Considering there is Ubuntu 24.04 LTS out for more than a year that
contains all those features. And the Ubuntu kernel (for Jammy) does not
seem to have picked up the requested backports, yet.
There isn't a lot we can do on the qemu side, for now. I'm unassigning
myself.
** Changed in: qemu (Ubuntu Jammy)
Importance: Undecided => Wishlist
** Changed in: qemu (Ubuntu Jammy)
Status: Triaged => Incomplete
** Changed in: qemu (Ubuntu Jammy)
Assignee: Lukas Märdian (slyon) => (unassigned)
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https://bugs.launchpad.net/bugs/2019971
Title:
Add EPYC-Genoa model
Status in linux package in Ubuntu:
Confirmed
Status in qemu package in Ubuntu:
Fix Released
Status in linux source package in Jammy:
Confirmed
Status in qemu source package in Jammy:
Incomplete
Status in linux source package in Kinetic:
Won't Fix
Status in qemu source package in Kinetic:
Won't Fix
Status in linux source package in Lunar:
Won't Fix
Status in qemu source package in Lunar:
Won't Fix
Status in linux source package in Mantic:
Won't Fix
Status in qemu source package in Mantic:
Won't Fix
Bug description:
[Impact]
* To avoid bugs with newer Hardware and to allow users/admins to control
the KVM guests correctly we usually try to backport major CPU-
detect/control features back to at least the last LTS (currently jammy)
In SRU Terms this is under the second entry in
https://wiki.ubuntu.com/StableReleaseUpdates#Other_safe_cases
* In this particular case it is about Support for EPYC Genoa chips
https://en.wikipedia.org/wiki/Epyc#Fourth_generation_Epyc_(Genoa)
[Test Plan]
* First of all we'll (and have in advance) run general regression
tests
* Second you'd want to run this with host-model and host-passthrough on
Rome / Milan chips to ensure no case is now falling in to a totally
dysfunctional state
* Qemu shall show to be aware of the new types
# qemu-system-x86_64 -cpu ? | grep EPYC-Genoa
x86 EPYC-Genoa (alias configured by machine type)
x86 EPYC-Genoa-v1 AMD EPYC-Genoa Processor
* Finally migrations between old->new should be checked to work fine.
[Where problems could occur]
* This kind of "add the new type" usually only s a problem in backward-
migratebility which isn't supported anyway. Never the less the areas to
look out for is behavior on various AMD EPYC chips. To ensure that old
chips won't change in a breaking way (they might detect new features
now, but not more) and that new Milan chips are now all detected
properly.
[Other Info]
* This is not the first time new AMD chips need to add their definitions,
for example bug 1921880 was similar
----
QEMU added a separate model for EPYC-Genoa in
https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg02087.html
On the qemu side most bits are already present as far back as jammy. The only
things missing are the vnmi and auto-ibrs flag.
The lfence-always-serializing, amd-psfd, no-nested-data-bp, null-sel-clr-base
are part of the Milan-v2 patch set
https://github.com/qemu/qemu/commit/62a798d4bc2c3e767d94670776c77a7df274d7c5.patch
https://github.com/qemu/qemu/commit/166b1741884dd4fd7090b753cd7333868457a29b.patch
Kernel auto-ibrs et al:
https://lkml.kernel.org/lkml/[email protected]/
kvm: Add support for CPUID_80000021_EAX
*
https://github.com/torvalds/linux/commit/8415a74852d7c24795007ee9862d25feb519007c.patch
kvm: Add the NO_NESTED_DATA_BP feature
*
https://github.com/torvalds/linux/commit/a9dc9ec5a1fafc3d2fe7a7b594eefaeaccf89a6b.patch
kvm: Move X86_FEATURE_LFENCE_RDTSC to its native leaf
*
https://github.com/torvalds/linux/commit/84168ae786f8a15a7eb0f79d34f20b8d261ce2f5.patch
kvm: Add the Null Selector Clears Base feature
*
https://github.com/torvalds/linux/commit/5b909d4ae59aedc711b7a432da021be0e82c95a0.patch
kvm: Add the SMM_CTL MSR not present feature
https://github.com/torvalds/linux/commit/faabfcb194a8d0686396e3fff6a5b42911f65191.patch
x86/cpu: Support AMD Automatic IBRS
https://github.com/torvalds/linux/commit/e7862eda309ecfccc36bb5558d937ed3ace07f3f.patch
KVM: Add common feature flag for AMD's PSFD
https://github.com/torvalds/linux/commit/3d8f61bf8bcd69bcd397276d53aa18f7ca8347f9.patch
Add support for virtual NMIs
https://github.com/torvalds/linux/commit/4a5fd419952e49ef870e9259d815718062871cc1.patch
Please consider adding/backporting these.
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