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   1 From foo@baz Fri Feb 23 17:12:49 CET 2018
   2 From: Arnd Bergmann <arnd@arndb.de>
   3 Date: Tue, 20 Feb 2018 12:55:05 +0100
   4 Subject: x86/microcode/AMD: Change load_microcode_amd()'s param to bool to fix preemptibility bug
   5 To: stable@vger.kernel.org
   6 Cc: Greg KH <gregkh@linuxfoundation.org>, linux-kernel@vger.kernel.org, Borislav Petkov <bp@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>, Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org, Borislav Petkov <bp@alien8.de>, Tom Lendacky <thomas.lendacky@amd.com>
   7 Message-ID: <20180220115527.1806578-19-arnd@arndb.de>
   8
   9 From: Borislav Petkov <bp@suse.de>
  10
  11 commit dac6ca243c4c49a9ca7507d3d66140ebfac8b04b upstream.
  12
  13 With CONFIG_DEBUG_PREEMPT enabled, I get:
  14
  15   BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
  16   caller is debug_smp_processor_id
  17   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.12.0-rc2+ #2
  18   Call Trace:
  19    dump_stack
  20    check_preemption_disabled
  21    debug_smp_processor_id
  22    save_microcode_in_initrd_amd
  23    ? microcode_init
  24    save_microcode_in_initrd
  25    ...
  26
  27 because, well, it says it above, we're using smp_processor_id() in
  28 preemptible code.
  29
  30 But passing the CPU number is not really needed. It is only used to
  31 determine whether we're on the BSP, and, if so, to save the microcode
  32 patch for early loading.
  33
  34  [ We don't absolutely need to do it on the BSP but we do that
  35    customarily there. ]
  36
  37 Instead, convert that function parameter to a boolean which denotes
  38 whether the patch should be saved or not, thereby avoiding the use of
  39 smp_processor_id() in preemptible code.
  40
  41 Signed-off-by: Borislav Petkov <bp@suse.de>
  42 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  43 Cc: Peter Zijlstra <peterz@infradead.org>
  44 Cc: Thomas Gleixner <tglx@linutronix.de>
  45 Link: http://lkml.kernel.org/r/20170528200414.31305-1-bp@alien8.de
  46 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  47 [arnd: rebased to 4.9, after running into warning:
  48  arch/x86/kernel/cpu/microcode/amd.c:881:30: self-comparison always evaluates to true]
  49 Signed-off-by: Arnd Bergmann <arnd@arndb.de>
  50 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  51 ---
  52  arch/x86/include/asm/microcode_amd.h |    1 -
  53  arch/x86/kernel/cpu/microcode/amd.c  |   17 +++++++++++------
  54  2 files changed, 11 insertions(+), 7 deletions(-)
  55
  56 --- a/arch/x86/include/asm/microcode_amd.h
  57 +++ b/arch/x86/include/asm/microcode_amd.h
  58 @@ -59,7 +59,6 @@ static inline u16 find_equiv_id(struct e
  59
  60  extern int __apply_microcode_amd(struct microcode_amd *mc_amd);
  61  extern int apply_microcode_amd(int cpu);
  62 -extern enum ucode_state load_microcode_amd(int cpu, u8 family, const u8 *data, size_t size);
  63
  64  #define PATCH_MAX_SIZE PAGE_SIZE
  65  extern u8 amd_ucode_patch[PATCH_MAX_SIZE];
  66 --- a/arch/x86/kernel/cpu/microcode/amd.c
  67 +++ b/arch/x86/kernel/cpu/microcode/amd.c
  68 @@ -131,6 +131,9 @@ static size_t compute_container_size(u8
  69         return size;
  70  }
  71
  72 +static enum ucode_state
  73 +load_microcode_amd(bool save, u8 family, const u8 *data, size_t size);
  74 +
  75  /*
  76   * Early load occurs before we can vmalloc(). So we look for the microcode
  77   * patch container file in initrd, traverse equivalent cpu table, look for a
  78 @@ -438,7 +441,7 @@ int __init save_microcode_in_initrd_amd(
  79         eax   = cpuid_eax(0x00000001);
  80         eax   = ((eax >> 8) & 0xf) + ((eax >> 20) & 0xff);
  81
  82 -       ret = load_microcode_amd(smp_processor_id(), eax, container, container_size);
  83 +       ret = load_microcode_amd(true, eax, container, container_size);
  84         if (ret != UCODE_OK)
  85                 retval = -EINVAL;
  86
  87 @@ -854,7 +857,8 @@ static enum ucode_state __load_microcode
  88         return UCODE_OK;
  89  }
  90
  91 -enum ucode_state load_microcode_amd(int cpu, u8 family, const u8 *data, size_t size)
  92 +static enum ucode_state
  93 +load_microcode_amd(bool save, u8 family, const u8 *data, size_t size)
  94  {
  95         enum ucode_state ret;
  96
  97 @@ -868,8 +872,8 @@ enum ucode_state load_microcode_amd(int
  98
  99  #ifdef CONFIG_X86_32
 100         /* save BSP's matching patch for early load */
 101 -       if (cpu_data(cpu).cpu_index == boot_cpu_data.cpu_index) {
 102 -               struct ucode_patch *p = find_patch(cpu);
 103 +       if (save) {
 104 +               struct ucode_patch *p = find_patch(0);
 105                 if (p) {
 106                         memset(amd_ucode_patch, 0, PATCH_MAX_SIZE);
 107                         memcpy(amd_ucode_patch, p->data, min_t(u32, ksize(p->data),
 108 @@ -901,11 +905,12 @@ static enum ucode_state request_microcod
 109  {
 110         char fw_name[36] = "amd-ucode/microcode_amd.bin";
 111         struct cpuinfo_x86 *c = &cpu_data(cpu);
 112 +       bool bsp = c->cpu_index == boot_cpu_data.cpu_index;
 113         enum ucode_state ret = UCODE_NFOUND;
 114         const struct firmware *fw;
 115
 116         /* reload ucode container only on the boot cpu */
 117 -       if (!refresh_fw || c->cpu_index != boot_cpu_data.cpu_index)
 118 +       if (!refresh_fw || !bsp)
 119                 return UCODE_OK;
 120
 121         if (c->x86 >= 0x15)
 122 @@ -922,7 +927,7 @@ static enum ucode_state request_microcod
 123                 goto fw_release;
 124         }
 125
 126 -       ret = load_microcode_amd(cpu, c->x86, fw->data, fw->size);
 127 +       ret = load_microcode_amd(bsp, c->x86, fw->data, fw->size);
 128
 129   fw_release:
 130         release_firmware(fw);