From: Venu Busireddy <venu.busireddy@oracle.com>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: Ashish Kalra <Ashish.Kalra@amd.com>,
pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com,
hpa@zytor.com, joro@8bytes.org, bp@suse.de,
thomas.lendacky@amd.com, x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, rientjes@google.com,
srutherford@google.com, luto@kernel.org
Subject: Re: [PATCH v6 01/14] KVM: SVM: Add KVM_SEV SEND_START command
Date: Thu, 2 Apr 2020 11:37:17 -0500 [thread overview]
Message-ID: <20200402163717.GA653926@vbusired-dt> (raw)
In-Reply-To: <89a586e4-8074-0d32-f384-a4597975d129@amd.com>
On 2020-04-02 07:59:54 -0500, Brijesh Singh wrote:
> Hi Venu,
>
> Thanks for the feedback.
>
> On 4/2/20 1:27 AM, Venu Busireddy wrote:
> > On 2020-03-30 06:19:59 +0000, Ashish Kalra wrote:
> >> From: Brijesh Singh <Brijesh.Singh@amd.com>
> >>
> >> The command is used to create an outgoing SEV guest encryption context.
> >>
> >> 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
> >> Reviewed-by: Steve Rutherford <srutherford@google.com>
> >> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> >> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> >> ---
> >> .../virt/kvm/amd-memory-encryption.rst | 27 ++++
> >> arch/x86/kvm/svm.c | 128 ++++++++++++++++++
> >> include/linux/psp-sev.h | 8 +-
> >> include/uapi/linux/kvm.h | 12 ++
> >> 4 files changed, 171 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
> >> index c3129b9ba5cb..4fd34fc5c7a7 100644
> >> --- a/Documentation/virt/kvm/amd-memory-encryption.rst
> >> +++ b/Documentation/virt/kvm/amd-memory-encryption.rst
> >> @@ -263,6 +263,33 @@ Returns: 0 on success, -negative on error
> >> __u32 trans_len;
> >> };
> >>
> >> +10. KVM_SEV_SEND_START
> >> +----------------------
> >> +
> >> +The KVM_SEV_SEND_START command can be used by the hypervisor to create an
> >> +outgoing guest encryption context.
> >> +
> >> +Parameters (in): struct kvm_sev_send_start
> >> +
> >> +Returns: 0 on success, -negative on error
> >> +
> >> +::
> >> + struct kvm_sev_send_start {
> >> + __u32 policy; /* guest policy */
> >> +
> >> + __u64 pdh_cert_uaddr; /* platform Diffie-Hellman certificate */
> >> + __u32 pdh_cert_len;
> >> +
> >> + __u64 plat_certs_uadr; /* platform certificate chain */
> > Could this please be changed to plat_certs_uaddr, as it is referred to
> > in the rest of the code?
> >
> >> + __u32 plat_certs_len;
> >> +
> >> + __u64 amd_certs_uaddr; /* AMD certificate */
> >> + __u32 amd_cert_len;
> > Could this please be changed to amd_certs_len, as it is referred to in
> > the rest of the code?
> >
> >> +
> >> + __u64 session_uaddr; /* Guest session information */
> >> + __u32 session_len;
> >> + };
> >> +
> >> References
> >> ==========
> >>
> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> >> index 50d1ebafe0b3..63d172e974ad 100644
> >> --- a/arch/x86/kvm/svm.c
> >> +++ b/arch/x86/kvm/svm.c
> >> @@ -7149,6 +7149,131 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
> >> return ret;
> >> }
> >>
> >> +/* Userspace wants to query session length. */
> >> +static int
> >> +__sev_send_start_query_session_length(struct kvm *kvm, struct kvm_sev_cmd *argp,
> >> + struct kvm_sev_send_start *params)
> >> +{
> >> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> >> + struct sev_data_send_start *data;
> >> + int ret;
> >> +
> >> + data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
> >> + if (data == NULL)
> >> + return -ENOMEM;
> >> +
> >> + data->handle = sev->handle;
> >> + ret = sev_issue_cmd(kvm, SEV_CMD_SEND_START, data, &argp->error);
> >> +
> >> + params->session_len = data->session_len;
> >> + if (copy_to_user((void __user *)(uintptr_t)argp->data, params,
> >> + sizeof(struct kvm_sev_send_start)))
> >> + ret = -EFAULT;
> >> +
> >> + kfree(data);
> >> + return ret;
> >> +}
> >> +
> >> +static int sev_send_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> >> +{
