On Tue, Apr 28, 2026, Tycho Andersen wrote: > On Mon, Apr 27, 2026 at 02:20:10PM -0700, Sean Christopherson wrote: > > On Mon, Apr 27, 2026, Tycho Andersen wrote: > > > From: "Tycho Andersen (AMD)" <[email protected]> > > > > > > Add a user-visible way to set the RAPL_DIS bit for SNP init. > > > > > > Since setting RAPL_DIS affects the whole system, put the module parameter > > > in kvm_amd instead of in the CCP driver to hopefully make it more obvious > > > to admins. > > > > > > Signed-off-by: Tycho Andersen (AMD) <[email protected]> > > > --- > > > Documentation/admin-guide/kernel-parameters.txt | 5 +++++ > > > arch/x86/kvm/svm/sev.c | 8 ++++++++ > > > 2 files changed, 13 insertions(+) > > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > > > b/Documentation/admin-guide/kernel-parameters.txt > > > index 4d0f545fb3ec..2b50eed8664c 100644 > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > > @@ -3207,6 +3207,11 @@ Kernel parameters > > > max_snp_asid == min_sev_asid-1, will effectively make > > > SEV-ES unusable. > > > > > > + kvm-amd.rapl_disable= [KVM,AMD] Whether to disable RAPL > > > + (Running Average Power Limit) when initializing the SNP > > > + firmware. This disables the counters for the entire > > > system until an > > > + SNP shutdown command is issued. > > > > I'm pretty sure I said this earlier: KVM absolutely should not be able to > > disable > > RAPL for the entire system. That needs to be a power management thing. > > You definitely noted "not CCP", I don't think I quite understood what > that meant though: > https://lore.kernel.org/all/[email protected]/ > > I'm a little worried that putting it in power management will generate > some weird dependencies, or weakref symbols that can't change things > if they are loaded independently of kvm_amd or something. But let me > see what I can come up with.
Ugh, and it's not even powerman per se, it's actually a module in perf. Oof. I 100% agree it'll be tricky, but I also stand by comments that neither the CCP driver or KVM should be allowed to silently pull the rug out from under the RAPL module. > > KVM then needs to communicate (and enforce?) the policy to > > userspace. > > KVM doesn't need to enforce anything, the SEV firmware will generate a > launch error for policy violation if it's not supported. > > For communicating to userspace if it's not a kvm module parameter, one > option is to mask it off in sev_get_snp_supported_policy() if it was > initialized without the support. Then it'll be visible via > KVM_X86_SNP_POLICY_BITS. Ya, this is what I was envisioning.
