On 4/2/18 6:04 PM, John Ferlan wrote:
>
> On 04/02/2018 10:18 AM, Brijesh Singh wrote:
>> QEMU >= 2.12 provides 'sev-guest' object which is used to launch encrypted
>> VMs on AMD platform using SEV feature. The various inputs required to
>> launch SEV guest is provided through the <launch-security> tag. A typical
>> SEV guest launch command line looks like this:
>>
>> # $QEMU ...\
>> -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=5 ...\
>> -machine memory-encryption=sev0 \
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
>> ---
>> src/qemu/qemu_command.c | 35 +++++++++++++++++++++++++++++
>> src/qemu/qemu_process.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 93 insertions(+)
>>
> (slight delay for next part of review - today was rocket launch day and
> then we headed out for a bit ;-))
>
>> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>> index 682d714..55bbfa2 100644
>> --- a/src/qemu/qemu_command.c
>> +++ b/src/qemu/qemu_command.c
>> @@ -7405,6 +7405,9 @@ qemuBuildMachineCommandLine(virCommandPtr cmd,
>> virQEMUCapsGet(qemuCaps, QEMU_CAPS_LOADPARM))
>> qemuAppendLoadparmMachineParm(&buf, def);
>>
>> + if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_SEV_GUEST) && def->sev)
> Since we already checked sev-guest at prepare host storage (mostly
> unconditionally), I don't think we have to make the check here as well -
> although I could be wrong...
Yes, probably we can avoid the SEV_GUEST cap check in this case. I will
make the changes in next rev.
>> + virBufferAddLit(&buf, ",memory-encryption=sev0");
>> +
>> virCommandAddArgBuffer(cmd, &buf);
>> }
>>
>> @@ -9750,6 +9753,35 @@ qemuBuildTPMCommandLine(virCommandPtr cmd,
>> return 0;
>> }
>>
>> +static void
> This probably should be an int...
I think it will be unlikely that this function will fail hence I was
using void. The only time it can fail is when we fail to create a
dh-cert and session blob file (e.g disk is full). I will propagate the
error.
>> +qemuBuildSevCommandLine(virDomainObjPtr vm, virCommandPtr cmd,
>> + virDomainSevDefPtr sev)
>> +{
>> + virBuffer obj = VIR_BUFFER_INITIALIZER;
>> + qemuDomainObjPrivatePtr priv = vm->privateData;
>> + char *path = NULL;
>> +
> if (!dev->sev)
> return 0;
>
> again, since prepare host storage checked the sev-guest capability we
> should be good to go here...
OK.
>> + VIR_DEBUG("policy=0x%x cbitpos=%d reduced_phys_bits=%d",
>> + sev->policy, sev->cbitpos, sev->reduced_phys_bits);
>> +
>> + virBufferAsprintf(&obj, "sev-guest,id=sev0,cbitpos=%d", sev->cbitpos);
>> + virBufferAsprintf(&obj, ",reduced-phys-bits=%d", sev->reduced_phys_bits);
>> + virBufferAsprintf(&obj, ",policy=0x%x", sev->policy);
> Here I would say:
>
> if (sev->policy > 0)
> virBufferAsprintf(&obj, ",policy=0x%x", sev->policy);
>
> and let qemu pick the default (which is 0x1 as I read that code).
OK, then I will remove the comment from html about the default value
since I was trying to not depend on QEMU default.
>> +
>> + if (sev->dh_cert) {
>> + ignore_value(virAsprintf(&path, "%s/dh_cert.base64", priv->libDir));
>> + virBufferAsprintf(&obj, ",dh-cert-file=%s", path);
>> + VIR_FREE(path);
>> + }
>> +
>> + if (sev->session) {
>> + ignore_value(virAsprintf(&path, "%s/session.base64", priv->libDir));
>> + virBufferAsprintf(&obj, ",session-file=%s", path);
>> + VIR_FREE(path);
>> + }
> ...since I don't believe we can ignore_value on the paths - especially
> since we're using it to create a path to a file containing some sort of
> session info or DH key (base64 encrypted).
Sure, will do.
