Siddharth Chandrasekaran <sidcha@xxxxxxxxx> writes: > On Thu, Apr 08, 2021 at 04:30:18PM +0000, Wei Liu wrote: >> On Thu, Apr 08, 2021 at 05:54:43PM +0200, Siddharth Chandrasekaran wrote: >> > On Thu, Apr 08, 2021 at 05:48:19PM +0200, Paolo Bonzini wrote: >> > > On 08/04/21 17:40, Siddharth Chandrasekaran wrote: >> > > > > > > Although the Hyper-v TLFS mentions that a guest cannot use this feature >> > > > > > > unless the hypervisor advertises support for it, some hypercalls which >> > > > > > > we plan on upstreaming in future uses them anyway. >> > > > > > No, please don't do this. Check the feature bit(s) before you issue >> > > > > > hypercalls which rely on the extended interface. >> > > > > Perhaps Siddharth should clarify this, but I read it as Hyper-V being >> > > > > buggy and using XMM arguments unconditionally. >> > > > The guest is at fault here as it expects Hyper-V to consume arguments >> > > > from XMM registers for certain hypercalls (that we are working) even if >> > > > we didn't expose the feature via CPUID bits. >> > > >> > > What guest is that? >> > >> > It is a Windows Server 2016. >> >> Can you be more specific? Are you implementing some hypercalls from >> TLFS? If so, which ones? > > Yes all of them are from TLFS. We are implementing VSM and there are a > bunch of hypercalls that we have implemented to manage VTL switches, > memory protection and virtual interrupts. Wow, sounds awesome! Do you plan to upstream this work? > The following 3 hypercalls that use the XMM fast hypercalls are relevant > to this patch set: > > HvCallModifyVtlProtectionMask > HvGetVpRegisters > HvSetVpRegisters It seems AccessVSM and AccessVpRegisters privilges have implicit dependency on XMM input/output. This will need to be enforced in KVM userspace. -- Vitaly
