On Mon, 2024-03-18 at 14:34 -0700, Sean Christopherson wrote: > On Mon, Mar 18, 2024, David Woodhouse wrote: > > > > /* Either gpa or uhva must be valid, but not both */ > > if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) == kvm_is_error_hva(uhva))) > > return -EINVAL; > > > > Hm, that comment doesn't match the code. It says "not both", but the > > code also catches the "neither" case. I think the gpa is in %rbx and > > uhva is in %r12, so this is indeed the 'neither' case. > > > > Is it expected that we can end up with a cache marked active, but with > > the address not valid? Maybe through a race condition with deactive? or > > more likely than that? > > It's the darn PV system time MSR, which allows the guest to triggering activation > with any GPA value. That results in the cache being marked active without KVM > ever setting the GPA (or any other fields). The fix I'm testing is to move the > offset+len check up into activate() and refresh(). Not sure I even want a gpc of length 1 to work at INVALID_GPA; I don't think it's the offset+length check we want to be looking at? If we've activated the gpc with gpa==INVALID_GPA, surely the right thing to do is just let it fail (perhaps with an explicit check or just letting the memslot lookup fail). After fixing that WARN_ON be if (WARN_ON_ONCE(!kvm_is_error_gpa(gpa) && !kvm_is_error_hva(uhva)))
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