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    SubjectRe: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE
    Hi,

    On Fri, Dec 2, 2022 at 6:20 AM Chao Peng <chao.p.peng@linux.intel.com> wrote:
    >
    > Register/unregister private memslot to fd-based memory backing store
    > restrictedmem and implement the callbacks for restrictedmem_notifier:
    > - invalidate_start()/invalidate_end() to zap the existing memory
    > mappings in the KVM page table.
    > - error() to request KVM_REQ_MEMORY_MCE and later exit to userspace
    > with KVM_EXIT_SHUTDOWN.
    >
    > Expose KVM_MEM_PRIVATE for memslot and KVM_MEMORY_ATTRIBUTE_PRIVATE for
    > KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to userspace but either are
    > controlled by kvm_arch_has_private_mem() which should be rewritten by
    > architecture code.
    >
    > Co-developed-by: Yu Zhang <yu.c.zhang@linux.intel.com>
    > Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
    > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
    > Reviewed-by: Fuad Tabba <tabba@google.com>

    With the code to port it to pKVM/arm64:
    Tested-by: Fuad Tabba <tabba@google.com>

    Cheers,
    /fuad


    > ---
    > arch/x86/include/asm/kvm_host.h | 1 +
    > arch/x86/kvm/x86.c | 13 +++
    > include/linux/kvm_host.h | 3 +
    > virt/kvm/kvm_main.c | 179 +++++++++++++++++++++++++++++++-
    > 4 files changed, 191 insertions(+), 5 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > index 7772ab37ac89..27ef31133352 100644
    > --- a/arch/x86/include/asm/kvm_host.h
    > +++ b/arch/x86/include/asm/kvm_host.h
    > @@ -114,6 +114,7 @@
    > KVM_ARCH_REQ_FLAGS(31, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
    > #define KVM_REQ_HV_TLB_FLUSH \
    > KVM_ARCH_REQ_FLAGS(32, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
    > +#define KVM_REQ_MEMORY_MCE KVM_ARCH_REQ(33)
    >
    > #define CR0_RESERVED_BITS \
    > (~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
    > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > index 5aefcff614d2..c67e22f3e2ee 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -6587,6 +6587,13 @@ int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state)
    > }
    > #endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */
    >
    > +#ifdef CONFIG_HAVE_KVM_RESTRICTED_MEM
    > +void kvm_arch_memory_mce(struct kvm *kvm)
    > +{
    > + kvm_make_all_cpus_request(kvm, KVM_REQ_MEMORY_MCE);
    > +}
    > +#endif
    > +
    > static int kvm_vm_ioctl_get_clock(struct kvm *kvm, void __user *argp)
    > {
    > struct kvm_clock_data data = { 0 };
    > @@ -10357,6 +10364,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
    >
    > if (kvm_check_request(KVM_REQ_UPDATE_CPU_DIRTY_LOGGING, vcpu))
    > static_call(kvm_x86_update_cpu_dirty_logging)(vcpu);
    > +
    > + if (kvm_check_request(KVM_REQ_MEMORY_MCE, vcpu)) {
    > + vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
    > + r = 0;
    > + goto out;
    > + }
    > }
    >
    > if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||
    > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    > index 153842bb33df..f032d878e034 100644
    > --- a/include/linux/kvm_host.h
    > +++ b/include/linux/kvm_host.h
    > @@ -590,6 +590,7 @@ struct kvm_memory_slot {
    > struct file *restricted_file;
    > loff_t restricted_offset;
    > struct restrictedmem_notifier notifier;
    > + struct kvm *kvm;
    > };
    >
    > static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot)
    > @@ -2363,6 +2364,8 @@ static inline int kvm_restricted_mem_get_pfn(struct kvm_memory_slot *slot,
    > *pfn = page_to_pfn(page);
    > return ret;
    > }
    > +
    > +void kvm_arch_memory_mce(struct kvm *kvm);
    > #endif /* CONFIG_HAVE_KVM_RESTRICTED_MEM */
    >
    > #endif
    > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    > index e107afea32f0..ac835fc77273 100644
    > --- a/virt/kvm/kvm_main.c
    > +++ b/virt/kvm/kvm_main.c
    > @@ -936,6 +936,121 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
    >
    > #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
    >
    > +#ifdef CONFIG_HAVE_KVM_RESTRICTED_MEM
    > +static bool restrictedmem_range_is_valid(struct kvm_memory_slot *slot,
    > + pgoff_t start, pgoff_t end,
    > + gfn_t *gfn_start, gfn_t *gfn_end)
    > +{
    > + unsigned long base_pgoff = slot->restricted_offset >> PAGE_SHIFT;
