On Thu, Jun 26, 2025, Konrad Rzeszutek Wilk wrote: > On Thu, Jun 26, 2025 at 07:02:00AM -0700, Sean Christopherson wrote: > > And it's not like KVM is forcing userspace to enumerate support for > > ARCH_CAPABILITIES, e.g. QEMU's named AMD configs don't enumerate support. So > > while I completely agree KVM's behavior is odd and annoying for userspace to deal > > with, this is probably something that should be addressed in userspace. > > If you do -cpu host we tack this on all the time. Yes, I know. > Or you saying we should have QEMU disable this for AMD CPUs all the time? Maybe not _all_ the time. But yes, I'm suggesting that QEMU clear ARCH_CAPABILITIES when running on AMD. > Which in effect is the same thing as doing this patch.. but just moving > it to QEMU, kvm-tool, Google Cloud user-space thingie, AWS cloud thingie. I don't think kvm-tool supports Windows, and I highly doubt any cloud provider is doing the equivalent of QEMU's `-cpu host`. I.e. I suspect QEMU is the only VMM that's actually affected by this. > That is a lot more complexity than doing it in the kernel. I have a hard time believing it'd be more complex. More code, probably. But this isn't all that complex.
