x86/microcode/amd: Extract current patch level read to a function

Pave the way for checking the current patch level of the
microcode in a core. We want to be able to do stuff depending on
the patch level - in this case decide whether to update or not.
But that will be added in a later patch.

Drop unused local var uci assignment, while at it.

Integrate a fix for 32-bit and CONFIG_PARAVIRT from Takashi Iwai:

 Use native_rdmsr() in check_current_patch_level() because with
 CONFIG_PARAVIRT enabled and on 32-bit, where we run before
 paging has been enabled, we cannot deref pv_info yet. Or we
 could, but we'd need to access its physical address. This way of
 fixing it is simpler. See:

   https://bugzilla.suse.com/show_bug.cgi?id=943179 for the background.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Takashi Iwai <tiwai@suse.com>:
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/1444641762-9437-6-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/microcode_amd.h

@@ -76,4 +76,5 @@ static inline int __init save_microcode_in_initrd_amd(void) { return -EINVAL; }
 void reload_ucode_amd(void) {}
 #endif
 
+extern bool check_current_patch_level(u32 *rev);
 #endif /* _ASM_X86_MICROCODE_AMD_H */

arch/x86/kernel/cpu/microcode/amd.c

@@ -177,6 +177,25 @@ static unsigned int verify_patch_size(u8 family, u32 patch_size,
 	return patch_size;
 }
 
+/*
+ * Check the current patch level on this CPU.
+ *
+ * @rev: Use it to return the patch level. It is set to 0 in the case of
+ * error.
+ *
+ * Returns:
+ *  - true: if update should stop
+ *  - false: otherwise
+ */
+bool check_current_patch_level(u32 *rev)
+{
+	u32 dummy;
+
+	native_rdmsr(MSR_AMD64_PATCH_LEVEL, *rev, dummy);
+
+	return false;
+}
+
 int __apply_microcode_amd(struct microcode_amd *mc_amd)
 {
 	u32 rev, dummy;
@@ -197,7 +216,7 @@ int apply_microcode_amd(int cpu)
 	struct microcode_amd *mc_amd;
 	struct ucode_cpu_info *uci;
 	struct ucode_patch *p;
-	u32 rev, dummy;
+	u32 rev;
 
 	BUG_ON(raw_smp_processor_id() != cpu);
 
@@ -210,7 +229,8 @@ int apply_microcode_amd(int cpu)
 	mc_amd  = p->data;
 	uci->mc = p->data;
 
-	rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
+	if (check_current_patch_level(&rev))
+		return -1;
 
 	/* need to apply patch? */
 	if (rev >= mc_amd->hdr.patch_id) {

arch/x86/kernel/cpu/microcode/amd_early.c

@@ -196,9 +196,8 @@ static void apply_ucode_in_initrd(void *ucode, size_t size, bool save_patch)
 		return;
 	}
 
-	/* find ucode and update if needed */
-
-	native_rdmsr(MSR_AMD64_PATCH_LEVEL, rev, eax);
+	if (check_current_patch_level(&rev))
+		return;
 
 	while (left > 0) {
 		struct microcode_amd *mc;
@@ -319,7 +318,6 @@ static void __init get_bsp_sig(void)
 void load_ucode_amd_ap(void)
 {
 	unsigned int cpu = smp_processor_id();
-	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	struct equiv_cpu_entry *eq;
 	struct microcode_amd *mc;
 	u32 rev, eax;
@@ -332,10 +330,8 @@ void load_ucode_amd_ap(void)
 	if (!container)
 		return;
 
-	rdmsr(MSR_AMD64_PATCH_LEVEL, rev, eax);
-
-	uci->cpu_sig.rev = rev;
-	uci->cpu_sig.sig = eax;
+	if (check_current_patch_level(&rev))
+		return;
 
 	eax = cpuid_eax(0x00000001);
 	eq  = (struct equiv_cpu_entry *)(container + CONTAINER_HDR_SZ);
@@ -424,9 +420,10 @@ int __init save_microcode_in_initrd_amd(void)
 void reload_ucode_amd(void)
 {
 	struct microcode_amd *mc;
-	u32 rev, eax;
+	u32 rev;
 
-	rdmsr(MSR_AMD64_PATCH_LEVEL, rev, eax);
+	if (check_current_patch_level(&rev))
+		return;
 
 	mc = (struct microcode_amd *)amd_ucode_patch;