> >> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> >> + struct sev_data_send_start *data;
> >> + struct kvm_sev_send_start params;
> >> + void *amd_certs, *session_data;
> >> + void *pdh_cert, *plat_certs;
> >> + int ret;
> >> +
> >> + if (!sev_guest(kvm))
> >> + return -ENOTTY;
> >> +
> >> + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data,
> >> + sizeof(struct kvm_sev_send_start)))
> >> + return -EFAULT;
> >> +
> >> + /* if session_len is zero, userspace wants to query the session length */
> >> + if (!params.session_len)
> >> + return __sev_send_start_query_session_length(kvm, argp,
> >> + ¶ms);
> >> +
> >> + /* some sanity checks */
> >> + if (!params.pdh_cert_uaddr || !params.pdh_cert_len ||
> >> + !params.session_uaddr || params.session_len > SEV_FW_BLOB_MAX_SIZE)
> >> + return -EINVAL;
> >> +
> >> + /* allocate the memory to hold the session data blob */
> >> + session_data = kmalloc(params.session_len, GFP_KERNEL_ACCOUNT);
> >> + if (!session_data)
> >> + return -ENOMEM;
> >> +
> >> + /* copy the certificate blobs from userspace */
> >> + pdh_cert = psp_copy_user_blob(params.pdh_cert_uaddr,
> >> + params.pdh_cert_len);
> >> + if (IS_ERR(pdh_cert)) {
> >> + ret = PTR_ERR(pdh_cert);
> >> + goto e_free_session;
> >> + }
> >> +
> >> + plat_certs = psp_copy_user_blob(params.plat_certs_uaddr,
> >> + params.plat_certs_len);
> >> + if (IS_ERR(plat_certs)) {
> >> + ret = PTR_ERR(plat_certs);
> >> + goto e_free_pdh;
> >> + }
> >> +
> >> + amd_certs = psp_copy_user_blob(params.amd_certs_uaddr,
> >> + params.amd_certs_len);
> >> + if (IS_ERR(amd_certs)) {
> >> + ret = PTR_ERR(amd_certs);
> >> + goto e_free_plat_cert;
> >> + }
> >> +
> >> + data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
> >> + if (data == NULL) {
> >> + ret = -ENOMEM;
> >> + goto e_free_amd_cert;
> >> + }
> >> +
> >> + /* populate the FW SEND_START field with system physical address */
> >> + data->pdh_cert_address = __psp_pa(pdh_cert);
> >> + data->pdh_cert_len = params.pdh_cert_len;
> >> + data->plat_certs_address = __psp_pa(plat_certs);
> >> + data->plat_certs_len = params.plat_certs_len;
> >> + data->amd_certs_address = __psp_pa(amd_certs);
> >> + data->amd_certs_len = params.amd_certs_len;
> >> + data->session_address = __psp_pa(session_data);
> >> + data->session_len = params.session_len;
> >> + data->handle = sev->handle;
> >> +
> >> + ret = sev_issue_cmd(kvm, SEV_CMD_SEND_START, data, &argp->error);
> >> +
> >> + if (ret)
> >> + goto e_free;
> >> +
> >> + if (copy_to_user((void __user *)(uintptr_t) params.session_uaddr,
> >> + session_data, params.session_len)) {
> >> + ret = -EFAULT;
> >> + goto e_free;
> >> + }
> > To optimize the amount of data being copied to user space, could the
> > above section of code changed as follows?
> >
> > params.session_len = data->session_len;
> > if (copy_to_user((void __user *)(uintptr_t) params.session_uaddr,
> > session_data, params.session_len)) {
> > ret = -EFAULT;
> > goto e_free;
> > }
>
>
> We should not be using the data->session_len, it will cause -EFAULT when
> user has not allocated enough space in the session_uaddr. Lets consider
> the case where user passes session_len=10 but firmware thinks the
> session length should be 64. In that case the data->session_len will
> contains a value of 64 but userspace has allocated space for 10 bytes
> and copy_to_user() will fail. If we are really concern about the amount
> of data getting copied to userspace then use min_t(size_t,
> params.session_len, data->session_len).
We are allocating a buffer of params.session_len size and passing that
buffer, and that length via data->session_len, to the firmware. Why would
the firmware set data->session_len to a larger value, in spite of telling
it that the buffer is only params.session_len long? I thought that only
the reverse is possible, that is, the user sets the params.session_len
to the MAX, but the session data is actually smaller than that size.
