KVM: SVM: Enable AVIC by default for Zen4+ if x2AVIC is support

Browse source

AVIC and x2AVIC are fully functional since Zen 4, with no known hardware
errata.  Enable AVIC and x2AVIC by default on Zen4+ so long as x2AVIC is
supported (to avoid enabling partial support for APIC virtualization by
default).

Internally, convert "avic" to an integer so that KVM can identify if the
user has asked to explicitly enable or disable AVIC, i.e. so that KVM
doesn't override an explicit 'y' from the user.  Arbitrarily use -1 to
denote auto-mode, and accept the string "auto" for the module param in
addition to standard boolean values, i.e. continue to allow the user to
configure the "avic" module parameter to explicitly enable/disable AVIC.

To again maintain backward compatibility with a standard boolean param,
set KERNEL_PARAM_OPS_FL_NOARG, which tells the params infrastructure to
allow empty values for %true, i.e. to interpret a bare "avic" as "avic=y".
Take care to check for a NULL @val when looking for "auto"!

Lastly, always print "avic" as a boolean, since auto-mode is resolved
during module initialization, i.e. the user should never see "auto" in
sysfs.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Tested-by: Naveen N Rao (AMD) <naveen@kernel.org>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20250919215934.1590410-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

...

This commit is contained in:

Naveen N Rao 2025-09-19 14:59:34 -07:00 • committed by Sean Christopherson

parent b146653531

commit ca2967de5a

1 changed files with 36 additions and 4 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

40

arch/x86/kvm/svm/avic.c

View file