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[PATCH v2] qapi, target/i386/sev: Add cpu0-id to query-sev-capabilities

Dov Murik posted 1 patch 2 years, 2 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20220224061405.1959756-1-dovmurik@linux.ibm.com
Maintainers: Paolo Bonzini <pbonzini@redhat.com>, Eric Blake <eblake@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Markus Armbruster <armbru@redhat.com>
There is a newer version of this series
qapi/misc-target.json |  4 ++++
target/i386/sev.c     | 27 +++++++++++++++++++++++++++
2 files changed, 31 insertions(+)
[PATCH v2] qapi, target/i386/sev: Add cpu0-id to query-sev-capabilities
Posted by Dov Murik 2 years, 2 months ago 
Add a new field 'cpu0-id' to the response of query-sev-capabilities QMP
command.  The value of the field is the base64-encoded 64-byte unique ID
of the CPU0 (socket 0), which can be used to retrieve the signed CEK of
the CPU from AMD's Key Distribution Service (KDS).

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

---

v2:
- change encoding to Base64 (thanks Daniel)
- rename constant to SEV_CPU_UNIQUE_ID_LEN
---
 qapi/misc-target.json |  4 ++++
 target/i386/sev.c     | 27 +++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/qapi/misc-target.json b/qapi/misc-target.json
index 4bc45d2474..c6d9ad69e1 100644
--- a/qapi/misc-target.json
+++ b/qapi/misc-target.json
@@ -177,6 +177,8 @@
 #
 # @cert-chain:  PDH certificate chain (base64 encoded)
 #
+# @cpu0-id: 64-byte unique ID of CPU0 (base64 encoded) (since 7.0)
+#
 # @cbitpos: C-bit location in page table entry
 #
 # @reduced-phys-bits: Number of physical Address bit reduction when SEV is
@@ -187,6 +189,7 @@
 { 'struct': 'SevCapability',
   'data': { 'pdh': 'str',
             'cert-chain': 'str',
+            'cpu0-id': 'str',
             'cbitpos': 'int',
             'reduced-phys-bits': 'int'},
   'if': 'TARGET_I386' }
@@ -205,6 +208,7 @@
 #
 # -> { "execute": "query-sev-capabilities" }
 # <- { "return": { "pdh": "8CCDD8DDD", "cert-chain": "888CCCDDDEE",
+#                  "cpu0-id": "2lvmGwo+...61iEinw==",
 #                  "cbitpos": 47, "reduced-phys-bits": 5}}
 #
 ##
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 025ff7a6f8..d3d2680e16 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -82,6 +82,8 @@ struct SevGuestState {
 #define DEFAULT_GUEST_POLICY    0x1 /* disable debug */
 #define DEFAULT_SEV_DEVICE      "/dev/sev"
 
+#define SEV_CPU_UNIQUE_ID_LEN   64
+
 #define SEV_INFO_BLOCK_GUID     "00f771de-1a7e-4fcb-890e-68c77e2fb44e"
 typedef struct __attribute__((__packed__)) SevInfoBlock {
     /* SEV-ES Reset Vector Address */
@@ -531,11 +533,31 @@ e_free:
     return 1;
 }
 
+static int
+sev_get_id(int fd, guchar *id_buf, size_t id_buf_len, Error **errp)
+{
+    struct sev_user_data_get_id2 id = {
+        .address = (unsigned long)id_buf,
+        .length = id_buf_len
+    };
+    int err, r;
+
+    r = sev_platform_ioctl(fd, SEV_GET_ID2, &id, &err);
+    if (r < 0) {
+        error_setg(errp, "SEV: Failed to get ID ret=%d fw_err=%d (%s)",
+                   r, err, fw_error_to_str(err));
+        return 1;
+    }
+
+    return 0;
+}
+
 static SevCapability *sev_get_capabilities(Error **errp)
 {
     SevCapability *cap = NULL;
     guchar *pdh_data = NULL;
     guchar *cert_chain_data = NULL;
+    guchar cpu0_id[SEV_CPU_UNIQUE_ID_LEN];
     size_t pdh_len = 0, cert_chain_len = 0;
     uint32_t ebx;
     int fd;
@@ -561,9 +583,14 @@ static SevCapability *sev_get_capabilities(Error **errp)
         goto out;
     }
 
