Re: [PATCH v8 11/18] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl

From: Steve Rutherford
Date: Fri May 29 2020 - 22:07:24 EST

On Tue, May 5, 2020 at 2:18 PM Ashish Kalra <Ashish.Kalra@xxxxxxx> wrote:
>
> From: Brijesh Singh <Brijesh.Singh@xxxxxxx>
>
> The ioctl can be used to set page encryption bitmap for an
> incoming guest.
>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>
> Cc: Joerg Roedel <joro@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Reviewed-by: Venu Busireddy <venu.busireddy@xxxxxxxxxx>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> ---
> Documentation/virt/kvm/api.rst | 44 +++++++++++++++++++++++++++++
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/svm/sev.c | 50 +++++++++++++++++++++++++++++++++
> arch/x86/kvm/svm/svm.c | 1 +
> arch/x86/kvm/svm/svm.h | 1 +
> arch/x86/kvm/x86.c | 12 ++++++++
> include/uapi/linux/kvm.h | 1 +
> 7 files changed, 111 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index ecad84086892..fa70017ee693 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4663,6 +4663,28 @@ or shared. The bitmap can be used during the guest migration. If the page
> is private then the userspace need to use SEV migration commands to transmit
> the page.
>
> +4.126 KVM_SET_PAGE_ENC_BITMAP (vm ioctl)
> +---------------------------------------
> +
> +:Capability: basic
> +:Architectures: x86
> +:Type: vm ioctl
> +:Parameters: struct kvm_page_enc_bitmap (in/out)
> +:Returns: 0 on success, -1 on error
> +
> +/* for KVM_SET_PAGE_ENC_BITMAP */
> +struct kvm_page_enc_bitmap {
> + __u64 start_gfn;
> + __u64 num_pages;
> + union {
> + void __user *enc_bitmap; /* one bit per page */
> + __u64 padding2;
> + };
> +};
> +
> +During the guest live migration the outgoing guest exports its page encryption
> +bitmap, the KVM_SET_PAGE_ENC_BITMAP can be used to build the page encryption
> +bitmap for an incoming guest.
>
> 4.125 KVM_S390_PV_COMMAND
> -------------------------
> @@ -4717,6 +4739,28 @@ KVM_PV_VM_VERIFY
> Verify the integrity of the unpacked image. Only if this succeeds,
> KVM is allowed to start protected VCPUs.
>
> +4.126 KVM_SET_PAGE_ENC_BITMAP (vm ioctl)
> +---------------------------------------
> +
> +:Capability: basic
> +:Architectures: x86
> +:Type: vm ioctl
> +:Parameters: struct kvm_page_enc_bitmap (in/out)
> +:Returns: 0 on success, -1 on error
> +
> +/* for KVM_SET_PAGE_ENC_BITMAP */
> +struct kvm_page_enc_bitmap {
> + __u64 start_gfn;
> + __u64 num_pages;
> + union {
> + void __user *enc_bitmap; /* one bit per page */
> + __u64 padding2;
> + };
> +};
> +
> +During the guest live migration the outgoing guest exports its page encryption
> +bitmap, the KVM_SET_PAGE_ENC_BITMAP can be used to build the page encryption
> +bitmap for an incoming guest.
>
> 5. The kvm_run structure
> ========================
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9e428befb6a4..fc74144d5ab0 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1258,6 +1258,8 @@ struct kvm_x86_ops {
> unsigned long sz, unsigned long mode);
> int (*get_page_enc_bitmap)(struct kvm *kvm,
> struct kvm_page_enc_bitmap *bmap);
> + int (*set_page_enc_bitmap)(struct kvm *kvm,
> + struct kvm_page_enc_bitmap *bmap);
> };
>
> struct kvm_x86_init_ops {
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 387045902470..30efc1068707 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1504,6 +1504,56 @@ int svm_get_page_enc_bitmap(struct kvm *kvm,
> return ret;
> }
>
> +int svm_set_page_enc_bitmap(struct kvm *kvm,
> + struct kvm_page_enc_bitmap *bmap)
> +{
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> + unsigned long gfn_start, gfn_end;
> + unsigned long *bitmap;
> + unsigned long sz;
> + int ret;
> +
> + if (!sev_guest(kvm))
> + return -ENOTTY;
> + /* special case of resetting the complete bitmap */
> + if (!bmap->enc_bitmap) {
> + mutex_lock(&kvm->lock);
> + /* by default all pages are marked encrypted */
> + if (sev->page_enc_bmap_size)
> + bitmap_fill(sev->page_enc_bmap,
> + sev->page_enc_bmap_size);
> + mutex_unlock(&kvm->lock);
> + return 0;
> + }
>
> +
> + gfn_start = bmap->start_gfn;
> + gfn_end = gfn_start + bmap->num_pages;
> +
> + sz = ALIGN(bmap->num_pages, BITS_PER_LONG) / 8;
> + bitmap = kmalloc(sz, GFP_KERNEL);
> + if (!bitmap)
> + return -ENOMEM;
> +
> + ret = -EFAULT;
> + if (copy_from_user(bitmap, bmap->enc_bitmap, sz))
> + goto out;
> +
> + mutex_lock(&kvm->lock);
> + ret = sev_resize_page_enc_bitmap(kvm, gfn_end);
> + if (ret)
> + goto unlock;
> +
> + bitmap_copy(sev->page_enc_bmap + BIT_WORD(gfn_start), bitmap,
> + (gfn_end - gfn_start));