Also, if for whatever reason the firmware sets data->session_len to
a larger value than what is passed, what is the user space expected
to do when the call returns? If the user space tries to access
params.session_len amount of data, it will possibly get a memory access
violation, because it did not originally allocate that large a buffer.
If we do go with using min_t(size_t, params.session_len,
data->session_len), then params.session_len should also be set to the
smaller of the two, right?
> >> +
> >> + params.policy = data->policy;
> >> + params.session_len = data->session_len;
> >> + if (copy_to_user((void __user *)(uintptr_t)argp->data, ¶ms,
> >> + sizeof(struct kvm_sev_send_start)))
> >> + ret = -EFAULT;
> > Since the only fields that are changed in the kvm_sev_send_start structure
> > are session_len and policy, why do we need to copy the entire structure
> > back to the user? Why not just those two values? Please see the changes
> > proposed to kvm_sev_send_start structure further below to accomplish this.
>
> I think we also need to consider the code readability while saving the
> CPU cycles. This is very small structure. By duplicating into two calls
> #1 copy params.policy and #2 copy params.session_len we will add more
> CPU cycle. And, If we get creative and rearrange the structure then code
> readability is lost because now the copy will depend on how the
> structure is layout in the memory.
I was not recommending splitting that call into two. That would certainly
be more expensive, than copying the entire structure. That is the reason
why I suggested reordering the members of kvm_sev_send_start. Isn't
there plenty of code where structures are defined in a way to keep the
data movement efficient? :-)
Please see my other comment below.
>
> >
> > params.policy = data->policy;
> > if (copy_to_user((void __user *)(uintptr_t)argp->data, ¶ms,
> > sizeof(params.policy) + sizeof(params.session_len))
> > ret = -EFAULT;
> >> +
> >> +e_free:
> >> + kfree(data);
> >> +e_free_amd_cert:
> >> + kfree(amd_certs);
> >> +e_free_plat_cert:
> >> + kfree(plat_certs);
> >> +e_free_pdh:
> >> + kfree(pdh_cert);
> >> +e_free_session:
> >> + kfree(session_data);
> >> + return ret;
> >> +}
> >> +
> >> static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> >> {
> >> struct kvm_sev_cmd sev_cmd;
> >> @@ -7193,6 +7318,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> >> case KVM_SEV_LAUNCH_SECRET:
> >> r = sev_launch_secret(kvm, &sev_cmd);
> >> break;
> >> + case KVM_SEV_SEND_START:
> >> + r = sev_send_start(kvm, &sev_cmd);
> >> + break;
> >> default:
> >> r = -EINVAL;
> >> goto out;
> >> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> >> index 5167bf2bfc75..9f63b9d48b63 100644
> >> --- a/include/linux/psp-sev.h
> >> +++ b/include/linux/psp-sev.h
> >> @@ -323,11 +323,11 @@ struct sev_data_send_start {
> >> u64 pdh_cert_address; /* In */
> >> u32 pdh_cert_len; /* In */
> >> u32 reserved1;
> >> - u64 plat_cert_address; /* In */
> >> - u32 plat_cert_len; /* In */
> >> + u64 plat_certs_address; /* In */
> >> + u32 plat_certs_len; /* In */
> >> u32 reserved2;
> >> - u64 amd_cert_address; /* In */
> >> - u32 amd_cert_len; /* In */
> >> + u64 amd_certs_address; /* In */
> >> + u32 amd_certs_len; /* In */
> >> u32 reserved3;
> >> u64 session_address; /* In */
> >> u32 session_len; /* In/Out */
> >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> >> index 4b95f9a31a2f..17bef4c245e1 100644
> >> --- a/include/uapi/linux/kvm.h
> >> +++ b/include/uapi/linux/kvm.h
> >> @@ -1558,6 +1558,18 @@ struct kvm_sev_dbg {
> >> __u32 len;
> >> };
> >>
> >> +struct kvm_sev_send_start {
> >> + __u32 policy;
> >> + __u64 pdh_cert_uaddr;
> >> + __u32 pdh_cert_len;
> >> + __u64 plat_certs_uaddr;
> >> + __u32 plat_certs_len;
> >> + __u64 amd_certs_uaddr;
> >> + __u32 amd_certs_len;
> >> + __u64 session_uaddr;
> >> + __u32 session_len;
> >> +};
> > Redo this structure as below:
> >
> > struct kvm_sev_send_start {
> > __u32 policy;
> > __u32 session_len;
> > __u64 session_uaddr;
> > __u64 pdh_cert_uaddr;
> > __u32 pdh_cert_len;
> > __u64 plat_certs_uaddr;
> > __u32 plat_certs_len;
> > __u64 amd_certs_uaddr;
> > __u32 amd_certs_len;
> > };
> >
> > Or as below, just to make it look better.
