+ * Stage 2 paging state for VMs with nested S2 using a virtual
+ * VMID.
+ */
+ struct kvm_s2_mmu *nested_mmus;
+ size_t nested_mmus_size;
+ int nested_mmus_next;
+
/* Interrupt controller */
struct vgic_dist vgic;
@@ -1186,6 +1226,7 @@ void kvm_vcpu_load_vhe(struct kvm_vcpu *vcpu);
void kvm_vcpu_put_vhe(struct kvm_vcpu *vcpu);
int __init kvm_set_ipa_limit(void);
+u32 kvm_get_pa_bits(struct kvm *kvm);
#define __KVM_HAVE_ARCH_VM_ALLOC
struct kvm *kvm_arch_alloc_vm(void);
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 49e0d4b36bd0..5c6fb2fb8287 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -119,6 +119,7 @@ alternative_cb_end
#include <asm/mmu_context.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_host.h>
+#include <asm/kvm_nested.h>
void kvm_update_va_mask(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst);
@@ -171,6 +172,7 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
int create_hyp_stack(phys_addr_t phys_addr, unsigned long *haddr);
void __init free_hyp_pgds(void);
+void kvm_unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size);
void stage2_unmap_vm(struct kvm *kvm);
int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long type);
void kvm_uninit_stage2_mmu(struct kvm *kvm);
@@ -339,5 +341,12 @@ static inline struct kvm *kvm_s2_mmu_to_kvm(struct kvm_s2_mmu *mmu)
{
return container_of(mmu->arch, struct kvm, arch);
}
+
+static inline u64 get_vmid(u64 vttbr)
+{
+ return (vttbr & VTTBR_VMID_MASK(kvm_get_vmid_bits())) >>
+ VTTBR_VMID_SHIFT;
+}
+
#endif /* __ASSEMBLY__ */
#endif /* __ARM64_KVM_MMU_H__ */
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index aa085f2f1947..f421ad294e68 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -60,6 +60,13 @@ static inline u64 translate_ttbr0_el2_to_ttbr0_el1(u64 ttbr0)
return ttbr0 & ~GENMASK_ULL(63, 48);
}
+extern void kvm_init_nested(struct kvm *kvm);
+extern int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu);
+extern void kvm_init_nested_s2_mmu(struct kvm_s2_mmu *mmu);
+extern struct kvm_s2_mmu *lookup_s2_mmu(struct kvm_vcpu *vcpu);
+extern void kvm_vcpu_load_hw_mmu(struct kvm_vcpu *vcpu);
+extern void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu);
+
extern bool forward_smc_trap(struct kvm_vcpu *vcpu);
extern bool __check_nv_sr_forward(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index b65df612b41b..2e76892c1a56 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -147,6 +147,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
mutex_unlock(&kvm->lock);
#endif
+ kvm_init_nested(kvm);
+
ret = kvm_share_hyp(kvm, kvm + 1);
if (ret)
return ret;
@@ -429,6 +431,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
struct kvm_s2_mmu *mmu;
int *last_ran;
+ if (vcpu_has_nv(vcpu))
+ kvm_vcpu_load_hw_mmu(vcpu);
+
mmu = vcpu->arch.hw_mmu;
last_ran = this_cpu_ptr(mmu->last_vcpu_ran);
@@ -479,9 +484,12 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
kvm_timer_vcpu_put(vcpu);
kvm_vgic_put(vcpu);
kvm_vcpu_pmu_restore_host(vcpu);
+ if (vcpu_has_nv(vcpu))
+ kvm_vcpu_put_hw_mmu(vcpu);
kvm_arm_vmid_clear_active();
vcpu_clear_on_unsupported_cpu(vcpu);
+
vcpu->cpu = -1;
}
@@ -1336,6 +1344,10 @@ static int kvm_setup_vcpu(struct kvm_vcpu *vcpu)
if (kvm_vcpu_has_pmu(vcpu) && !kvm->arch.arm_pmu)
ret = kvm_arm_set_default_pmu(kvm);
+ /* Prepare for nested if required */
+ if (!ret)
+ ret = kvm_vcpu_init_nested(vcpu);
+
return ret;
}
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index d87c8fcc4c24..588ce46c0ad0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -305,7 +305,7 @@ static void invalidate_icache_guest_page(void *va, size_t size)
* does.
