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authorAndy Lutomirski <luto@kernel.org>2016-12-09 21:24:07 +0300
committerThomas Gleixner <tglx@linutronix.de>2016-12-19 13:54:21 +0300
commit484d0e5c7943644cc46e7308a8f9d83be598f2b9 (patch)
treefedce8b05aad45a5dc626458b0e649975c43d759 /arch
parent426d1aff3138cf38da14e912df3c75e312f96e9e (diff)
downloadlinux-484d0e5c7943644cc46e7308a8f9d83be598f2b9.tar.xz
x86/microcode/intel: Replace sync_core() with native_cpuid()
The Intel microcode driver is using sync_core() to mean "do CPUID with EAX=1". I want to rework sync_core(), but first the Intel microcode driver needs to stop depending on its current behavior. Reported-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Signed-off-by: Andy Lutomirski <luto@kernel.org> Acked-by: Borislav Petkov <bp@alien8.de> Cc: Juergen Gross <jgross@suse.com> Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Brian Gerst <brgerst@gmail.com> Cc: Matthew Whitehead <tedheadster@gmail.com> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: xen-devel <Xen-devel@lists.xen.org> Link: http://lkml.kernel.org/r/535a025bb91fed1a019c5412b036337ad239e5bb.1481307769.git.luto@kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/microcode/intel.c26
1 files changed, 23 insertions, 3 deletions
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 54d50c3694d8..b624b54912e1 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -368,6 +368,26 @@ next:
return patch;
}
+static void cpuid_1(void)
+{
+ /*
+ * According to the Intel SDM, Volume 3, 9.11.7:
+ *
+ * CPUID returns a value in a model specific register in
+ * addition to its usual register return values. The
+ * semantics of CPUID cause it to deposit an update ID value
+ * in the 64-bit model-specific register at address 08BH
+ * (IA32_BIOS_SIGN_ID). If no update is present in the
+ * processor, the value in the MSR remains unmodified.
+ *
+ * Use native_cpuid -- this code runs very early and we don't
+ * want to mess with paravirt.
+ */
+ unsigned int eax = 1, ebx, ecx = 0, edx;
+
+ native_cpuid(&eax, &ebx, &ecx, &edx);
+}
+
static int collect_cpu_info_early(struct ucode_cpu_info *uci)
{
unsigned int val[2];
@@ -393,7 +413,7 @@ static int collect_cpu_info_early(struct ucode_cpu_info *uci)
native_wrmsrl(MSR_IA32_UCODE_REV, 0);
/* As documented in the SDM: Do a CPUID 1 here */
- sync_core();
+ cpuid_1();
/* get the current revision from MSR 0x8B */
native_rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
@@ -593,7 +613,7 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
native_wrmsrl(MSR_IA32_UCODE_REV, 0);
/* As documented in the SDM: Do a CPUID 1 here */
- sync_core();
+ cpuid_1();
/* get the current revision from MSR 0x8B */
native_rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
@@ -805,7 +825,7 @@ static int apply_microcode_intel(int cpu)
wrmsrl(MSR_IA32_UCODE_REV, 0);
/* As documented in the SDM: Do a CPUID 1 here */
- sync_core();
+ cpuid_1();
/* get the current revision from MSR 0x8B */
rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);