Re: [RFC PATCH v1 02/10] KVM: SVM: Add KVM_SEND_UPDATE_DATA command

["Lendacky, Thomas" <Thomas.Lendacky@amd.com>]

On 4/24/19 11:10 AM, Singh, Brijesh wrote:
> The command is used for encrypting the guest memory region using the encryption
> context created with KVM_SEV_SEND_START.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: x86@kernel.org
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  .../virtual/kvm/amd-memory-encryption.rst     |  23 ++++
>  arch/x86/kvm/svm.c                            | 128 +++++++++++++++++-
>  include/uapi/linux/kvm.h                      |   9 ++
>  3 files changed, 157 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/amd-memory-encryption.rst b/Documentation/virtual/kvm/amd-memory-encryption.rst
> index 340ac4f87321..a0208e171489 100644
> --- a/Documentation/virtual/kvm/amd-memory-encryption.rst
> +++ b/Documentation/virtual/kvm/amd-memory-encryption.rst
> @@ -262,6 +262,29 @@ Returns: 0 on success, -negative on error
>                  __u32 amd_cert_len;
>          };
>  
> +11. KVM_SEV_SEND_UPDATE_DATA
> +----------------------------
> +
> +The KVM_SEV_SEND_UPDATE_DATA command can be used by the hypervisor to encrypt the
> +outgoing guest memory region with encryption context creating using KVM_SEV_SEND_START.

with the encryption context created using...

> +
> +Parameters (in): struct kvm_sev_send_update_data
> +
> +Returns: 0 on success, -negative on error
> +
> +::
> +
> +        struct kvm_sev_launch_send_update_data {
> +                __u64 hdr_uaddr;        /* userspace address containing the packet header */
> +                __u32 hdr_len;
> +
> +                __u64 guest_uaddr;      /* the source memory region to be encrypted */
> +                __u32 guest_len;
> +
> +                __u64 trans_uaddr;      /* the destition memory region  */
> +                __u32 trans_len;
> +        };
> +
>  References
>  ==========
>  
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 4c2a225ba546..a1cfd36d6195 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -418,6 +418,7 @@ enum {
>  
>  static unsigned int max_sev_asid;
>  static unsigned int min_sev_asid;
> +static unsigned long me_mask;

sev_me_mask ?

>  static unsigned long *sev_asid_bitmap;
>  #define __sme_page_pa(x) __sme_set(page_to_pfn(x) << PAGE_SHIFT)
>  
> @@ -1216,15 +1217,21 @@ static int avic_ga_log_notifier(u32 ga_tag)
>  static __init int sev_hardware_setup(void)
>  {
>  	struct sev_user_data_status *status;
> +	int eax, ebx;
>  	int rc;
>  
> -	/* Maximum number of encrypted guests supported simultaneously */
> -	max_sev_asid = cpuid_ecx(0x8000001F);
> +	/*
> +	 * Query the memory encryption information.
> +	 *  EBX:  Bit 0:5 Pagetable bit position used to indicate encryption (aka Cbit).
> +	 *  ECX:  Maximum number of encrypted guests supported simultaneously.
> +	 *  EDX:  Minimum ASID value that should be used for SEV guest.
> +	 */
> +	cpuid(0x8000001f, &eax, &ebx, &max_sev_asid, &min_sev_asid);
>  
>  	if (!max_sev_asid)
>  		return 1;
>  
> -	/* Minimum ASID value that should be used for SEV guest */
> +	me_mask = 1UL << (ebx & 0x3f);
>  	min_sev_asid = cpuid_edx(0x8000001F);

You can remove this since you obtained it with the cpuid() call above.