*/
/**
- * unmap_stage2_range -- Clear stage2 page table entries to unmap a range
+ * __unmap_stage2_range -- Clear stage2 page table entries to unmap a range
* @mmu: The KVM stage-2 MMU pointer
* @start: The intermediate physical base address of the range to unmap
* @size: The size of the area to unmap
@@ -328,7 +328,7 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64
may_block));
}
-static void unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size)
+void kvm_unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size)
{
__unmap_stage2_range(mmu, start, size, true);
}
@@ -853,21 +853,9 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
.icache_inval_pou = invalidate_icache_guest_page,
};
-/**
- * kvm_init_stage2_mmu - Initialise a S2 MMU structure
- * @kvm: The pointer to the KVM structure
- * @mmu: The pointer to the s2 MMU structure
- * @type: The machine type of the virtual machine
- *
- * Allocates only the stage-2 HW PGD level table(s).
- * Note we don't need locking here as this is only called when the VM is
- * created, which can only be done once.
- */
-int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long type)
+static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
{
u32 kvm_ipa_limit = get_kvm_ipa_limit();
- int cpu, err;
- struct kvm_pgtable *pgt;
u64 mmfr0, mmfr1;
u32 phys_shift;
@@ -894,11 +882,58 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
mmu->vtcr = kvm_get_vtcr(mmfr0, mmfr1, phys_shift);
+ return 0;
+}
+
+/**
+ * kvm_init_stage2_mmu - Initialise a S2 MMU structure
+ * @kvm: The pointer to the KVM structure
+ * @mmu: The pointer to the s2 MMU structure
+ * @type: The machine type of the virtual machine
+ *
+ * Allocates only the stage-2 HW PGD level table(s).
+ * Note we don't need locking here as this is only called in two cases:
+ *
+ * - when the VM is created, which can't race against anything
+ *
+ * - when secondary kvm_s2_mmu structures are initialised for NV
+ * guests, and the caller must hold kvm->lock as this is called on a
+ * per-vcpu basis.
+ */
+int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long type)
+{
+ int cpu, err;
+ struct kvm_pgtable *pgt;
+
+ /*
+ * If we already have our page tables in place, and that the
+ * MMU context is the canonical one, we have a bug somewhere,
+ * as this is only supposed to ever happen once per VM.
+ *
+ * Otherwise, we're building nested page tables, and that's
+ * probably because userspace called KVM_ARM_VCPU_INIT more
+ * than once on the same vcpu. Since that's actually legal,
+ * don't kick a fuss and leave gracefully.
+ */
if (mmu->pgt != NULL) {
+ if (&kvm->arch.mmu != mmu)
+ return 0;
+
kvm_err("kvm_arch already initialized?\n");
return -EINVAL;
}
+ /*
+ * We only initialise the IPA range on the canonical MMU, so
+ * the type is meaningless in all other situations.
+ */
+ if (&kvm->arch.mmu != mmu)
+ type = kvm_get_pa_bits(kvm);
+
+ err = kvm_init_ipa_range(mmu, type);
+ if (err)
+ return err;
+
pgt = kzalloc(sizeof(*pgt), GFP_KERNEL_ACCOUNT);
if (!pgt)
return -ENOMEM;
@@ -923,6 +958,10 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
mmu->pgt = pgt;
mmu->pgd_phys = __pa(pgt->pgd);
+
+ if (&kvm->arch.mmu != mmu)
+ kvm_init_nested_s2_mmu(mmu);
+
return 0;
out_destroy_pgtable:
@@ -974,7 +1013,7 @@ static void stage2_unmap_memslot(struct kvm *kvm,
if (!(vma->vm_flags & VM_PFNMAP)) {
gpa_t gpa = addr + (vm_start - memslot->userspace_addr);
- unmap_stage2_range(&kvm->arch.mmu, gpa, vm_end - vm_start);
+ kvm_unmap_stage2_range(&kvm->arch.mmu, gpa, vm_end - vm_start);
}
hva = vm_end;
} while (hva < reg_end);
@@ -2054,11 +2093,6 @@ void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
{
}
-void kvm_arch_flush_shadow_all(struct kvm *kvm)
-{
- kvm_uninit_stage2_mmu(kvm);
-}
-
void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
@@ -2066,7 +2100,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
phys_addr_t size = slot->npages << PAGE_SHIFT;
write_lock(&kvm->mmu_lock);
- unmap_stage2_range(&kvm->arch.mmu, gpa, size);
+ kvm_unmap_stage2_range(&kvm->arch.mmu, gpa, size);
write_unlock(&kvm->mmu_lock);
}
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 66d05f5d39a2..c5752ab8c3fe 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -7,7 +7,9 @@
#include <linux/kvm.h>
#include <linux/kvm_host.h>
+#include <asm/kvm_arm.h>
#include <asm/kvm_emulate.h>
+#include <asm/kvm_mmu.h>
#include <asm/kvm_nested.h>
#include <asm/sysreg.h>
@@ -16,6 +18,211 @@
/* Protection against the sysreg repainting madness... */
#define NV_FTR(r, f) ID_AA64##r##_EL1_##f
+void kvm_init_nested(struct kvm *kvm)
+{
+ kvm->arch.nested_mmus = NULL;
+ kvm->arch.nested_mmus_size = 0;
+}
+
+int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_s2_mmu *tmp;
+ int num_mmus;
+ int ret = -ENOMEM;
+
+ if (!test_bit(KVM_ARM_VCPU_HAS_EL2, vcpu->kvm->arch.vcpu_features))
+ return 0;
+
+ if (!cpus_have_final_cap(ARM64_HAS_NESTED_VIRT))
+ return -EINVAL;
+
+ /*
+ * Let's treat memory allocation failures as benign: If we fail to
+ * allocate anything, return an error and keep the allocated array
+ * alive. Userspace may try to recover by intializing the vcpu
+ * again, and there is no reason to affect the whole VM for this.
