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    Subject[PATCH v3 kvm/queue 16/16] KVM: Register/unregister private memory slot to memfd
    Date
    Expose KVM_MEM_PRIVATE flag and register/unregister private memory
    slot to memfd when userspace sets the flag.

    KVM_MEM_PRIVATE is disallowed by default but architecture code can
    turn on it by implementing kvm_arch_private_memory_supported().

    Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
    Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
    ---
    include/linux/kvm_host.h | 1 +
    virt/kvm/kvm_main.c | 34 ++++++++++++++++++++++++++++++++--
    2 files changed, 33 insertions(+), 2 deletions(-)

    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index fabab3b77d57..5173c52e70d4 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -1229,6 +1229,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu);
    int kvm_arch_post_init_vm(struct kvm *kvm);
    void kvm_arch_pre_destroy_vm(struct kvm *kvm);
    int kvm_arch_create_vm_debugfs(struct kvm *kvm);
    +bool kvm_arch_private_memory_supported(struct kvm *kvm);

    #ifndef __KVM_HAVE_ARCH_VM_ALLOC
    /*
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index cf8dcb3b8c7f..1caebded52c4 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -1514,10 +1514,19 @@ static void kvm_replace_memslot(struct kvm *kvm,
    }
    }

    -static int check_memory_region_flags(const struct kvm_userspace_memory_region_ext *mem)
    +bool __weak kvm_arch_private_memory_supported(struct kvm *kvm)
    +{
    + return false;
    +}
    +
    +static int check_memory_region_flags(struct kvm *kvm,
    + const struct kvm_userspace_memory_region_ext *mem)
    {
    u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;

    + if (kvm_arch_private_memory_supported(kvm))
    + valid_flags |= KVM_MEM_PRIVATE;
    +
    #ifdef __KVM_HAVE_READONLY_MEM
    valid_flags |= KVM_MEM_READONLY;
    #endif
    @@ -1756,6 +1765,8 @@ static void kvm_delete_memslot(struct kvm *kvm,
    struct kvm_memory_slot *old,
    struct kvm_memory_slot *invalid_slot)
    {
    + if (old->flags & KVM_MEM_PRIVATE)
    + kvm_memfd_unregister(old);
    /*
    * Remove the old memslot (in the inactive memslots) by passing NULL as
    * the "new" slot, and for the invalid version in the active slots.
    @@ -1836,6 +1847,14 @@ static int kvm_set_memslot(struct kvm *kvm,
    kvm_invalidate_memslot(kvm, old, invalid_slot);
    }

    + if (new->flags & KVM_MEM_PRIVATE && change == KVM_MR_CREATE) {
    + r = kvm_memfd_register(kvm, new);
    + if (r) {
    + mutex_unlock(&kvm->slots_arch_lock);
    + return r;
    + }
    + }
    +
    r = kvm_prepare_memory_region(kvm, old, new, change);
    if (r) {
    /*
    @@ -1850,6 +1869,10 @@ static int kvm_set_memslot(struct kvm *kvm,
    } else {
    mutex_unlock(&kvm->slots_arch_lock);
    }
    +
    + if (new->flags & KVM_MEM_PRIVATE && change == KVM_MR_CREATE)
    + kvm_memfd_unregister(new);
    +
    return r;
    }

    @@ -1917,7 +1940,7 @@ 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;

    @@ -1974,6 +1997,10 @@ 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))
    @@ -2002,6 +2029,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
    new->npages = npages;
    new->flags = mem->flags;
    new->userspace_addr = mem->userspace_addr;
    + new->fd = mem->fd;
    + new->file = NULL;
    + new->ofs = mem->ofs;

    r = kvm_set_memslot(kvm, old, new, change);
    if (r)
    --
    2.17.1
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