On 12/18/17 16:36 -0200, Eduardo Habkost wrote:
> On Tue, Dec 12, 2017 at 04:35:24PM +0800, Haozhong Zhang wrote:
> > Intel VMX cannot intercept guest clwb and clflushopt. When clwb and
> > clflushopt are not exposed in guest cpuid, clwb and clflushopt
> > instructions in this test case can still succeed without #UD on the
> > host CPU which has clwb and clflushopt support, though failures with
> > UD are expected.
> >
> > In order to avoid false alarms in such cases, introduce the following
> > two arguments "has_clwb" and "has_clflushopt" to allow users to
> > specify whether clwb and clflushopt are supported on the host CPU.
> >
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
> > ---
> > x86/memory.c | 29 +++++++++++++++++++++++++++--
> > 1 file changed, 27 insertions(+), 2 deletions(-)
> >
> > diff --git a/x86/memory.c b/x86/memory.c
> > index cd1eb46..03ff7d3 100644
> > --- a/x86/memory.c
> > +++ b/x86/memory.c
> > @@ -23,10 +23,29 @@ static void handle_ud(struct ex_regs *regs)
> > regs->rip += isize;
> > }
> >
> > +/*
> > + * Intel VMX cannot intercept guest clwb and clflushopt. When clwb and
> > + * clflushopt are not exposed in guest cpuid, clwb and clflushopt
> > + * instructions in this test case can still succeed without #UD on
> > + * the host CPU which has clwb and clflushopt support. In order to avoid
> > + * false alarms in such cases, introduce the following two arguments
> > + * to allow users to specify whether clwb and clflushopt are supported on
> > + * the host CPU:
> > + * - has_clwb: indicates clwb is supported on the host CPU
> > + * - has_clflushopt: indicates clflushopt is supported on the host CPU
> > + */
>
> Why not simply use "-cpu host" to make sure the guest CPUID flags
> match host CPUID?
>
Can I understand that testing these two cases with host/guest CPUID
mismatch (specially clwb and clflushopt flags) is invalid? If yes,
please ignore this patch.
Thanks,
Haozhong
>
> > int main(int ac, char **av)
> > {
> > struct cpuid cpuid7, cpuid1;
> > int xfail;
> > + int host_has_clwb = 0, host_has_clflushopt = 0; /* 0: unknown */
> > + int i;
> > +
> > + for (i = 1; i < ac; i++)
> > + if (!strcmp(av[i], "has_clwb"))
> > + host_has_clwb = 1;
> > + else if (!strcmp(av[i], "has_clflushopt"))
> > + host_has_clflushopt = 1;
> >
> > setup_idt();
> > handle_exception(UD_VECTOR, handle_ud);
> > @@ -63,13 +82,19 @@ int main(int ac, char **av)
> > ud = 0;
> > /* clflushopt (%rbx): */
> > asm volatile(".byte 0x66, 0x0f, 0xae, 0x3b" : : "b" (&target));
> > - report_xfail("clflushopt", xfail, ud == 0);
> > + if (host_has_clflushopt)
> > + report("clflushopt", ud == 0);
> > + else
> > + report_xfail("clflushopt", xfail, ud == 0);
> >
> > xfail = !(cpuid7.b & (1U << 24)); /* CLWB */
> > ud = 0;
> > /* clwb (%rbx): */
> > asm volatile(".byte 0x66, 0x0f, 0xae, 0x33" : : "b" (&target));
> > - report_xfail("clwb", xfail, ud == 0);
> > + if (host_has_clwb)
> > + report("clwb", ud == 0);
> > + else
> > + report_xfail("clwb", xfail, ud == 0);
> >
> > ud = 0;
> > /* clwb requires a memory operand, the following is NOT a valid
> > --
> > 2.14.1
> >
>
> --
> Eduardo