+ */
+ num_mmus = atomic_read(&kvm->online_vcpus) * 2;
+ tmp = krealloc(kvm->arch.nested_mmus,
+ num_mmus * sizeof(*kvm->arch.nested_mmus),
+ GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+ if (tmp) {
+ /*
+ * If we went through a realocation, adjust the MMU
+ * back-pointers in the previously initialised
+ * pg_table structures.
+ */
+ if (kvm->arch.nested_mmus != tmp) {
+ int i;
+
+ for (i = 0; i < num_mmus - 2; i++)
+ tmp[i].pgt->mmu = &tmp[i];
+ }
+
+ if (kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 1], 0) ||
+ kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 2], 0)) {
+ kvm_free_stage2_pgd(&tmp[num_mmus - 1]);
+ kvm_free_stage2_pgd(&tmp[num_mmus - 2]);
+ } else {
+ kvm->arch.nested_mmus_size = num_mmus;
+ ret = 0;
+ }
+
+ kvm->arch.nested_mmus = tmp;
+ }
+
+ return ret;
+}
+
+/* Must be called with kvm->mmu_lock held */
+struct kvm_s2_mmu *lookup_s2_mmu(struct kvm_vcpu *vcpu)
+{
+ bool nested_stage2_enabled;
+ u64 vttbr, vtcr, hcr;
+ struct kvm *kvm;
+ int i;
+
+ kvm = vcpu->kvm;
+
+ vttbr = vcpu_read_sys_reg(vcpu, VTTBR_EL2);
+ vtcr = vcpu_read_sys_reg(vcpu, VTCR_EL2);
+ hcr = vcpu_read_sys_reg(vcpu, HCR_EL2);
+
+ nested_stage2_enabled = hcr & HCR_VM;
+
+ /* Don't consider the CnP bit for the vttbr match */
+ vttbr = vttbr & ~VTTBR_CNP_BIT;
+
+ /*
+ * Two possibilities when looking up a S2 MMU context:
+ *
+ * - either S2 is enabled in the guest, and we need a context that is
+ * S2-enabled and matches the full VTTBR (VMID+BADDR) and VTCR,
+ * which makes it safe from a TLB conflict perspective (a broken
+ * guest won't be able to generate them),
+ *
+ * - or S2 is disabled, and we need a context that is S2-disabled
+ * and matches the VMID only, as all TLBs are tagged by VMID even
+ * if S2 translation is disabled.
+ */
+ for (i = 0; i < kvm->arch.nested_mmus_size; i++) {
+ struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i];
+
+ if (!kvm_s2_mmu_valid(mmu))
+ continue;
+
+ if (nested_stage2_enabled &&
+ mmu->nested_stage2_enabled &&
+ vttbr == mmu->tlb_vttbr &&
+ vtcr == mmu->tlb_vtcr)
+ return mmu;
+
+ if (!nested_stage2_enabled &&
+ !mmu->nested_stage2_enabled &&
+ get_vmid(vttbr) == get_vmid(mmu->tlb_vttbr))
+ return mmu;
+ }
+ return NULL;
+}
+
+/* Must be called with kvm->mmu_lock held */
+static struct kvm_s2_mmu *get_s2_mmu_nested(struct kvm_vcpu *vcpu)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_s2_mmu *s2_mmu;
+ int i;
+
+ s2_mmu = lookup_s2_mmu(vcpu);
+ if (s2_mmu)
+ goto out;
+
+ /*
+ * Make sure we don't always search from the same point, or we
+ * will always reuse a potentially active context, leaving
+ * free contexts unused.
