Re: [libvirt] [PATCH v2 2/4] qemu: caps: add QEMU_CAPS_QCOW2_L2_CACHE_SIZE
On 11/8/18 8:02 AM, Nikolay Shirokovskiy wrote:
For qemu capable of setting l2-cache-size for qcow2 images
to INT64_MAX and semantics of upper limit on l2 cache
size. We can only check this by qemu version (3.1.0) now.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy(a)virtuozzo.com>
---
src/qemu/qemu_capabilities.c | 5 +++++
src/qemu/qemu_capabilities.h | 1 +
2 files changed, 6 insertions(+)
This patch needs to be updated to top of tree.
diff --git a/src/qemu/qemu_capabilities.c
b/src/qemu/qemu_capabilities.c
index 2ca5af3..49a3b60 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -509,6 +509,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
"vfio-pci.display",
"blockdev",
"vfio-ap",
+ "qcow2.l2-cache-size",
When you do update, you will need to fix the comma-less entry for
"egl-headless.rendernode" as well, unless someone else gets to it first.
);
@@ -4117,6 +4118,10 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_PSERIES_MAX_CPU_COMPAT);
}
+ /* l2-cache-size before 3001000 does not accept INT64_MAX */
+ if (qemuCaps->version >= 3001000)
+ virQEMUCapsSet(qemuCaps, QEMU_CAPS_QCOW2_L2_CACHE_SIZE);
+
Not a fan of this.
The 'l2-cache-size' was supported since QEMU 2.2. A "newer" algorithm
for cache adjustment has been supported since QEMU 2.12 (and there's
l2-cache-entry-size that "could be used" to know that). Then there's
some unreferenced commit indicating usage of INT64_MAX. Tracking that
down, I find qemu.git commit 6c1c8d5d from Max which enforces MAX_INT.
Still does that really matter? Let QEMU pick their own max and don't
have libvirt be the arbiter of that (like I noted in my 1/4 review). My
reasoning is that there's been quite a few "adjustments" to the
algorithms along the way. Those adjustments are one of the concerns
voiced in the past why making any "semi-permanent" change to the value
in some libvirt XML format has been NACKed historically. THus by placing
boundaries that are true today we limit ourselves for the future.
BTW: If 3.1 was the "base" from which you want to work, then adjustments
to the tests/qemucapabilitiesdata/*3_1*{.replies|.xml } files would be
required as evidenced by your patch 4. The *.xml file would need to have
the correct <version>3001000</version> setting which should allow patch4
to be merged into patch3.
John
if (virQEMUCapsProbeQMPCommands(qemuCaps, mon) < 0)
goto cleanup;
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 6bb9a2c..bb2ac17 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -493,6 +493,7 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check
*/
QEMU_CAPS_VFIO_PCI_DISPLAY, /* -device vfio-pci.display */
QEMU_CAPS_BLOCKDEV, /* -blockdev and blockdev-add are supported */
QEMU_CAPS_DEVICE_VFIO_AP, /* -device vfio-ap */
+ QEMU_CAPS_QCOW2_L2_CACHE_SIZE, /* -blockdev supports l2-cache-size with INT64_MAX
value */
QEMU_CAPS_LAST /* this must always be the last item */
} virQEMUCapsFlags;