    > +
    > + if (start > base_pgoff)
    > + *gfn_start = slot->base_gfn + start - base_pgoff;
    > + else
    > + *gfn_start = slot->base_gfn;
    > +
    > + if (end < base_pgoff + slot->npages)
    > + *gfn_end = slot->base_gfn + end - base_pgoff;
    > + else
    > + *gfn_end = slot->base_gfn + slot->npages;
    > +
    > + if (*gfn_start >= *gfn_end)
    > + return false;
    > +
    > + return true;
    > +}
    > +
    > +static void kvm_restrictedmem_invalidate_begin(struct restrictedmem_notifier *notifier,
    > + pgoff_t start, pgoff_t end)
    > +{
    > + struct kvm_memory_slot *slot = container_of(notifier,
    > + struct kvm_memory_slot,
    > + notifier);
    > + struct kvm *kvm = slot->kvm;
    > + gfn_t gfn_start, gfn_end;
    > + struct kvm_gfn_range gfn_range;
    > + int idx;
    > +
    > + if (!restrictedmem_range_is_valid(slot, start, end,
    > + &gfn_start, &gfn_end))
    > + return;
    > +
    > + gfn_range.start = gfn_start;
    > + gfn_range.end = gfn_end;
    > + gfn_range.slot = slot;
    > + gfn_range.pte = __pte(0);
    > + gfn_range.may_block = true;
    > +
    > + idx = srcu_read_lock(&kvm->srcu);
    > + KVM_MMU_LOCK(kvm);
    > +
    > + kvm_mmu_invalidate_begin(kvm);
    > + kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end);
    > + if (kvm_unmap_gfn_range(kvm, &gfn_range))
    > + kvm_flush_remote_tlbs(kvm);
    > +
    > + KVM_MMU_UNLOCK(kvm);
    > + srcu_read_unlock(&kvm->srcu, idx);
    > +}
    > +
    > +static void kvm_restrictedmem_invalidate_end(struct restrictedmem_notifier *notifier,
    > + pgoff_t start, pgoff_t end)
    > +{
    > + struct kvm_memory_slot *slot = container_of(notifier,
    > + struct kvm_memory_slot,
    > + notifier);
    > + struct kvm *kvm = slot->kvm;
    > + gfn_t gfn_start, gfn_end;
    > +
    > + if (!restrictedmem_range_is_valid(slot, start, end,
    > + &gfn_start, &gfn_end))
    > + return;
    > +
    > + KVM_MMU_LOCK(kvm);
    > + kvm_mmu_invalidate_end(kvm);
    > + KVM_MMU_UNLOCK(kvm);
    > +}
    > +
    > +static void kvm_restrictedmem_error(struct restrictedmem_notifier *notifier,
    > + pgoff_t start, pgoff_t end)
    > +{
    > + struct kvm_memory_slot *slot = container_of(notifier,
    > + struct kvm_memory_slot,
    > + notifier);
    > + kvm_arch_memory_mce(slot->kvm);
    > +}
    > +
    > +static struct restrictedmem_notifier_ops kvm_restrictedmem_notifier_ops = {
    > + .invalidate_start = kvm_restrictedmem_invalidate_begin,
    > + .invalidate_end = kvm_restrictedmem_invalidate_end,
    > + .error = kvm_restrictedmem_error,
    > +};
    > +
    > +static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
    > +{
    > + slot->notifier.ops = &kvm_restrictedmem_notifier_ops;
    > + restrictedmem_register_notifier(slot->restricted_file, &slot->notifier);
    > +}
    > +
    > +static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
    > +{
    > + restrictedmem_unregister_notifier(slot->restricted_file,
    > + &slot->notifier);
    > +}
    > +
    > +#else /* !CONFIG_HAVE_KVM_RESTRICTED_MEM */
    > +
    > +static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
    > +{
    > + WARN_ON_ONCE(1);
    > +}
    > +
    > +static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
    > +{
    > + WARN_ON_ONCE(1);
    > +}
    > +
    > +#endif /* CONFIG_HAVE_KVM_RESTRICTED_MEM */
    > +
    > #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
    > static int kvm_pm_notifier_call(struct notifier_block *bl,
    > unsigned long state,
    > @@ -980,6 +1095,11 @@ static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
    > /* This does not remove the slot from struct kvm_memslots data structures */
    > static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
    > {
    > + if (slot->flags & KVM_MEM_PRIVATE) {
    > + kvm_restrictedmem_unregister(slot);
    > + fput(slot->restricted_file);
    > + }
    > +
    > kvm_destroy_dirty_bitmap(slot);
    >
    > kvm_arch_free_memslot(kvm, slot);
    > @@ -1551,10 +1671,14 @@ static void kvm_replace_memslot(struct kvm *kvm,
    > }
    > }
    >
    > -static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
    > +static int check_memory_region_flags(struct kvm *kvm,
    > + const struct kvm_user_mem_region *mem)
    > {
    > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
    >
    > + if (kvm_arch_has_private_mem(kvm))
