Re: [PATCH v4 4/7] KVM: VMX: Implement LASS violation check

[Sean Christopherson <seanjc@google.com>]

On Tue, Sep 15, 2026, Sohil Mehta wrote:
> On 9/15/2026 7:04 AM, Sean Christopherson wrote:
> > That said, I love Sohil's idea of adding a function comment.  Someting along the
> > lines of "The basic flow is this: <example>, but the actual behavior is far more
> > subtle due to many exceptions and edge cases".
> 
> Great, how about this?

LGTM.

> > /*
> >  * Check if an access violates LASS purely based on bit 63 of the linear address
> >  * and whether the access targets the "wrong" half of the address space. The
> >  * basic flow is straightforward:
> >  *
> >  *	if (exempt from LASS)
> >  *		no violation;
> >  *	else if (user access)
> >  *		violation when address is in the supervisor half;
> >  *	else
> >  *		violation when address is in the user half;
> >  *
> >  * but the actual behavior is far more subtle due to the many exceptions and
> >  * edge cases. For example, the implementation depends on which accesses are
> >  * exempt, what constitutes a user access, and how supervisor data accesses
> >  * differ from instruction fetches.
> >  */
> > bool vmx_is_lass_violation(struct kvm_vcpu *vcpu, gva_t gva,
> > 			   unsigned int size, unsigned int flags)
> 
> 
> 
> Sean, other than this, do you want to see any big change in the series?

Dunno, I haven't looked at anything else in the series, I just saw that I got
summoned :-)

It's on my list of things to review, but I'm behind on reviews this kernel cycle
for a variety of reasons.

> The sashiko complains are false-positives. There are a couple of nits to
> be addressed, and I need to change Binbin's SoBs into Reviewed-bys.
> Otherwise, I think the series (1-5) is getting ready to be picked up.
>