>  
>  	/* Initialize SEV ASID bitmap */
> @@ -7053,6 +7060,118 @@ static int sev_send_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	return ret;
>  }
>  
> +static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> +	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +	struct sev_data_send_update_data *data;
> +	struct kvm_sev_send_update_data params;
> +	void *hdr = NULL, *trans_data = NULL;
> +	struct page **guest_page = NULL;
> +	unsigned long n;
> +	int ret, offset;
> +
> +	if (!sev_guest(kvm))
> +		return -ENOTTY;
> +
> +	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
> +			sizeof(struct kvm_sev_send_update_data)))
> +		return -EFAULT;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	/* userspace wants to query either header or trans length */
> +	if (!params.trans_len || !params.hdr_len)
> +		goto cmd;
> +
> +	ret = -EINVAL;
> +	if (!params.trans_uaddr || !params.guest_uaddr ||
> +	    !params.guest_len || !params.hdr_uaddr)
> +		goto e_free;
> +
> +	/* Check if we are crossing the page boundry */
> +	ret = -EINVAL;
> +	offset = params.guest_uaddr & (PAGE_SIZE - 1);
> +	if ((params.guest_len + offset > PAGE_SIZE))
> +		goto e_free;
> +
> +	ret = -ENOMEM;
> +	hdr = kmalloc(params.hdr_len, GFP_KERNEL);
> +	if (!hdr)
> +		goto e_free;
> +
> +	data->hdr_address = __psp_pa(hdr);
> +	data->hdr_len = params.hdr_len;
> +
> +	ret = -ENOMEM;
> +	trans_data = kmalloc(params.trans_len, GFP_KERNEL);
> +	if (!trans_data)
> +		goto e_free;
> +
> +	data->trans_address = __psp_pa(trans_data);
> +	data->trans_len = params.trans_len;
> +
> +	/* Pin guest memory */
> +	ret = -EFAULT;
> +	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
> +				    PAGE_SIZE, &n, 0);
> +	if (!guest_page)
> +		goto e_free;
> +
> +	data->guest_address = __sme_page_pa(guest_page[0]) + offset;

If the C-bit needs to be set regardless below, then you don't need the
__sme version of this.

> +	data->guest_len = params.guest_len;
> +
> +	/*
> +	 * The SEND_UPDATE_DATA command requires C-bit to be always set.
> +	 * The __sme_page_pa() takes care of setting the C-bit only when SME
> +	 * is enabled on the host. But we need to set the C-bit regarless of

regardless

Thanks,
Tom

> +	 * the SME state.
> +	 */
> +	data->guest_address |= me_mask;
> +
> +	/* flush the caches to ensure that DRAM has recent contents */
> +	sev_clflush_pages(guest_page, 1);
> +
> +cmd:
> +	data->handle = sev->handle;
> +	ret = sev_issue_cmd(kvm, SEV_CMD_SEND_UPDATE_DATA, data, &argp->error);
> +
> +	/* userspace asked for header or trans length and FW responded with data */
> +	if (!params.trans_len || !params.hdr_len) {
> +		params.hdr_len = data->hdr_len;
> +		params.trans_len = data->trans_len;
> +		goto done;
> +	}
> +
> +	if (ret)
> +		goto e_unpin;
> +
> +	/* copy transport buffer to user space */
> +	if (copy_to_user((void __user *)(uintptr_t)params.trans_uaddr,
> +			 trans_data, params.trans_len)) {
> +		ret = -EFAULT;
> +		goto e_unpin;
> +	}
> +
> +	/* copy packet header to userspace */
> +	if (copy_to_user((void __user *)(uintptr_t)params.hdr_uaddr, hdr, params.hdr_len))
> +		ret = -EFAULT;
> +
> +e_unpin:
> +	sev_unpin_memory(kvm, guest_page, n);
> +done:
> +	if (copy_to_user((void __user *)(uintptr_t)argp->data, &params,
> +			sizeof(struct kvm_sev_send_update_data)))
> +		ret = -EFAULT;
> +e_free:
> +	kfree(data);
> +	kfree(trans_data);
> +	kfree(hdr);
> +
> +	return ret;
> +}
> +
>  static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>  {
>  	struct kvm_sev_cmd sev_cmd;
> @@ -7097,6 +7216,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>  	case KVM_SEV_SEND_START:
>  		r = sev_send_start(kvm, &sev_cmd);
>  		break;
> +	case KVM_SEV_SEND_UPDATE_DATA:
> +		r = sev_send_update_data(kvm, &sev_cmd);
> +		break;
>  	default:
>  		r = -EINVAL;
>  		goto out;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index f425418bec13..0bee91bba329 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1532,6 +1532,15 @@ struct kvm_sev_send_start {
>  	__u32 session_len;
>  };
>  
> +struct kvm_sev_send_update_data {
> +	__u64 hdr_uaddr;
> +	__u32 hdr_len;
> +	__u64 guest_uaddr;
> +	__u32 guest_len;
> +	__u64 trans_uaddr;
> +	__u32 trans_len;
> +};
> +
>  #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
>  #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
>  #define KVM_DEV_ASSIGN_MASK_INTX	(1 << 2)
>