> >
> > struct kvm_sev_send_start {
> > __u32 policy;
> > __u32 session_len;
> > __u64 session_uaddr;
> > __u32 pdh_cert_len;
> > __u64 pdh_cert_uaddr;
> > __u32 plat_certs_len;
> > __u64 plat_certs_uaddr;
> > __u32 amd_certs_len;
> > __u64 amd_certs_uaddr;
> > };
> >
>
> Wherever applicable, I tried best to not divert from the SEV spec
> structure layout. Anyone who is reading the SEV FW spec will see a
> similar structure layout in the KVM/PSP header files. I would prefer to
> stick to that approach.
This structure is in uapi, and is anyway different from the
sev_data_send_start, right? Does it really need to stay close to the
firmware structure layout? Just because the firmware folks thought of
a structure layout, that should not prevent our code to be efficient.
>
>
> >> +
> >> #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)
> >> --
> >> 2.17.1
> >>
next prev parent reply other threads:[~2020-04-02 16:37 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 6:19 [PATCH v6 00/14] Add AMD SEV guest live migration support Ashish Kalra
2020-03-30 6:19 ` [PATCH v6 01/14] KVM: SVM: Add KVM_SEV SEND_START command Ashish Kalra
2020-04-02 6:27 ` Venu Busireddy
2020-04-02 12:59 ` Brijesh Singh
2020-04-02 16:37 ` Venu Busireddy [this message]
2020-04-02 18:04 ` Brijesh Singh
2020-04-02 18:57 ` Venu Busireddy
2020-04-02 19:17 ` Brijesh Singh
2020-04-02 19:43 ` Venu Busireddy
2020-04-02 20:04 ` Brijesh Singh
2020-04-02 20:19 ` Venu Busireddy
2020-04-02 17:51 ` Krish Sadhukhan
2020-04-02 18:38 ` Brijesh Singh
2020-03-30 6:20 ` [PATCH v6 02/14] KVM: SVM: Add KVM_SEND_UPDATE_DATA command Ashish Kalra
2020-04-02 17:55 ` Venu Busireddy
2020-04-02 20:13 ` Krish Sadhukhan
2020-03-30 6:20 ` [PATCH v6 03/14] KVM: SVM: Add KVM_SEV_SEND_FINISH command Ashish Kalra
2020-04-02 18:17 ` Venu Busireddy
2020-04-02 20:15 ` Krish Sadhukhan
2020-03-30 6:21 ` [PATCH v6 04/14] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command Ashish Kalra
2020-04-02 21:35 ` Venu Busireddy
2020-04-02 22:09 ` Krish Sadhukhan
2020-03-30 6:21 ` [PATCH v6 05/14] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command Ashish Kalra
2020-04-02 22:25 ` Krish Sadhukhan
2020-04-02 22:29 ` Venu Busireddy
2020-04-07 0:49 ` Steve Rutherford
2020-03-30 6:21 ` [PATCH v6 06/14] KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command Ashish Kalra
2020-04-02 22:24 ` Venu Busireddy
2020-04-02 22:27 ` Krish Sadhukhan
2020-04-07 0:57 ` Steve Rutherford
2020-03-30 6:21 ` [PATCH v6 07/14] KVM: x86: Add AMD SEV specific Hypercall3 Ashish Kalra
2020-04-02 22:36 ` Venu Busireddy
2020-04-02 23:54 ` Krish Sadhukhan
2020-04-07 1:22 ` Steve Rutherford
2020-03-30 6:22 ` [PATCH v6 08/14] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall Ashish Kalra
2020-04-03 0:00 ` Venu Busireddy
2020-04-03 1:31 ` Krish Sadhukhan
2020-04-03 1:57 ` Ashish Kalra
2020-04-03 2:58 ` Ashish Kalra
2020-04-06 22:27 ` Krish Sadhukhan
2020-04-07 2:17 ` Steve Rutherford
