linux-kernel - RE: [tip: ras/core] x86/mce: Enable additional error logging on certain Intel CPUs

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Date:   Mon, 9 Nov 2020 23:36:16 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Jim Mattson <jmattson@...gle.com>
CC:     Qian Cai <cai@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tip-commits@...r.kernel.org" 
        <linux-tip-commits@...r.kernel.org>, Boris Petkov <bp@...en8.de>,
        "Borislav Petkov" <bp@...e.de>, x86 <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: RE: [tip: ras/core] x86/mce: Enable additional error logging on
 certain Intel CPUs

> I wouldn't expect all hypervisors to necessarily set CPUID.01H:ECX[bit
> 31]. Architecturally, on Intel CPUs, that bit is simply defined as
> "not used." There is no documented contract between Intel and
> hypervisor vendors regarding the use of that bit. (AMD, on the other
> hand, *does* document that bit as "reserved for use by hypervisor to
> indicate guest status.")

Maybe no contract ... but a bunch of places (many of them in Intel
specific code) that check for it.  Perhaps I should poke the owners
of the Intel SDM to accept the inevitable.

$ git grep "boot_cpu_has(X86_FEATURE_HYPERVISOR"
arch/x86/events/core.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/events/intel/core.c:   if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/events/intel/core.c:           int assume = 3 * !boot_cpu_has(X86_FEATURE_HYPERVISOR);
arch/x86/events/intel/cstate.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/events/intel/uncore.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/apic/apic.c:    if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/bugs.c:     if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/bugs.c:     else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/bugs.c:     if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/kernel/cpu/bugs.c:     if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/kernel/cpu/intel.c:    if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/mshyperv.c: if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/vmware.c: * If !boot_cpu_has(X86_FEATURE_HYPERVISOR), vmware_hypercall_mode
arch/x86/kernel/cpu/vmware.c:   if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/kernel/jailhouse.c:        !boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/kvm.c:  if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/paravirt.c:     if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/tsc.c:  if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
arch/x86/mm/init_64.c:  if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
drivers/acpi/processor_idle.c:  if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h:       return boot_cpu_has(X86_FEATURE_HYPERVISOR);
drivers/gpu/drm/i915/i915_memcpy.c:         !boot_cpu_has(X86_FEATURE_HYPERVISOR))
drivers/gpu/drm/radeon/radeon_device.c: return boot_cpu_has(X86_FEATURE_HYPERVISOR);
drivers/visorbus/visorchipset.c:        if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {

-Tony