+    if (sev_get_id(fd, cpu0_id, sizeof(cpu0_id), errp)) {
+        goto out;
+    }
+
     cap = g_new0(SevCapability, 1);
     cap->pdh = g_base64_encode(pdh_data, pdh_len);
     cap->cert_chain = g_base64_encode(cert_chain_data, cert_chain_len);
+    cap->cpu0_id = g_base64_encode(cpu0_id, sizeof(cpu0_id));
 
     host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL);
     cap->cbitpos = ebx & 0x3f;
-- 
2.25.1
Re: [PATCH v2] qapi, target/i386/sev: Add cpu0-id to query-sev-capabilities
Posted by Daniel P. Berrangé 2 years, 2 months ago 
On Thu, Feb 24, 2022 at 06:14:05AM +0000, Dov Murik wrote:
> Add a new field 'cpu0-id' to the response of query-sev-capabilities QMP
> command.  The value of the field is the base64-encoded 64-byte unique ID
> of the CPU0 (socket 0), which can be used to retrieve the signed CEK of
> the CPU from AMD's Key Distribution Service (KDS).
> 
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> 
> ---
> 
> v2:
> - change encoding to Base64 (thanks Daniel)
> - rename constant to SEV_CPU_UNIQUE_ID_LEN
> ---
>  qapi/misc-target.json |  4 ++++
>  target/i386/sev.c     | 27 +++++++++++++++++++++++++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/qapi/misc-target.json b/qapi/misc-target.json
> index 4bc45d2474..c6d9ad69e1 100644
> --- a/qapi/misc-target.json
> +++ b/qapi/misc-target.json
> @@ -177,6 +177,8 @@
>  #
>  # @cert-chain:  PDH certificate chain (base64 encoded)
>  #
> +# @cpu0-id: 64-byte unique ID of CPU0 (base64 encoded) (since 7.0)
> +#
>  # @cbitpos: C-bit location in page table entry
>  #
>  # @reduced-phys-bits: Number of physical Address bit reduction when SEV is
> @@ -187,6 +189,7 @@
>  { 'struct': 'SevCapability',
>    'data': { 'pdh': 'str',
>              'cert-chain': 'str',
> +            'cpu0-id': 'str',
>              'cbitpos': 'int',
>              'reduced-phys-bits': 'int'},
>    'if': 'TARGET_I386' }
> @@ -205,6 +208,7 @@
>  #
>  # -> { "execute": "query-sev-capabilities" }
>  # <- { "return": { "pdh": "8CCDD8DDD", "cert-chain": "888CCCDDDEE",
> +#                  "cpu0-id": "2lvmGwo+...61iEinw==",
>  #                  "cbitpos": 47, "reduced-phys-bits": 5}}
>  #
>  ##
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index 025ff7a6f8..d3d2680e16 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -82,6 +82,8 @@ struct SevGuestState {
>  #define DEFAULT_GUEST_POLICY    0x1 /* disable debug */
>  #define DEFAULT_SEV_DEVICE      "/dev/sev"
>  
> +#define SEV_CPU_UNIQUE_ID_LEN   64

Is this fixed size actually guaranteed by AMD ?  In reading the spec
for "GET_ID" it feels like they're intentionally not specifying a
fixed length, pushing towards querying once and then re-trying with
the reported buffer size:

   "If the value of the ID_LEN field is too small, an 
    INVALID_LENGTH error is returned and the minimum 
    required length is written to the field"

I didn't find where it says 64 bytes exactly.

