Re: [Qemu-devel] [PATCH 2/2] WHPX: register for unrecognized MSR exits

[Paolo Bonzini]

On 19/06/2018 00:01, Justin Terry (VM) wrote:
> The issue is that the Windows Hypervisor Platform will return #GP for
> any rdmsr/wrmsr that is not a virtualized MSR in the hypervisor by
> default. A virt stack (QEMU) can override this default behavior by
> registering for MSR exits. In this configuration the virt stack will
> receive any non-virtualized MSR exit and from the hypervisors
> perspective this is now effectively handled. I could certainly list
> each MSR individually but it seems overly prone to test-matrix
> errors. For example, each kernel that I try might succeed but a
> single option difference in another kernel might fail (which was the
> case here because the 4.4 kernel is different from the 4.14+ it
> seems). But, I will make any change you see fit to handle this in the
> way QEMU prefers.
> 
> As FYI, this is the same logic that Hyper-V uses in its virt stack
> for any hypervisor exits that are not handled in the hypervisor
> itself.

If by "the same logic" you mean that Hyper-V does
read-as-zero/write-to-nowhere, then the patch is okay with a comment
that says so.

Thanks,

Paolo