linux-kernel - [PATCH 4/4] x86/microcode/AMD: Use native_cpuid() in load_ucode_amd

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Message-Id: <20161218164414.9649-5-bp@alien8.de>
Date:   Sun, 18 Dec 2016 17:44:14 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Jürgen Gross <jgross@...e.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/4] x86/microcode/AMD: Use native_cpuid() in load_ucode_amd_bsp()

From: Boris Ostrovsky <boris.ostrovsky@...cle.com>

When CONFIG_PARAVIRT is selected, cpuid() becomes a call. Since
for 32-bit kernels load_ucode_amd_bsp() is executed before paging
is enabled the call cannot be completed (as kernel virtual addresses
are not reachable yet).

Use native_cpuid() instead which is an asm wrapper for the CPUID
instruction.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Jürgen Gross <jgross@...e.com>
Cc: x86-ml <x86@...nel.org>
Link: http://lkml.kernel.org/r/1481906392-3847-1-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/cpu/microcode/amd.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index dc80acfa922d..6a31e2691f3a 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -301,6 +301,7 @@ static bool get_builtin_microcode(struct cpio_data *cp, unsigned int family)
 void __init load_ucode_amd_bsp(unsigned int family)
 {
 	struct ucode_cpu_info *uci;
+	u32 eax, ebx, ecx, edx;
 	struct cpio_data cp;
 	const char *path;
 	bool use_pa;
@@ -322,7 +323,10 @@ void __init load_ucode_amd_bsp(unsigned int family)
 		return;
 
 	/* Get BSP's CPUID.EAX(1), needed in load_microcode_amd() */
-	uci->cpu_sig.sig = cpuid_eax(1);
+	eax = 1;
+	ecx = 0;
+	native_cpuid(&eax, &ebx, &ecx, &edx);
+	uci->cpu_sig.sig = eax;
 
 	apply_microcode_early_amd(cp.data, cp.size, true, NULL);
 }
-- 
2.11.0