    > + valid_flags |= KVM_MEM_PRIVATE;
    > +
    > #ifdef __KVM_HAVE_READONLY_MEM
    > valid_flags |= KVM_MEM_READONLY;
    > #endif
    > @@ -1630,6 +1754,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
    > {
    > int r;
    >
    > + if (change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE)
    > + kvm_restrictedmem_register(new);
    > +
    > /*
    > * If dirty logging is disabled, nullify the bitmap; the old bitmap
    > * will be freed on "commit". If logging is enabled in both old and
    > @@ -1658,6 +1785,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
    > if (r && new && new->dirty_bitmap && (!old || !old->dirty_bitmap))
    > kvm_destroy_dirty_bitmap(new);
    >
    > + if (r && change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE)
    > + kvm_restrictedmem_unregister(new);
    > +
    > return r;
    > }
    >
    > @@ -1963,7 +2093,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
    > int as_id, id;
    > int r;
    >
    > - r = check_memory_region_flags(mem);
    > + r = check_memory_region_flags(kvm, mem);
    > if (r)
    > return r;
    >
    > @@ -1982,6 +2112,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
    > !access_ok((void __user *)(unsigned long)mem->userspace_addr,
    > mem->memory_size))
    > return -EINVAL;
    > + if (mem->flags & KVM_MEM_PRIVATE &&
    > + (mem->restricted_offset & (PAGE_SIZE - 1) ||
    > + mem->restricted_offset > U64_MAX - mem->memory_size))
    > + return -EINVAL;
    > if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
    > return -EINVAL;
    > if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
    > @@ -2020,6 +2154,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
    > if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages)
    > return -EINVAL;
    > } else { /* Modify an existing slot. */
    > + /* Private memslots are immutable, they can only be deleted. */
    > + if (mem->flags & KVM_MEM_PRIVATE)
    > + return -EINVAL;
    > if ((mem->userspace_addr != old->userspace_addr) ||
    > (npages != old->npages) ||
    > ((mem->flags ^ old->flags) & KVM_MEM_READONLY))
    > @@ -2048,10 +2185,28 @@ int __kvm_set_memory_region(struct kvm *kvm,
    > new->npages = npages;
    > new->flags = mem->flags;
    > new->userspace_addr = mem->userspace_addr;
    > + if (mem->flags & KVM_MEM_PRIVATE) {
    > + new->restricted_file = fget(mem->restricted_fd);
    > + if (!new->restricted_file ||
    > + !file_is_restrictedmem(new->restricted_file)) {
    > + r = -EINVAL;
    > + goto out;
    > + }
    > + new->restricted_offset = mem->restricted_offset;
    > + }
    > +
    > + new->kvm = kvm;
    >
    > r = kvm_set_memslot(kvm, old, new, change);
    > if (r)
    > - kfree(new);
    > + goto out;
    > +
    > + return 0;
    > +
    > +out:
    > + if (new->restricted_file)
    > + fput(new->restricted_file);
    > + kfree(new);
    > return r;
    > }
    > EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
    > @@ -2351,6 +2506,8 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
    > #ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES
    > static u64 kvm_supported_mem_attributes(struct kvm *kvm)
    > {
    > + if (kvm_arch_has_private_mem(kvm))
    > + return KVM_MEMORY_ATTRIBUTE_PRIVATE;
    > return 0;
    > }
    >
    > @@ -4822,16 +4979,28 @@ static long kvm_vm_ioctl(struct file *filp,
    > }
    > case KVM_SET_USER_MEMORY_REGION: {
    > struct kvm_user_mem_region mem;
    > - unsigned long size = sizeof(struct kvm_userspace_memory_region);
    > + unsigned int flags_offset = offsetof(typeof(mem), flags);
    > + unsigned long size;
    > + u32 flags;
    >
    > kvm_sanity_check_user_mem_region_alias();
    >
    > + memset(&mem, 0, sizeof(mem));
    > +
    > r = -EFAULT;
    > + if (get_user(flags, (u32 __user *)(argp + flags_offset)))
    > + goto out;
    > +
    > + if (flags & KVM_MEM_PRIVATE)
    > + size = sizeof(struct kvm_userspace_memory_region_ext);
    > + else
    > + size = sizeof(struct kvm_userspace_memory_region);
    > +
    > if (copy_from_user(&mem, argp, size))
    > goto out;
    >
    > r = -EINVAL;
    > - if (mem.flags & KVM_MEM_PRIVATE)
    > + if ((flags ^ mem.flags) & KVM_MEM_PRIVATE)
    > goto out;
    >
    > r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
    > --
    > 2.25.1
    >

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