Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] kvm/x86: reserve bit KVM_HINTS_PHYS_ADDRESS_SIZE_DATA_VALID | Date | Tue, 13 Sep 2022 11:40:30 +0200 |
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Sean Christopherson <seanjc@google.com> writes:
> On Fri, Sep 09, 2022, Vitaly Kuznetsov wrote:
...
>> While this certainly looks like an overkill here, we could probably add >> new, VMM-spefific CPUID leaves to KVM, e.g. >> >> 0x4000000A: VMM signature >> 0x4000000B: VMM features >> 0x4000000C: VMM quirks >> ... >> >> this way VMMs (like QEMU) could identify themselves and suggest VMM >> specific things to guests without KVM's involvement. Just if 'fw_cfg' is >> not enough) > > I don't think KVM needs to get involved in that either. The de facto hypervisor > CPUID standard already allows for multiple hypervisors/VMMs to announce themselves > to the guest, e.g. QEMU could add itself as another VMM using 0x40000100 (shifted > as necessary to accomodate KVM+Hyper-V).
True, VMM can just use another hypervisor space (+0x100) but we can view it from a slightly different angle: KVM itself is insufficient to run VMs, there's always a VMM in the background, we may want to provide a "standard" for its information meaning guests won't need to search for VMMs signature[s] but can directly refer to "standardized" leaves.
(All this is a purely theoretical discussion at this point, we need a good reason to introduce this first).
-- Vitaly
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