Re: [PATCH kvm-unit-tests] vmx: fixes for MAXPHYADDR requirement

[Paolo Bonzini <pbonzini@redhat.com>]

----- Original Message -----
> From: "Radim Krčmář" <rkrcmar@redhat.com>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: kvm@vger.kernel.org
> Sent: Thursday, January 25, 2018 4:11:32 PM
> Subject: Re: [PATCH kvm-unit-tests] vmx: fixes for MAXPHYADDR requirement
> 
> 2018-01-17 19:03+0100, Paolo Bonzini:
> > The EPT access tests require at least 41 bits of guest physical address
> > space.  This is because the test data needs a separate PML4 entry in the
> > EPT table.  However, many consumer-grade processors have only 36 or
> > 39-bit MAXPHYADDR, and the tests fail there with a page fault due to
> > reserved bits set in the guest (GVA->GPA) page tables.
> > 
> > Add a test on MAXPHYADDR and skip the tests if they cannot run on the
> > system under test, and only require 40 bits to lower the requirements.
> > 
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >  x86/vmx_tests.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> > index e8c97f2..0c3b5a7 100644
> > --- a/x86/vmx_tests.c
> > +++ b/x86/vmx_tests.c
> > @@ -2609,6 +2609,10 @@ static void ept_access_test_setup(void)
> >  	if (setup_ept(false))
> >  		test_skip("EPT not supported");
> >  
> > +	/* We use data->gpa = 1 << 39 so that test data has a separate pml4 entry
> > */
> > +	if (cpuid_maxphyaddr() < 40)
> 
> This does not help at the moment -- QEMU reports 40 even on hosts that
> don't have as much.  It is a QEMU bug, so applied still, thanks.

True.  However, vmx.flat is run with "-cpu host,+vmx", and that should forward
the host MAXPHYADDR, shouldn't it?

Paolo