| Message ID | 20180226213019.GE9497@char.us.oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 26/02/2018 22:30, Konrad Rzeszutek Wilk wrote: > On Mon, Feb 26, 2018 at 03:51:30PM -0500, Konrad Rzeszutek Wilk wrote: >> On Mon, Feb 26, 2018 at 08:37:11PM +0100, Borislav Petkov wrote: >>> On Mon, Feb 26, 2018 at 09:39:12AM -0500, Konrad Rzeszutek Wilk wrote: >>>> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c >>>> index d19e903214b4..87d044ce837f 100644 >>>> --- a/arch/x86/kernel/cpu/intel.c >>>> +++ b/arch/x86/kernel/cpu/intel.c >>>> @@ -144,6 +144,13 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c) >>>> { >>>> int i; >>>> >>>> + /* >>>> + * We know that the hypervisor lie to us on the microcode version so >>>> + * we may as well trust that it is running the correct version. >>>> + */ >>>> + if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) >>> >>> I guess >>> >>> cpu_has(c, X86_FEATURE_HYPERVISOR) >>> >>> since we're passing a ptr to the current CPU. >> >> Ah yes. Let me fix it up and repost. > > I've posted it (but I can't seem to find it on LKML). Here it is in this > thread. Also adding ingo + tglrx > > From 6abac2ccf105d57d60c094950e32139e435cbefe Mon Sep 17 00:00:00 2001 > From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Date: Mon, 26 Feb 2018 09:35:01 -0500 > Subject: [PATCH v2] x86/spectre_v2: Don't check bad microcode versions when > running under hypervisors. > > As: > 1) We know they lie about the env anyhow (host mismatch) > 2) Even if the hypervisor (Xen, KVM, VMWare, etc) provided > a valid "correct" value, it all gets to be very murky > when migration happens (do you provide the "new" > microcode of the machine?). > > And in reality the cloud vendors are the ones that should make > sure that the microcode that is running is correct and we should > just sing lalalala and trust them. > > CC: stable@vger.kernel.org > CC: Ingo Molnar <mingo@redhat.com> > CC: "H. Peter Anvin" <hpa@zytor.com> > CC: x86@kernel.org > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Cc: Andi Kleen <ak@linux.intel.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Masami Hiramatsu <mhiramat@kernel.org> > Cc: Arjan van de Ven <arjan@linux.intel.com> > Cc: David Woodhouse <dwmw@amazon.co.uk> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > > --- > v2: Change comments to be more in line with the state of the world. > v3: Use cpu_has instead of boot_cpu_has per Borislav's review. Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kernel/cpu/intel.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > index d19e903214b4..4aa9fd379390 100644 > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -144,6 +144,13 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c) > { > int i; > > + /* > + * We know that the hypervisor lie to us on the microcode version so > + * we may as well hope that it is running the correct version. > + */ > + if (cpu_has(c, X86_FEATURE_HYPERVISOR)) > + return false; > + > for (i = 0; i < ARRAY_SIZE(spectre_bad_microcodes); i++) { > if (c->x86_model == spectre_bad_microcodes[i].model && > c->x86_stepping == spectre_bad_microcodes[i].stepping) >
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index d19e903214b4..4aa9fd379390 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -144,6 +144,13 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c) { int i; + /* + * We know that the hypervisor lie to us on the microcode version so + * we may as well hope that it is running the correct version. + */ + if (cpu_has(c, X86_FEATURE_HYPERVISOR)) + return false; + for (i = 0; i < ARRAY_SIZE(spectre_bad_microcodes); i++) { if (c->x86_model == spectre_bad_microcodes[i].model && c->x86_stepping == spectre_bad_microcodes[i].stepping)