I *think* this assumes that gfn_start is a multiple of 8. I'm not
certain I have a clean suggestion for fixing this, other than
advertising that this is an expectation, and returning an error if
that is not true.

If I'm reading bitmap_copy correctly, I also think it assumes all
bitmaps have lengths that are unsigned long aligned, which surprised
me.
>
> +
> + ret = 0;
> +unlock:
> + mutex_unlock(&kvm->lock);
> +out:
> + kfree(bitmap);
> + return ret;
> +}
> +
> int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> {
> struct kvm_sev_cmd sev_cmd;
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 588709a9f68e..501e82f5593c 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4017,6 +4017,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>
> .page_enc_status_hc = svm_page_enc_status_hc,
> .get_page_enc_bitmap = svm_get_page_enc_bitmap,
> + .set_page_enc_bitmap = svm_set_page_enc_bitmap,
> };
>
> static struct kvm_x86_init_ops svm_init_ops __initdata = {
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index f087fa7b380c..2ebdcce50312 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -405,6 +405,7 @@ int nested_svm_exit_special(struct vcpu_svm *svm);
> int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
> unsigned long npages, unsigned long enc);
> int svm_get_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap *bmap);
> +int svm_set_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap *bmap);
>
> /* avic.c */
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 937797cfaf9a..c4166d7a0493 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5220,6 +5220,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
> r = kvm_x86_ops.get_page_enc_bitmap(kvm, &bitmap);
> break;
> }
> + case KVM_SET_PAGE_ENC_BITMAP: {
> + struct kvm_page_enc_bitmap bitmap;
> +
> + r = -EFAULT;
> + if (copy_from_user(&bitmap, argp, sizeof(bitmap)))
> + goto out;
> +
> + r = -ENOTTY;
> + if (kvm_x86_ops.set_page_enc_bitmap)
> + r = kvm_x86_ops.set_page_enc_bitmap(kvm, &bitmap);
> + break;
> + }
> default:
> r = -ENOTTY;
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index af62f2afaa5d..2798b17484d0 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1529,6 +1529,7 @@ struct kvm_pv_cmd {
> #define KVM_S390_PV_COMMAND _IOWR(KVMIO, 0xc5, struct kvm_pv_cmd)
>
> #define KVM_GET_PAGE_ENC_BITMAP _IOW(KVMIO, 0xc6, struct kvm_page_enc_bitmap)
> +#define KVM_SET_PAGE_ENC_BITMAP _IOW(KVMIO, 0xc7, struct kvm_page_enc_bitmap)
>
> /* Secure Encrypted Virtualization command */
> enum sev_cmd_id {
> --
> 2.17.1
>

Otherwise, this looks good to me. Thanks for merging the ioctls together.

Reviewed-by: Steve Rutherford <srutherford@xxxxxxxxxx>