>> +
>> + virCommandAddArgList(cmd, "-object", virBufferContentAndReset(&obj), NULL);
>> +}
>>
>> static int
>> qemuBuildVMCoreInfoCommandLine(virCommandPtr cmd,
>> @@ -10195,6 +10227,9 @@ qemuBuildCommandLine(virQEMUDriverPtr driver,
>> if (qemuBuildVMCoreInfoCommandLine(cmd, def, qemuCaps) < 0)
>> goto error;
>>
>> + if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_SEV_GUEST) && def->sev)
>> + qemuBuildSevCommandLine(vm, cmd, def->sev);
>> +
> I think we're save to change this to:
>
> if (qemuBuildSevCommandLine(vm, cmd, dev->sev) < 0)
> goto error;
>
Yep
>> if (snapshot)
>> virCommandAddArgList(cmd, "-loadvm", snapshot->def->name, NULL);
>>
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index c0105c8..0c93f15 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>> @@ -5745,6 +5745,61 @@ qemuProcessPrepareDomain(virQEMUDriverPtr driver,
>> return ret;
>> }
>>
> Two blank lines
>
>> +static int
>> +qemuBuildSevCreateFile(const char *configDir, const char *name,
>> + const char *data)
> 3 lines for args
>
>> +{
>> + char *configFile;
>> +
>> + if (!(configFile = virFileBuildPath(configDir, name, ".base64")))
>> + return -1;
>> +
>> + if (virFileRewriteStr(configFile, S_IRUSR | S_IWUSR, data) < 0) {
>> + virReportSystemError(errno, _("failed to write data to config '%s'"),
>> + configFile);
>> + goto error;
>> + }
> Check out storageBackendCreateQemuImgSecretPath which just goes straight
> to safewrite when writing to the file or qemuDomainWriteMasterKeyFile
> which is a similar w/r/t a single key file for the domain.
>
> The one thing to think about being the privileges for the file being
> created and written and the expectations for QEMU's usage. I think this
> is more like the storage secret code, but I could be wrong!
The data is public in this case, we do not need to protect it with
secret. Hence I am keeping all this certificate keys in unsecure place.
>> +
>> + VIR_FREE(configFile);
>> + return 0;
>> +
>> + error:
>> + VIR_FREE(configFile);
>> + return -1;
>> +}
>> +
> 2 blank lines
>
>> +static int
>> +qemuProcessPrepareSevGuestInput(virDomainObjPtr vm)
>> +{
>> + qemuDomainObjPrivatePtr priv = vm->privateData;
>> + virDomainDefPtr def = vm->def;
>> + virQEMUCapsPtr qemuCaps = priv->qemuCaps;
>> + virDomainSevDefPtr sev = def->sev;
>> +
>> + if (!sev)
>> + return 0;
>> +
>> + VIR_DEBUG("Prepare SEV guest");
>> +
>> + if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_SEV_GUEST)) {
>> + virReportError(VIR_ERR_INTERNAL_ERROR,
>> + _("Domain %s asked for 'sev' launch but "
> s/but/but this/
Noted.
>
>> + "QEMU does not support SEV feature"), vm->def->name);
>> + return -1;
>> + }
> Since we check for this here - I think this should be good enough for
> command line building. That is - qemuProcessPrepareHostStorage will
> come before command line building - so the check is already made.
>
Got it.
>> +
>> + if (sev->dh_cert) {
>> + if (qemuBuildSevCreateFile(priv->libDir, "dh_cert", sev->dh_cert) < 0)
>> + return -1;
>> + }
>> +
>> + if (sev->session) {
>> + if (qemuBuildSevCreateFile(priv->libDir, "session", sev->session) < 0)
>> + return -1;
>> + }
>> +
>> + return 0;
>> +}
> 2 blank lines
>
> John
>
>>
>> static int
>> qemuProcessPrepareHostStorage(virQEMUDriverPtr driver,
>> @@ -5870,6 +5925,9 @@ qemuProcessPrepareHost(virQEMUDriverPtr driver,
>> if (qemuProcessPrepareHostStorage(driver, vm, flags) < 0)
>> goto cleanup;
>>
>> + if (qemuProcessPrepareSevGuestInput(vm) < 0)
>> + goto cleanup;
>> +
>> ret = 0;
>> cleanup:
>> virObjectUnref(cfg);
>>
--
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