releases/4.19.54/x86-cpu-amd-don-t-force-the-cpb-cap-when-running-und.patch

   1 From 5787b250603accfa2870606eb63628b9a252b324 Mon Sep 17 00:00:00 2001
   2 From: Frank van der Linden <fllinden@amazon.com>
   3 Date: Wed, 22 May 2019 22:17:45 +0000
   4 Subject: x86/CPU/AMD: Don't force the CPB cap when running under a hypervisor
   5
   6 [ Upstream commit 2ac44ab608705948564791ce1d15d43ba81a1e38 ]
   7
   8 For F17h AMD CPUs, the CPB capability ('Core Performance Boost') is forcibly set,
   9 because some versions of that chip incorrectly report that they do not have it.
  10
  11 However, a hypervisor may filter out the CPB capability, for good
  12 reasons. For example, KVM currently does not emulate setting the CPB
  13 bit in MSR_K7_HWCR, and unchecked MSR access errors will be thrown
  14 when trying to set it as a guest:
  15
  16         unchecked MSR access error: WRMSR to 0xc0010015 (tried to write 0x0000000001000011) at rIP: 0xffffffff890638f4 (native_write_msr+0x4/0x20)
  17
  18         Call Trace:
  19         boost_set_msr+0x50/0x80 [acpi_cpufreq]
  20         cpuhp_invoke_callback+0x86/0x560
  21         sort_range+0x20/0x20
  22         cpuhp_thread_fun+0xb0/0x110
  23         smpboot_thread_fn+0xef/0x160
  24         kthread+0x113/0x130
  25         kthread_create_worker_on_cpu+0x70/0x70
  26         ret_from_fork+0x35/0x40
  27
  28 To avoid this issue, don't forcibly set the CPB capability for a CPU
  29 when running under a hypervisor.
  30
  31 Signed-off-by: Frank van der Linden <fllinden@amazon.com>
  32 Acked-by: Borislav Petkov <bp@suse.de>
  33 Cc: Andy Lutomirski <luto@kernel.org>
  34 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  35 Cc: Peter Zijlstra <peterz@infradead.org>
  36 Cc: Thomas Gleixner <tglx@linutronix.de>
  37 Cc: bp@alien8.de
  38 Cc: jiaxun.yang@flygoat.com
  39 Fixes: 0237199186e7 ("x86/CPU/AMD: Set the CPB bit unconditionally on F17h")
  40 Link: http://lkml.kernel.org/r/20190522221745.GA15789@dev-dsk-fllinden-2c-c1893d73.us-west-2.amazon.com
  41 [ Minor edits to the changelog. ]
  42 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  43 Signed-off-by: Sasha Levin <sashal@kernel.org>
  44 ---
  45  arch/x86/kernel/cpu/amd.c | 7 +++++--
  46  1 file changed, 5 insertions(+), 2 deletions(-)
  47
  48 diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
  49 index 6a25278e0092..da1f5e78363e 100644
  50 --- a/arch/x86/kernel/cpu/amd.c
  51 +++ b/arch/x86/kernel/cpu/amd.c
  52 @@ -819,8 +819,11 @@ static void init_amd_zn(struct cpuinfo_x86 *c)
  53  {
  54         set_cpu_cap(c, X86_FEATURE_ZEN);
  55
  56 -       /* Fix erratum 1076: CPB feature bit not being set in CPUID. */
  57 -       if (!cpu_has(c, X86_FEATURE_CPB))
  58 +       /*
  59 +        * Fix erratum 1076: CPB feature bit not being set in CPUID.
  60 +        * Always set it, except when running under a hypervisor.
  61 +        */
  62 +       if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_CPB))
  63                 set_cpu_cap(c, X86_FEATURE_CPB);
  64  }
  65
  66 --
  67 2.20.1
  68