[libvirt] [PATCH 0/7] qemu: use domCaps for validation

[Daniel Henrique Barboza]

Tried the patch series. Unfortunately I didn't get the <rng> element
reported in virsh capabilities, however I am not sure if this hardware
(Lenovo T480) has a hardware RNG device to report anyways. I'll check
it later when I have the chance.

It is worth noticing that patch 3 is conflicting with current master. Extra
code in qemu_driver.c that shifted the lines that the patch is changing
(trivial) and, in qemu_conf.c, I had to change the call to
virQEMUCapsFillDomainCaps since it is now taking an extra argument
(added by 5b9819eedc). This change was enough to get the patch rolling:


+++ b/src/qemu/qemu_conf.c
@@ -1424,6 +1424,7 @@ 
virQEMUDriverGetDomainCapabilities(virQEMUDriverPtr driver,
              goto cleanup;

          if (virQEMUCapsFillDomainCaps(caps, domCaps, qemuCaps,
+                                      driver->privileged,
                                        cfg->firmwares, cfg->nfirmwares) 
< 0)
              goto cleanup;



Thanks,


DHB

On 4/4/19 8:37 PM, Cole Robinson wrote:
> I'm trying to remove some hurdles and pitfalls WRT extending
> domaincapabilities data. One issue is that it's too easy to add
> invalid data to it, or let the data become out of date.
>
> For example the first two patches of this series add <rng model=X>
> domcaps reporting. The logic to fill in the domcaps data from qemuCaps
> is nearly identical to the logic we use to validate rng->model in
> qemuDomainRNGDefValidate. If just those patches are added, and later
> a new qemu rng model was introduced, a future patch could easily
> miss updated domaincapabilities output.
>
> This series aims to set up a pattern to prevent these types of issues
> from sneaking in. A function virDomainCapsDeviceDefValidate is added
> which will use domcaps data to perform validation against a devicedef.
> The existing qemu <rng> model validation is moved there. This ensures
> that any future <rng> model additions, if they want to work in the
> qemu driver, effectively need to extend domaincapabilities as well.
> It's also theoretically useful for other drivers too.
>
> One issue is that at DomainDefValidate time we don't have domCaps
> handy, or any cache layer for domCaps assembling. Patch #4 adds
> a domCapsCache hashtable to the virQEMUCaps class for caching domCaps
> builds based on the full tuple of emulator+machine+arch+virttype.
> If qemuCaps need to be regenerated, the domCaps cache is wiped out
> for us so we don't need to worry about the data being stale, it's
> tied to the lifetime of a qemuCaps instance.
>
> Cole Robinson (7):
>    conf: domcaps: Report device <rng>
>    qemu: capabilities: fill in domcaps <rng>
>    qemu: conf: add virQEMUDriverGetDomainCapabilities
>    qemu: conf: Cache domCaps in qemuCaps
>    conf: domcaps: Add virDomainCapsDeviceDefValidate
>    qemu: domain: Call virDomainCapsDeviceDefValidate
>    qemu: Move rng model validation to domcaps
>
>   docs/formatdomaincaps.html.in                 | 35 ++++++++
>   docs/schemas/domaincaps.rng                   | 10 +++
>   src/conf/domain_capabilities.c                | 83 ++++++++++++++++++
>   src/conf/domain_capabilities.h                | 14 ++++
>   src/libvirt_private.syms                      |  1 +
>   src/qemu/qemu_capabilities.c                  | 41 +++++++++
>   src/qemu/qemu_capabilities.h                  |  1 +
>   src/qemu/qemu_conf.c                          | 84 +++++++++++++++++++
>   src/qemu/qemu_conf.h                          |  7 ++
>   src/qemu/qemu_domain.c                        | 38 +++------
>   src/qemu/qemu_driver.c                        | 18 +---
>   .../qemu_1.7.0.x86_64.xml                     |  9 ++
>   .../qemu_2.12.0-virt.aarch64.xml              | 11 +++
>   .../qemu_2.12.0.ppc64.xml                     | 11 +++
>   .../qemu_2.12.0.s390x.xml                     | 11 +++
>   .../qemu_2.12.0.x86_64.xml                    | 11 +++
>   .../qemu_2.6.0-virt.aarch64.xml               | 11 +++
>   .../qemu_2.6.0.aarch64.xml                    | 11 +++
>   .../domaincapsschemadata/qemu_2.6.0.ppc64.xml | 11 +++
>   .../qemu_2.6.0.x86_64.xml                     | 11 +++
>   .../domaincapsschemadata/qemu_2.7.0.s390x.xml | 11 +++
>   .../qemu_2.8.0-tcg.x86_64.xml                 | 11 +++
>   .../domaincapsschemadata/qemu_2.8.0.s390x.xml | 11 +++
>   .../qemu_2.8.0.x86_64.xml                     | 11 +++
>   .../qemu_2.9.0-q35.x86_64.xml                 | 11 +++
>   .../qemu_2.9.0-tcg.x86_64.xml                 | 11 +++
>   .../qemu_2.9.0.x86_64.xml                     | 11 +++
>   .../domaincapsschemadata/qemu_3.0.0.s390x.xml | 11 +++
>   .../qemu_4.0.0.x86_64.xml                     | 11 +++
>   29 files changed, 488 insertions(+), 40 deletions(-)
>

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