----- pbonzini@xxxxxxxxxx wrote:
> On 09/01/2018 16:08, Liran Alon wrote:
> >
> > ----- pbonzini@xxxxxxxxxx wrote:
> >
> >> Results on Haswell:
> >>
> >> wr_ibrs_msr 506 (actually ~250, because the test writes
> twice)
> >> wr_ibpb_msr 4212
> >>
> >> Yuck.
> >>
> >> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >> ---
> >> lib/x86/msr.h | 3 +++
> >> x86/vmexit.c | 23 +++++++++++++++++++++++
> >> 2 files changed, 26 insertions(+)
> >>
> >> diff --git a/lib/x86/msr.h b/lib/x86/msr.h
> >> index 2c0598c..3eff710 100644
> >> --- a/lib/x86/msr.h
> >> +++ b/lib/x86/msr.h
> >> @@ -32,6 +32,9 @@
> >> #define EFER_FFXSR (1<<_EFER_FFXSR)
> >>
> >> /* Intel MSRs. Some also available on other CPUs */
> >> +#define MSR_IA32_SPEC_CTRL 0x00000048
> >> +#define MSR_IA32_PRED_CMD 0x00000049
> >> +
> >> #define MSR_IA32_PERFCTR0 0x000000c1
> >> #define MSR_IA32_PERFCTR1 0x000000c2
> >> #define MSR_FSB_FREQ 0x000000cd
> >> diff --git a/x86/vmexit.c b/x86/vmexit.c
> >> index 65111ae..a04e971 100644
> >> --- a/x86/vmexit.c
> >> +++ b/x86/vmexit.c
> >> @@ -413,6 +413,27 @@ static void tscdeadline(void)
> >> while (x == 0) barrier();
> >> }
> >>
> >> +static int has_spec_ctrl(void)
> >> +{
> >> + return !!(cpuid_indexed(7,0).d & (1 << 26));
> >> +}
> >> +
> >> +static void wr_ibrs_msr(void)
> >> +{
> >> + wrmsr(MSR_IA32_SPEC_CTRL, 1);
> >> + wrmsr(MSR_IA32_SPEC_CTRL, 0);
> >> +}
> >> +
> >> +static int has_ibpb(void)
> >> +{
> >> + return has_spec_ctrl() || !!(cpuid(0x80000008).b & (1 <<
> 12));
> >
> > Why are you doing here "has_spec_ctrl() ||" and not just checking
> "cpuid(0x80000008).b & (1 << 12)"?
>
> Because Intel's recent microcode updates do not expose
> CPUID[EAX=0x80000008].EBX[12], but they do add PRED_CMD MSR.
>
> Paolo
OK that's weird... :)
So doesn't it make sense to also have same logic in cpu_has_ibpb_support() in KVM?
Also, I would add an appropriate comment above those lines as this is not trivial.
-Liran
>
> >
> > -Liran
> >
> >> +}
> >> +
> >> +static void wr_ibpb_msr(void)
> >> +{
> >> + wrmsr(MSR_IA32_PRED_CMD, 1);
> >> +}
> >> +
> >> static struct test tests[] = {
> >> { cpuid_test, "cpuid", .parallel = 1, },
> >> { vmcall, "vmcall", .parallel = 1, },
> >> @@ -440,6 +461,8 @@ static struct test tests[] = {
> >> { ipi, "ipi", is_smp, .parallel = 0, },
> >> { ipi_halt, "ipi_halt", is_smp, .parallel = 0, },
> >> { ple_round_robin, "ple_round_robin", .parallel = 1 },
> >> + { wr_ibrs_msr, "wr_ibrs_msr", has_spec_ctrl, .parallel = 1 },
> >> + { wr_ibpb_msr, "wr_ibpb_msr", has_ibpb, .parallel = 1 },
> >> { wr_tsc_adjust_msr, "wr_tsc_adjust_msr", .parallel = 1 },
> >> { rd_tsc_adjust_msr, "rd_tsc_adjust_msr", .parallel = 1 },
> >> { NULL, "pci-mem", .parallel = 0, .next = pci_mem_next },
> >> --
> >> 1.8.3.1