2020-04-07 5:27 ` Ashish Kalra
2020-04-08 0:01 ` Steve Rutherford
2020-04-08 0:29 ` Brijesh Singh
2020-04-08 0:35 ` Steve Rutherford
2020-04-08 1:17 ` Ashish Kalra
2020-04-08 1:38 ` Steve Rutherford
2020-04-08 2:34 ` Brijesh Singh
2020-04-08 3:18 ` Ashish Kalra
2020-04-09 16:18 ` Ashish Kalra
2020-04-09 20:41 ` Steve Rutherford
2020-03-30 6:22 ` [PATCH v6 09/14] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl Ashish Kalra
2020-04-03 18:30 ` Venu Busireddy
2020-04-03 20:18 ` Krish Sadhukhan
2020-04-03 20:47 ` Ashish Kalra
2020-04-06 22:07 ` Krish Sadhukhan
2020-04-03 20:55 ` Venu Busireddy
2020-04-03 21:01 ` Ashish Kalra
2020-03-30 6:22 ` [PATCH v6 10/14] mm: x86: Invoke hypercall when page encryption status is changed Ashish Kalra
2020-04-03 21:07 ` Krish Sadhukhan
2020-04-03 21:30 ` Ashish Kalra
2020-04-03 21:36 ` Venu Busireddy
2020-03-30 6:22 ` [PATCH v6 11/14] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl Ashish Kalra
2020-04-03 21:10 ` Krish Sadhukhan
2020-04-03 21:46 ` Venu Busireddy
2020-04-08 0:26 ` Steve Rutherford
2020-04-08 1:48 ` Ashish Kalra
2020-04-10 0:06 ` Steve Rutherford
2020-04-10 1:23 ` Ashish Kalra
2020-04-10 18:08 ` Steve Rutherford
2020-03-30 6:23 ` [PATCH v6 12/14] KVM: x86: Introduce KVM_PAGE_ENC_BITMAP_RESET ioctl Ashish Kalra
2020-04-03 21:14 ` Krish Sadhukhan
2020-04-03 21:45 ` Ashish Kalra
2020-04-06 18:52 ` Krish Sadhukhan
2020-04-08 1:25 ` Steve Rutherford
2020-04-08 1:52 ` Ashish Kalra
2020-04-10 0:59 ` Steve Rutherford
2020-04-10 1:34 ` Ashish Kalra
2020-04-10 18:14 ` Steve Rutherford
2020-04-10 20:16 ` Steve Rutherford
2020-04-10 20:18 ` Steve Rutherford
2020-04-10 20:55 ` Kalra, Ashish
2020-04-10 21:42 ` Brijesh Singh
2020-04-10 21:46 ` Sean Christopherson
2020-04-10 21:58 ` Brijesh Singh
2020-04-10 22:02 ` Brijesh Singh
2020-04-11 0:35 ` Ashish Kalra
2020-04-03 22:01 ` Venu Busireddy
2020-03-30 6:23 ` [PATCH v6 13/14] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR Ashish Kalra
2020-03-30 15:52 ` Brijesh Singh
2020-03-30 16:42 ` Ashish Kalra
[not found] ` <20200330162730.GA21567@ashkalra_ubuntu_server>
[not found] ` <1de5e95f-4485-f2ff-aba8-aa8b15564796@amd.com>
[not found] ` <20200331171336.GA24050@ashkalra_ubuntu_server>
[not found] ` <20200401070931.GA8562@ashkalra_ubuntu_server>
2020-04-02 23:29 ` Ashish Kalra
2020-04-03 23:46 ` Krish Sadhukhan
2020-03-30 6:23 ` [PATCH v6 14/14] KVM: x86: Add kexec support for SEV Live Migration Ashish Kalra
2020-03-30 16:00 ` Brijesh Singh
2020-03-30 16:45 ` Ashish Kalra
2020-03-31 14:26 ` Brijesh Singh
2020-04-02 23:34 ` Ashish Kalra
2020-04-03 12:57 ` Dave Young
2020-04-04 0:55 ` Krish Sadhukhan
2020-04-04 21:57 ` Ashish Kalra
2020-04-06 18:37 ` Krish Sadhukhan
2020-03-30 17:24 ` [PATCH v6 00/14] Add AMD SEV guest live migration support Venu Busireddy
2020-03-30 18:28 ` Ashish Kalra
2020-03-30 19:13 ` Venu Busireddy
2020-03-30 21:52 ` Ashish Kalra
2020-03-31 14:42 ` Venu Busireddy
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