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Re: [Qemu-devel] [PATCH v2] target/i386: sev: add 'sev-max-guests' field
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2] target/i386: sev: add 'sev-max-guests' field to 'query-sev-capabilities' |
Date: |
Fri, 12 Apr 2019 10:05:23 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
On 12/04/19 09:58, Laszlo Ersek wrote:
> On 04/12/19 01:55, Singh, Brijesh wrote:
>> There are limited numbers of the SEV guests that can be run concurrently.
>> A management applications may need to know this limit so that it can place
>> SEV VMs on hosts which have suitable resources available.
>>
>> Currently, this limit is not exposed to the application. Add a new
>> 'sev-max-guest' field in the query-sev-capabilities to provide this
>> information.
>>
>> Cc: Paolo Bonzini <address@hidden>
>> Cc: Markus Armbruster <address@hidden>
>> Cc: Eric Blake <address@hidden>
>> Cc: Daniel P. Berrangé <address@hidden>
>> Cc: Laszlo Ersek <address@hidden>
>> Cc: Erik Skultety <address@hidden>
>> Cc: Tom Lendacky <address@hidden>
>> Signed-off-by: Brijesh Singh <address@hidden>
>> ---
>>
>> changes since v1:
>> - document the new field and add (since 4.1) annotation.
>>
>> qapi/target.json | 9 +++++++--
>> target/i386/sev.c | 9 +++++++--
>> 2 files changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/qapi/target.json b/qapi/target.json
>> index 1d4d54b600..8cd4fc7919 100644
>> --- a/qapi/target.json
>> +++ b/qapi/target.json
>> @@ -177,13 +177,17 @@
>> # @reduced-phys-bits: Number of physical Address bit reduction when SEV is
>> # enabled
>> #
>> +# @sev-max-guests: maximum number of concurrent SEV guest with SEV-ES
>> disabled
>> +# (since 4.1)
>> +#
>> # Since: 2.12
>> ##
>> { 'struct': 'SevCapability',
>> 'data': { 'pdh': 'str',
>> 'cert-chain': 'str',
>> 'cbitpos': 'int',
>> - 'reduced-phys-bits': 'int'},
>> + 'reduced-phys-bits': 'int',
>> + 'sev-max-guests': 'int'},
>> 'if': 'defined(TARGET_I386)' }
>>
>> ##
>> @@ -200,7 +204,8 @@
>> #
>> # -> { "execute": "query-sev-capabilities" }
>> # <- { "return": { "pdh": "8CCDD8DDD", "cert-chain": "888CCCDDDEE",
>> -# "cbitpos": 47, "reduced-phys-bits": 5}}
>> +# "cbitpos": 47, "reduced-phys-bits": 5,
>> +# "sev-max-guests" : 15}}
>
> There seems to be a superfluous space character before the colon, but I
> don't think it matters much.
>
>> #
>> ##
>> { 'command': 'query-sev-capabilities', 'returns': 'SevCapability',
>> diff --git a/target/i386/sev.c b/target/i386/sev.c
>> index cd77f6b5d4..6829586fbe 100644
>> --- a/target/i386/sev.c
>> +++ b/target/i386/sev.c
>> @@ -488,7 +488,7 @@ sev_get_capabilities(void)
>> guchar *pdh_data = NULL;
>> guchar *cert_chain_data = NULL;
>> size_t pdh_len = 0, cert_chain_len = 0;
>> - uint32_t ebx;
>> + uint32_t ebx, ecx, edx;
>> int fd;
>>
>> fd = open(DEFAULT_SEV_DEVICE, O_RDWR);
>> @@ -507,7 +507,7 @@ sev_get_capabilities(void)
>> cap->pdh = g_base64_encode(pdh_data, pdh_len);
>> cap->cert_chain = g_base64_encode(cert_chain_data, cert_chain_len);
>>
>> - host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL);
>> + host_cpuid(0x8000001F, 0, NULL, &ebx, &ecx, &edx);
>> cap->cbitpos = ebx & 0x3f;
>>
>> /*
>> @@ -516,6 +516,11 @@ sev_get_capabilities(void)
>> */
>> cap->reduced_phys_bits = 1;
>>
>> + /*
>> + * The maximum number of SEV guests with SEV-ES disabled that can run
>> + * simultaneously.
>> + */
>> + cap->sev_max_guests = ecx - edx + 1;
>> out:
>> g_free(pdh_data);
>> g_free(cert_chain_data);
>>
>
> Reviewed-by: Laszlo Ersek <address@hidden>
As mentioned in v1, I don't think a management application should need
to run QEMU in order to figure this out.
Paolo