git: 459fbf1c42 - main - Status/2026Q2/bhyve-cpuid.adoc: Add report

The branch main has been updated by salvadore:

URL: https://cgit.FreeBSD.org/doc/commit/?id=459fbf1c42b1bdb5cb3bea956649ba5fc5385ff4

commit 459fbf1c42b1bdb5cb3bea956649ba5fc5385ff4
Author:     Hans Rosenfeld <[email protected]>
AuthorDate: 2026-07-07 16:20:07 +0000
Commit:     Lorenzo Salvadore <[email protected]>
CommitDate: 2026-07-20 11:59:34 +0000

    Status/2026Q2/bhyve-cpuid.adoc: Add report
    
    Pull Request:   https://github.com/freebsd/freebsd-doc/pull/694
---
 .../status/report-2026-04-2026-06/bhyve-cpuid.adoc | 68 ++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/website/content/en/status/report-2026-04-2026-06/bhyve-cpuid.adoc b/website/content/en/status/report-2026-04-2026-06/bhyve-cpuid.adoc
new file mode 100644
index 0000000000..763cc9cfb8
--- /dev/null
+++ b/website/content/en/status/report-2026-04-2026-06/bhyve-cpuid.adoc
@@ -0,0 +1,68 @@
+=== Full CPUID Control for bhyve
+
+Contact: Hans Rosenfeld <[email protected]>
+
+==== Project Overview
+
+Ongoing work on this project aims to integrate the existing proof-of-concept work into FreeBSD, and to add the following usability features:
+
+- a user-friendly configuration method to override individual bits, parts or even whole CPUID functions as needed, while keeping the rest of the host CPUID information or a pre-defined CPUID configuration
+- a user-friendly configuration method for the hypervisor signature reported by bhyve
+- a set of predefined CPUID configurations based on common x86 architecture levels, perhaps also including a set of CPUID data for a few real CPU models, and a user-friendly configuration method to choose one for a VM
+
+==== Changes during the last quarter
+
+===== Extensions to the bhyve configuration syntax
+
+The existing bhyve configuration file syntax was limited to assignments to configuration nodes, which parsed into tree-structured set of nvlists internally.
+
+In order to allow a more flexible configuration using pre-defined configuration file snippets, the bhyve configuration file syntax has been augmented with two new features:
+
+- A configuration node can be appended to with the `+=` operator.
+  If a value has already been assigned to the same configuration node, the new value is appended to the old value, separated by a comma.
+- Another configuration file can be included with an `include` directive.
+  Absolute and relative paths are supported, but relative paths are understood as relative to the path of the configuration file the include directive appears in.
+
+===== Yet more flexible CPUID configuration
+
+The CPUID configuration mechanism has been extended to support symbolic feature names, where each name corresponds to a particular bit of a register for a CPUID function.
+This is particularly useful for individual instruction set extensions or other optional features that can be turned off or on at will.
+
+So instead of configuring `cpuid.0x00000001+=edx|=0x00040000`, you can now simply write `cpuid.enable+=psn`.
+There is also a corresponding option `cpuid.disable` for symbolic features.
+
+Using bit manipulation on CPUID register is of course still supported as not all CPUID features can be expressed in terms of individual feature bits.
+
+
+===== Using x86 architecture levels
+
+The x86 architecture levels are now implemented as a set of pre-defined configuration file snippets, each higher level building on top of the lower level.
+
+To illustrate this, here's what x86-64-v3.cfg looks now:
+
+-------------------
+include x86-64-v2.cfg
+cpuid.enable+=fma,movbe,osxsave,avx,f16c
+cpuid.enable+=bmi1,avx2,bmi2
+cpuid.enable+=abm
+-------------------
+
+The CPU or architecture model can be selected either by including the corresponding configuration file from `/usr/share/bhyve/cpu` in the bhyve configuration file, or it can be specified on the command line as part of the vCPU configuration: `bhyve [...] -c 16,model=x86-64-v1 [...]`
+
+===== CPUID constraints
+
+In order to prevent accidentally enabling CPUID features for a guest CPU which the host CPU doesn't support, the CPUID configuration parser has been extended with a list of CPUID constraints, which are consulted when a particular CPUID register value is set or modified.
+
+For any register in a CPUID function, a constraint can specify which bits are immutable and which may be cleared only.
+
+The constraints are checked after the CPUID configuration has been applied.
+
+
+==== Plans for next quarter
+
+* Implement overrides for CPUID constraints to ignore any constraints or to warn about violation of a constraint instead of failing VM setup.
+* Provide more pre-defined CPU configurations based on real-world CPUs.
+* Similar to setting a x86 architecture level, a mechanism will be implemented to override the hypervisor identification without requiring manually changing CPUID bits.
+* Get the whole wad reviewed and committed into FreeBSD.
+
+Sponsor: The FreeBSD Foundation