[PATCH v2 09/29] qemu: introduce QEMU_CAPS_DEVICE_PNV_PHB3

[Ján Tomko]

On a Tuesday in 2022, Daniel Henrique Barboza wrote:
>QEMU_CAPS_DEVICE_PNV_PHB3 indicates binary support for the pnv-phb3
>device, the pcie-root controller for PowerNV8 domains, and also
>the pnv-phb3-root-port device, its pcie-root-port device.
>
>This capability is present in QEMU since 5.0.0 but these devices are
>user-creatable only after QEMU 6.2.0. This means that probing it as
>default will be misleading for users. Instead, let's use
>virQEMUCapsInitQMPVersionCaps() to check for the adequate QEMU version
>and arch and set it manually.
>
>Suggested-by: Peter Krempa <pkrempa at redhat.com>
>Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
>---
> src/qemu/qemu_capabilities.c                  | 19 +++++++++++++++++++
> src/qemu/qemu_capabilities.h                  |  1 +
> .../qemucapabilitiesdata/caps_7.0.0.ppc64.xml |  1 +
> 3 files changed, 21 insertions(+)
>
>diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
>index bb90715569..d60240912c 100644
>--- a/src/qemu/qemu_capabilities.c
>+++ b/src/qemu/qemu_capabilities.c
>@@ -662,6 +662,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
>               /* 420 */
>               "device.json+hotplug", /* QEMU_CAPS_DEVICE_JSON */
>               "hvf", /* QEMU_CAPS_HVF */
>+              "pnv-phb3", /* QEMU_CAPS_DEVICE_PNV_PHB3 */
>     );
>
>
>@@ -1397,6 +1398,17 @@ struct virQEMUCapsStringFlags virQEMUCapsObjectTypes[] = {
>     { "virtio-vga-gl", QEMU_CAPS_VIRTIO_VGA_GL },
>     { "s390-pv-guest", QEMU_CAPS_S390_PV_GUEST },
>     { "virtio-mem-pci", QEMU_CAPS_DEVICE_VIRTIO_MEM_PCI },
>+    /*
>+     * We don't probe the following PowerNV devices:
>+     *

If we don't probe them, then this comment does not belong here. Rather
it should be documented in the commit message and the place that sets it
based on the version.

>+     * { "pnv-phb3", QEMU_CAPS_DEVICE_PNV_PHB3 },
>+     * { "pnv-phb3-root-port", QEMU_CAPS_DEVICE_PNV_PHB3 },
>+     *
>+     * Because they are present in QEMU binaries since QEMU 5.0.0
>+     * but became user creatable only in the QEMU 7.0.0 development
>+     * cycle. Their respective capabilities are being set in
>+     * virQEMUCapsInitQMPVersionCaps().

Alternatively, you can probe the device here (just "pnv-phb3", no need
to look at both) and clear the capability if QEMU is too old to let the
user create it. That way it will be easier to delete years from now when
we raise minimum QEMU version.

>+     */
> };
>
>
>@@ -5231,6 +5243,13 @@ virQEMUCapsInitQMPVersionCaps(virQEMUCaps *qemuCaps)
>      */
>     if (qemuCaps->version < 5002000)
>         virQEMUCapsSet(qemuCaps, QEMU_CAPS_ENABLE_FIPS);
>+
>+    /* PowerNV pnv-phb devices weren't user creatable up to
>+     * QEMU 6.2.0. The version value set here was taken from a
>+     * binary post 6.2.0 release that has user creatable pnv-phb
>+     * support. */
>+    if (qemuCaps->version >= 6002050 && ARCH_IS_PPC64(qemuCaps->arch))

I'd rather not use the git version in here.

If nothing better, at least rewrite this to: > 6002000

Even better if we waited for 7.0.0 or QEMU had some property we could
look for (looking at QEMU history there were some properties removed
for phb4 as a part of making them user creatable but I don't see
anything for phb3).

>+        virQEMUCapsSet(qemuCaps, QEMU_CAPS_DEVICE_PNV_PHB3);
> }
>
>

With the comment removed and/or the code probing first then clearing
based on version number:

Reviewed-by: Ján Tomko <jtomko at redhat.com>

Jano
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