Re: [PATCH v2 03/15] KVM: x86/xen: Don't truncate RAX when handling hypercall from protected guest

[David Woodhouse]

On Mon, 2026-05-18 at 10:19 +0800, Binbin Wu wrote:
>  
> > > >   	longmode = is_64_bit_hypercall(vcpu);
> > > 
> > > Is the variable name misleading?
> > 
> > It most definitely is.  However, @longmode is passed around quite a few locations
> > in xen.c, and so I don't want to opportunistically fix this one variable.  Though
> > I'm definitely not opposed to a separate patch to rename them all to is_64bit or
> > something.
> 
> OK, I can do it.

This one (as shown above) is clearly indicating whether this particular
vCPU is in 64-bit mode for this particular hypercall. Changing that to
is_64bit makes sense.

However, there is a separate overall mode for the VM, which is stored
in 'kvm->arch.xen.long_mode' and accessed by userspace using the
KVM_XEN_ATTR_TYPE_LONG_MODE attribute. It affects the datatypes used by
shared memory data structures, and is also latched by the kernel when
the guest writes the MSR for the hypercall page. That one should
probably keep its name.

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