> +
>  #define SEV_INFO_BLOCK_GUID     "00f771de-1a7e-4fcb-890e-68c77e2fb44e"
>  typedef struct __attribute__((__packed__)) SevInfoBlock {
>      /* SEV-ES Reset Vector Address */
> @@ -531,11 +533,31 @@ e_free:
>      return 1;
>  }
>  
> +static int
> +sev_get_id(int fd, guchar *id_buf, size_t id_buf_len, Error **errp)
> +{
> +    struct sev_user_data_get_id2 id = {
> +        .address = (unsigned long)id_buf,
> +        .length = id_buf_len
> +    };
> +    int err, r;
> +
> +    r = sev_platform_ioctl(fd, SEV_GET_ID2, &id, &err);
> +    if (r < 0) {
> +        error_setg(errp, "SEV: Failed to get ID ret=%d fw_err=%d (%s)",
> +                   r, err, fw_error_to_str(err));
> +        return 1;
> +    }
> +
> +    return 0;
> +}
> +
>  static SevCapability *sev_get_capabilities(Error **errp)
>  {
>      SevCapability *cap = NULL;
>      guchar *pdh_data = NULL;
>      guchar *cert_chain_data = NULL;
> +    guchar cpu0_id[SEV_CPU_UNIQUE_ID_LEN];
>      size_t pdh_len = 0, cert_chain_len = 0;
>      uint32_t ebx;
>      int fd;
> @@ -561,9 +583,14 @@ static SevCapability *sev_get_capabilities(Error **errp)
>          goto out;
>      }
>  
> +    if (sev_get_id(fd, cpu0_id, sizeof(cpu0_id), errp)) {
> +        goto out;
> +    }
> +
>      cap = g_new0(SevCapability, 1);
>      cap->pdh = g_base64_encode(pdh_data, pdh_len);
>      cap->cert_chain = g_base64_encode(cert_chain_data, cert_chain_len);
> +    cap->cpu0_id = g_base64_encode(cpu0_id, sizeof(cpu0_id));
>  
>      host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL);
>      cap->cbitpos = ebx & 0x3f;
> -- 
> 2.25.1
> 

Regards,
Daniel
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Re: [PATCH v2] qapi, target/i386/sev: Add cpu0-id to query-sev-capabilities
Posted by Dov Murik 2 years, 2 months ago 

On 24/02/2022 10:59, Daniel P. Berrangé wrote:
> On Thu, Feb 24, 2022 at 06:14:05AM +0000, Dov Murik wrote:
>> Add a new field 'cpu0-id' to the response of query-sev-capabilities QMP
>> command.  The value of the field is the base64-encoded 64-byte unique ID
>> of the CPU0 (socket 0), which can be used to retrieve the signed CEK of
>> the CPU from AMD's Key Distribution Service (KDS).
>>
>> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
>>
>> ---
>>
>> v2:
>> - change encoding to Base64 (thanks Daniel)
>> - rename constant to SEV_CPU_UNIQUE_ID_LEN
>> ---
>>  qapi/misc-target.json |  4 ++++
>>  target/i386/sev.c     | 27 +++++++++++++++++++++++++++
>>  2 files changed, 31 insertions(+)
>>
>> diff --git a/qapi/misc-target.json b/qapi/misc-target.json
>> index 4bc45d2474..c6d9ad69e1 100644
>> --- a/qapi/misc-target.json
>> +++ b/qapi/misc-target.json
>> @@ -177,6 +177,8 @@
>>  #
>>  # @cert-chain:  PDH certificate chain (base64 encoded)
>>  #
>> +# @cpu0-id: 64-byte unique ID of CPU0 (base64 encoded) (since 7.0)
>> +#
>>  # @cbitpos: C-bit location in page table entry
>>  #
>>  # @reduced-phys-bits: Number of physical Address bit reduction when SEV is
>> @@ -187,6 +189,7 @@
>>  { 'struct': 'SevCapability',
>>    'data': { 'pdh': 'str',
>>              'cert-chain': 'str',
>> +            'cpu0-id': 'str',
>>              'cbitpos': 'int',
>>              'reduced-phys-bits': 'int'},
>>    'if': 'TARGET_I386' }
>> @@ -205,6 +208,7 @@
>>  #
>>  # -> { "execute": "query-sev-capabilities" }
>>  # <- { "return": { "pdh": "8CCDD8DDD", "cert-chain": "888CCCDDDEE",
>> +#                  "cpu0-id": "2lvmGwo+...61iEinw==",
>>  #                  "cbitpos": 47, "reduced-phys-bits": 5}}
>>  #
>>  ##
>> diff --git a/target/i386/sev.c b/target/i386/sev.c
>> index 025ff7a6f8..d3d2680e16 100644
>> --- a/target/i386/sev.c
>> +++ b/target/i386/sev.c
>> @@ -82,6 +82,8 @@ struct SevGuestState {
>>  #define DEFAULT_GUEST_POLICY    0x1 /* disable debug */
>>  #define DEFAULT_SEV_DEVICE      "/dev/sev"
>>  
>> +#define SEV_CPU_UNIQUE_ID_LEN   64
> 
> Is this fixed size actually guaranteed by AMD ?  In reading the spec
> for "GET_ID" it feels like they're intentionally not specifying a
> fixed length, pushing towards querying once and then re-trying with
> the reported buffer size:
> 
>    "If the value of the ID_LEN field is too small, an 
>     INVALID_LENGTH error is returned and the minimum 
>     required length is written to the field"
> 
> I didn't find where it says 64 bytes exactly.
> 

