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From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
To:     x86@kernel.org
Cc:     sherry.hurwitz@amd.com, linux-kernel@vger.kernel.org,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: [PATCH] x86/cpu/AMD: Fix CPB bit for more processors
Date:   Fri, 16 Nov 2018 13:31:06 +0800
Message-Id: <20181116053106.11571-1-jiaxun.yang@flygoat.com>
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Sender: linux-kernel-owner@vger.kernel.org
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CPUID Fn8000_0007_EDX[CPB] is wrongly 0 on Model 17,
Stepping 0, but revision guide has not been released for
newer Family 17h models.

Tesed on AMD "Ryzen 7 2700U with Radeon Vega Mobile Gfx"
and "AMD Ryzen 5 2500U with Radeon Vega Mobile Gfx",
their CPUID Fn0000_0001_EAX is 0x00810f10 and should have
CPB feature according AMD product specifications, however
their Fn8000_0007_EDX is 0x00006599, indicating they don't
support CPB feature.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 arch/x86/kernel/cpu/amd.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index eeea634bee0a..7db43ef8e97e 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -821,8 +821,12 @@ static void init_amd_zn(struct cpuinfo_x86 *c)
 	/*
 	 * Fix erratum 1076: CPB feature bit not being set in CPUID. It affects
 	 * all up to and including B1.
+	 *
+	 * Revision guide for Family 17h, Model 17 has not been released, but
+	 * Model 17, Stepping 0 have the same issue.
 	 */
-	if (c->x86_model <= 1 && c->x86_stepping <= 1)
+	if ((c->x86_model <= 1 && c->x86_stepping <= 1) ||	\
+		(c->x86_model == 17 && c->x86_stepping == 0))
 		set_cpu_cap(c, X86_FEATURE_CPB);
 }
 
-- 
2.19.1