+ */
+ for (i = kvm->arch.nested_mmus_next;
+ i < (kvm->arch.nested_mmus_size + kvm->arch.nested_mmus_next);
+ i++) {
+ s2_mmu = &kvm->arch.nested_mmus[i % kvm->arch.nested_mmus_size];
+
+ if (atomic_read(&s2_mmu->refcnt) == 0)
+ break;
+ }
+ BUG_ON(atomic_read(&s2_mmu->refcnt)); /* We have struct MMUs to spare */
+
+ /* Set the scene for the next search */
+ kvm->arch.nested_mmus_next = (i + 1) % kvm->arch.nested_mmus_size;
+
+ if (kvm_s2_mmu_valid(s2_mmu)) {
+ /* Clear the old state */
+ kvm_unmap_stage2_range(s2_mmu, 0, kvm_phys_size(s2_mmu));
+ if (atomic64_read(&s2_mmu->vmid.id))
+ kvm_call_hyp(__kvm_tlb_flush_vmid, s2_mmu);
+ }
+
+ /*
+ * The virtual VMID (modulo CnP) will be used as a key when matching
+ * an existing kvm_s2_mmu.
+ *
+ * We cache VTCR at allocation time, once and for all. It'd be great
+ * if the guest didn't screw that one up, as this is not very
+ * forgiving...
+ */
+ s2_mmu->tlb_vttbr = vcpu_read_sys_reg(vcpu, VTTBR_EL2) & ~VTTBR_CNP_BIT;
+ s2_mmu->tlb_vtcr = vcpu_read_sys_reg(vcpu, VTCR_EL2);
+ s2_mmu->nested_stage2_enabled = vcpu_read_sys_reg(vcpu, HCR_EL2) & HCR_VM;
+
+out:
+ atomic_inc(&s2_mmu->refcnt);
+ return s2_mmu;
+}
+
+void kvm_init_nested_s2_mmu(struct kvm_s2_mmu *mmu)
+{
+ mmu->tlb_vttbr = 1;
+ mmu->nested_stage2_enabled = false;
+ atomic_set(&mmu->refcnt, 0);
+}
+
+void kvm_vcpu_load_hw_mmu(struct kvm_vcpu *vcpu)
+{
+ if (is_hyp_ctxt(vcpu)) {
+ vcpu->arch.hw_mmu = &vcpu->kvm->arch.mmu;
+ } else {
+ write_lock(&vcpu->kvm->mmu_lock);
+ vcpu->arch.hw_mmu = get_s2_mmu_nested(vcpu);
+ write_unlock(&vcpu->kvm->mmu_lock);
+ }
+}
+
+void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu)
+{
+ if (vcpu->arch.hw_mmu != &vcpu->kvm->arch.mmu) {
+ atomic_dec(&vcpu->arch.hw_mmu->refcnt);
+ vcpu->arch.hw_mmu = NULL;
+ }
+}
+
+void kvm_arch_flush_shadow_all(struct kvm *kvm)
+{
+ int i;
+
+ for (i = 0; i < kvm->arch.nested_mmus_size; i++) {
+ struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i];
+
+ WARN_ON(atomic_read(&mmu->refcnt));
+
+ if (!atomic_read(&mmu->refcnt))
+ kvm_free_stage2_pgd(mmu);
+ }
+ kfree(kvm->arch.nested_mmus);
+ kvm->arch.nested_mmus = NULL;
+ kvm->arch.nested_mmus_size = 0;
+ kvm_uninit_stage2_mmu(kvm);
+}
+
/*
* Our emulated CPU doesn't support all the possible features. For the
* sake of simplicity (and probably mental sanity), wipe out a number
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 5bb4de162cab..e106ea01598f 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -266,6 +266,12 @@ void kvm_reset_vcpu(struct kvm_vcpu *vcpu)
preempt_enable();
}
+u32 kvm_get_pa_bits(struct kvm *kvm)
+{
+ /* Fixed limit until we can configure ID_AA64MMFR0.PARange */
+ return kvm_ipa_limit;
+}
+
u32 get_kvm_ipa_limit(void)
{
return kvm_ipa_limit;
--
2.39.2
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