OK.

I'll change it to dynamically allocate the ID buffer based on the length
returned by the first query, similar to sev_get_pdh_info().

I'll remove the explicit lengths from the qapi description and the
commit message.

-Dov


>> +
>>  #define SEV_INFO_BLOCK_GUID     "00f771de-1a7e-4fcb-890e-68c77e2fb44e"
>>  typedef struct __attribute__((__packed__)) SevInfoBlock {
>>      /* SEV-ES Reset Vector Address */
>> @@ -531,11 +533,31 @@ e_free:
>>      return 1;
>>  }
>>  
>> +static int
>> +sev_get_id(int fd, guchar *id_buf, size_t id_buf_len, Error **errp)
>> +{
>> +    struct sev_user_data_get_id2 id = {
>> +        .address = (unsigned long)id_buf,
>> +        .length = id_buf_len
>> +    };
>> +    int err, r;
>> +
>> +    r = sev_platform_ioctl(fd, SEV_GET_ID2, &id, &err);
>> +    if (r < 0) {
>> +        error_setg(errp, "SEV: Failed to get ID ret=%d fw_err=%d (%s)",
>> +                   r, err, fw_error_to_str(err));
>> +        return 1;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>  static SevCapability *sev_get_capabilities(Error **errp)
>>  {
>>      SevCapability *cap = NULL;
>>      guchar *pdh_data = NULL;
>>      guchar *cert_chain_data = NULL;
>> +    guchar cpu0_id[SEV_CPU_UNIQUE_ID_LEN];
>>      size_t pdh_len = 0, cert_chain_len = 0;
>>      uint32_t ebx;
>>      int fd;
>> @@ -561,9 +583,14 @@ static SevCapability *sev_get_capabilities(Error **errp)
>>          goto out;
>>      }
>>  
>> +    if (sev_get_id(fd, cpu0_id, sizeof(cpu0_id), errp)) {
>> +        goto out;
>> +    }
>> +
>>      cap = g_new0(SevCapability, 1);
>>      cap->pdh = g_base64_encode(pdh_data, pdh_len);
>>      cap->cert_chain = g_base64_encode(cert_chain_data, cert_chain_len);
>> +    cap->cpu0_id = g_base64_encode(cpu0_id, sizeof(cpu0_id));
>>  
>>      host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL);
>>      cap->cbitpos = ebx & 0x3f;
>> -- 
>> 2.25.1
>>
> 
> Regards,
> Daniel

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