On 10/22/2020 9:02 PM, Paolo Bonzini wrote:
On 22/10/20 03:34, Wanpeng Li wrote:
From: Wanpeng Li <wanpen...@tencent.com>

Per KVM_GET_SUPPORTED_CPUID ioctl documentation:

This ioctl returns x86 cpuid features which are supported by both the
hardware and kvm in its default configuration.

A well-behaved userspace should not set the bit if it is not supported.

Suggested-by: Jim Mattson <jmatt...@google.com>
Signed-off-by: Wanpeng Li <wanpen...@tencent.com>

It's common for userspace to copy all supported CPUID bits to
KVM_SET_CPUID2, I don't think this is the right behavior for
KVM_HINTS_REALTIME.

It reminds of X86_FEATURE_WAITPKG, which is added to supported CPUID recently as a fix but QEMU exposes it to guest only when "-overcommit cpu-pm"

(But maybe this was discussed already; if so, please point me to the
previous discussion).

Paolo


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