Re: [PATCH v6 05/16] target-i386: Use Hypervisor level in -machine pc,accel=kvm.

Marcelo Tosatti
2012-10-09T17:18:14Z

On Mon, Sep 24, 2012 at 10:32:07AM -0400, Don Slutz wrote:
> Also known as Paravirtualization level.
>
> This change is based on:
>
> Microsoft Hypervisor CPUID Leaves:
> http://msdn.microsoft.com/en-us/library/windows/hardware/ff542428%28v=vs.85%29.aspx
>
> Linux kernel change starts with:
> http://fixunix.com/kernel/538707-use-cpuid-communicate-hypervisor.html
> Also:
> http://lkml.indiana.edu/hypermail/linux/kernel/1205.0/00100.html
>
> VMware documention on CPUIDs (Mechanisms to determine if software is
> running in a VMware virtual machine):
> http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1009458
>
> QEMU knows this is KVM_CPUID_SIGNATURE (0x40000000).
>
> Signed-off-by: Don Slutz <Don@CloudSwitch.com>
> ---
> target-i386/kvm.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 895d848..8462c75 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -389,12 +389,12 @@ int kvm_arch_init_vcpu(CPUX86State *env)
> c = &cpuid_data.entries[cpuid_i++];
> memset(c, 0, sizeof(*c));
> c->function = KVM_CPUID_SIGNATURE
> - if (!hyperv_enabled()) {
> + if (!env->cpuid_hv_level_set) {
> memcpy(signature, "KVMKVMKVM\0\0\0", 12);
> c->eax = 0;
> } else {
> memcpy(signature, "Microsoft Hv", 12);
> - c->eax = HYPERV_CPUID_MIN;
> + c->eax = env->cpuid_hv_level;

This breaks hyperv_enabled() checks.

Don, are you certain it is worthwhile to make this configurable?
Can you explain why, under your scenario, it is worthwhile?

Because these are separate problems:

- "Fake" VMWare hypervisor (which seems to be your main goal).
- Make CPUID HV leafs configurable via command line.

My point is that the CPUIDs must be carefully constructed,
that i miss the point why making them configurable is
desired.