From: Frank van der Linden fllinden@amazon.com
[ Upstream commit 2ac44ab608705948564791ce1d15d43ba81a1e38 ]
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] cpuhp_invoke_callback+0x86/0x560 sort_range+0x20/0x20 cpuhp_thread_fun+0xb0/0x110 smpboot_thread_fn+0xef/0x160 kthread+0x113/0x130 kthread_create_worker_on_cpu+0x70/0x70 ret_from_fork+0x35/0x40
To avoid this issue, don't forcibly set the CPB capability for a CPU when running under a hypervisor.
Signed-off-by: Frank van der Linden fllinden@amazon.com Acked-by: Borislav Petkov bp@suse.de Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: bp@alien8.de Cc: jiaxun.yang@flygoat.com Fixes: 0237199186e7 ("x86/CPU/AMD: Set the CPB bit unconditionally on F17h") Link: http://lkml.kernel.org/r/20190522221745.GA15789@dev-dsk-fllinden-2c-c1893d73... [ Minor edits to the changelog. ] Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/cpu/amd.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index be6d0543e626..52a65f14db06 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -766,8 +766,11 @@ 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); }