Hi,
On Fri, 2019-10-18 at 18:53 +0200, Vitaly Kuznetsov wrote:
> Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx> writes:
>
> > From: Suraj Jitindar Singh <surajjs@xxxxxxxxxx>
> >
> > The test in x86/apic.c named test_pv_ipi is used to test for a
> > kernel
> > bug where a guest making the hcall KVM_HC_SEND_IPI can trigger an
> > out of
> > bounds access.
> >
> > If the host doesn't implement this hcall then the out of bounds
> > access
> > cannot be triggered.
> >
> > Detect the case where the host doesn't implement the
> > KVM_HC_SEND_IPI
> > hcall and skip the test when this is the case, as the test doesn't
> > apply.
> >
> > Output without patch:
> > FAIL: PV IPIs testing
> >
> > With patch:
> > SKIP: PV IPIs testing: h-call not available
> >
> > Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> > ---
> > x86/apic.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/x86/apic.c b/x86/apic.c
> > index eb785c4..bd44b54 100644
> > --- a/x86/apic.c
> > +++ b/x86/apic.c
> > @@ -8,6 +8,8 @@
> > #include "atomic.h"
> > #include "fwcfg.h"
> >
> > +#include <linux/kvm_para.h>
> > +
> > #define MAX_TPR 0xf
> >
> > static void test_lapic_existence(void)
> > @@ -638,6 +640,15 @@ static void test_pv_ipi(void)
> > unsigned long a0 = 0xFFFFFFFF, a1 = 0, a2 = 0xFFFFFFFF, a3 =
> > 0x0;
> >
> > asm volatile("vmcall" : "=a"(ret) :"a"(KVM_HC_SEND_IPI),
> > "b"(a0), "c"(a1), "d"(a2), "S"(a3));
> > + /*
> > + * Detect the case where the hcall is not implemented by the
> > hypervisor and
> > + * skip this test if this is the case. Is the hcall isn't
> > implemented then
> > + * the bug that this test is trying to catch can't be
> > triggered.
> > + */
> > + if (ret == -KVM_ENOSYS) {
> > + report_skip("PV IPIs testing: h-call not available");
> > + return;
> > + }
> > report("PV IPIs testing", !ret);
> > }
>
> Should we be checking CPUID bit (KVM_FEATURE_PV_SEND_IPI) instead?
>
That's also an option. It will produce the same result.
Would that be the preferred approach or is the method used in the
current patch ok?
