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From: Evalds Iodzevics <evalds.iodzevics@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: gregkh@linuxfoundation.org, tglx@linutronix.de,
	ben@decadent.org.uk, bp@suse.de,
	Evalds Iodzevics <evalds.iodzevics@gmail.com>,
	stable@vger.kernel.org
Subject: [PATCH v2] x86/microcode/intel: replace sync_core() with native_cpuid_reg(eax)
Date: Wed, 22 Apr 2020 11:17:59 +0300	[thread overview]
Message-ID: <20200422081759.1632-1-evalds.iodzevics@gmail.com> (raw)

On Intel it is required to do CPUID(1) before reading the microcode
revision MSR. Current code in 4.4 an 4.9 relies on sync_core() to call
CPUID, unfortunately on 32 bit machines code inside sync_core() always
jumps past CPUID instruction as it depends on data structure boot_cpu_data
witch are not populated correctly so early in boot sequence.

It depends on:
commit 5dedade6dfa2 ("x86/CPU: Add native CPUID variants returning a single
datum")

This patch is for 4.4 but also should apply to 4.9

Signed-off-by: Evalds Iodzevics <evalds.iodzevics@gmail.com>
Cc: stable@vger.kernel.org
---
 arch/x86/include/asm/microcode_intel.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/microcode_intel.h b/arch/x86/include/asm/microcode_intel.h
index 90343ba50485..92ce9c8a508b 100644
--- a/arch/x86/include/asm/microcode_intel.h
+++ b/arch/x86/include/asm/microcode_intel.h
@@ -60,7 +60,7 @@ static inline u32 intel_get_microcode_revision(void)
 	native_wrmsrl(MSR_IA32_UCODE_REV, 0);
 
 	/* As documented in the SDM: Do a CPUID 1 here */
-	sync_core();
+	native_cpuid_eax(1);
 
 	/* get the current revision from MSR 0x8B */
 	native_rdmsr(MSR_IA32_UCODE_REV, dummy, rev);
-- 
2.17.4


             reply	other threads:[~2020-04-22  8:18 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-22  8:17 Evalds Iodzevics [this message]
2020-04-22  8:27 ` [PATCH v2] x86/microcode/intel: replace sync_core() with native_cpuid_reg(eax) Greg KH
  -- strict thread matches above, loose matches on Subject: below --
2020-04-20 12:00 [PATCH] " Evalds Iodzevics
2020-04-21  8:53 ` [PATCH v2] " Evalds Iodzevics
2020-04-21  5:59   ` Greg KH
2020-04-21  6:41     ` Evalds Iodzevics
2020-04-21  7:19       ` Greg KH

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