linux-kernel - Re: [PATCH] KVM: selftests: Ignore KVM 5-level paging support for VM_MODE_PXXV48

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Message-ID: <20200608181658.GD8223@linux.intel.com>
Date:   Mon, 8 Jun 2020 11:16:58 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sergio Perez Gonzalez <sergio.perez.gonzalez@...el.com>,
        Adriana Cervantes Jimenez <adriana.cervantes.jimenez@...el.com>,
        Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH] KVM: selftests: Ignore KVM 5-level paging support for
 VM_MODE_PXXV48_4K

On Thu, May 28, 2020 at 01:55:44PM +0200, Paolo Bonzini wrote:
> On 28/05/20 04:15, Sean Christopherson wrote:
> > Explicitly set the VA width to 48 bits for the x86_64-only PXXV48_4K VM
> > mode instead of asserting the guest VA width is 48 bits.  The fact that
> > KVM supports 5-level paging is irrelevant unless the selftests opt-in to
> > 5-level paging by setting CR4.LA57 for the guest.  The overzealous
> > assert prevents running the selftests on a kernel with 5-level paging
> > enabled.
> > 
> > Incorporate LA57 into the assert instead of removing the assert entirely
> > as a sanity check of KVM's CPUID output.
> > 
> > Fixes: 567a9f1e9deb ("KVM: selftests: Introduce VM_MODE_PXXV48_4K")
> > Reported-by: Sergio Perez Gonzalez <sergio.perez.gonzalez@...el.com>
> > Cc: Adriana Cervantes Jimenez <adriana.cervantes.jimenez@...el.com>
> > Cc: Peter Xu <peterx@...hat.com>
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> > ---
> >  tools/testing/selftests/kvm/lib/kvm_util.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> > index c9cede5c7d0de..74776ee228f2d 100644
> > --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> > @@ -195,11 +195,18 @@ struct kvm_vm *_vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
> >  	case VM_MODE_PXXV48_4K:
> >  #ifdef __x86_64__
> >  		kvm_get_cpu_address_width(&vm->pa_bits, &vm->va_bits);
> > -		TEST_ASSERT(vm->va_bits == 48, "Linear address width "
> > -			    "(%d bits) not supported", vm->va_bits);
> > +		/*
> > +		 * Ignore KVM support for 5-level paging (vm->va_bits == 57),
> > +		 * it doesn't take effect unless a CR4.LA57 is set, which it
> > +		 * isn't for this VM_MODE.
> > +		 */
> > +		TEST_ASSERT(vm->va_bits == 48 || vm->va_bits == 57,
> > +			    "Linear address width (%d bits) not supported",
> > +			    vm->va_bits);
> >  		pr_debug("Guest physical address width detected: %d\n",
> >  			 vm->pa_bits);
> >  		vm->pgtable_levels = 4;
> > +		vm->va_bits = 48;
> >  #else
> >  		TEST_FAIL("VM_MODE_PXXV48_4K not supported on non-x86 platforms");
> >  #endif
> > 
> 
> Queued, thnaks.
> 
> Paolo

Looks like this one also got lost in the 5.7 -> 5.8 transition.