Commit 2ac44ab6 authored by Frank van der Linden's avatar Frank van der Linden Committed by Ingo Molnar
Browse files

x86/CPU/AMD: Don't force the CPB cap when running under a hypervisor

For F17h AMD CPUs, the CPB capability ('Core Performance Boost') is forcibly set,
because some versions of that chip incorrectly report that they do not have it.

However, a hypervisor may filter out the CPB capability, for good
reasons. For example, KVM currently does not emulate setting the CPB
bit in MSR_K7_HWCR, and unchecked MSR access errors will be thrown
when trying to set it as a guest:

	unchecked MSR access error: WRMSR to 0xc0010015 (tried to write 0x0000000001000011) at rIP: 0xffffffff890638f4 (native_write_msr+0x4/0x20)

	Call Trace:
	boost_set_msr+0x50/0x80 [acpi_cpufreq]

To avoid this issue, don't forcibly set the CPB capability for a CPU
when running under a hypervisor.
Signed-off-by: default avatarFrank van der Linden <>
Acked-by: default avatarBorislav Petkov <>
Cc: Andy Lutomirski <>
Cc: Linus Torvalds <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Fixes: 02371991 ("x86/CPU/AMD: Set the CPB bit unconditionally on F17h")

[ Minor edits to the changelog. ]
Signed-off-by: default avatarIngo Molnar <>
parent c3ee82ce
......@@ -824,8 +824,11 @@ static void init_amd_zn(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_ZEN);
/* Fix erratum 1076: CPB feature bit not being set in CPUID. */
if (!cpu_has(c, X86_FEATURE_CPB))
* Fix erratum 1076: CPB feature bit not being set in CPUID.
* Always set it, except when running under a hypervisor.
if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_CPB))
set_cpu_cap(c, X86_FEATURE_CPB);
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