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Subject[PATCH] x86/microcode: Do the family check first
Date
From: Borislav Petkov <bp@suse.de>

On CPUs like AMD's Geode, for example, we shouldn't even try to load
microcode because they do not support the modern microcode loading
interface.

However, we do the family check *after* the other checks whether the
loader has been disabled on the command line or whether we're running in
a guest.

So move the family checks first in order to exit early if we're being
loaded on an unsupported family.

Reported-and-tested-by: Sven Glodowski <glodi1@arcor.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org> # 4.11..
Link: http://bugzilla.suse.com/show_bug.cgi?id=1061396
---
arch/x86/kernel/cpu/microcode/core.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 86e8f0b2537b..c4fa4a85d4cb 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -122,9 +122,6 @@ static bool __init check_loader_disabled_bsp(void)
bool *res = &dis_ucode_ldr;
#endif

- if (!have_cpuid_p())
- return *res;
-
/*
* CPUID(1).ECX[31]: reserved for hypervisor use. This is still not
* completely accurate as xen pv guests don't see that CPUID bit set but
@@ -166,24 +163,36 @@ bool get_builtin_firmware(struct cpio_data *cd, const char *name)
void __init load_ucode_bsp(void)
{
unsigned int cpuid_1_eax;
+ bool intel = true;

- if (check_loader_disabled_bsp())
+ if (!have_cpuid_p())
return;

cpuid_1_eax = native_cpuid_eax(1);

switch (x86_cpuid_vendor()) {
case X86_VENDOR_INTEL:
- if (x86_family(cpuid_1_eax) >= 6)
- load_ucode_intel_bsp();
+ if (x86_family(cpuid_1_eax) < 6)
+ return;
break;
+
case X86_VENDOR_AMD:
- if (x86_family(cpuid_1_eax) >= 0x10)
- load_ucode_amd_bsp(cpuid_1_eax);
+ if (x86_family(cpuid_1_eax) < 0x10)
+ return;
+ intel = false;
break;
+
default:
- break;
+ return;
}
+
+ if (check_loader_disabled_bsp())
+ return;
+
+ if (intel)
+ load_ucode_intel_bsp();
+ else
+ load_ucode_amd_bsp(cpuid_1_eax);
}

static bool check_loader_disabled_ap(void)
--
2.13.0
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