linux-kernel - [PATCH 04/10] x86/cpu: Refresh DCA leaf reading code

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Message-Id: <20241213205032.476A30FE@davehans-spike.ostc.intel.com>
Date: Fri, 13 Dec 2024 12:50:32 -0800
From: Dave Hansen <dave.hansen@...ux.intel.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org,tglx@...utronix.de,bp@...en8.de,rafael@...nel.org,lenb@...nel.org,dave.jiang@...el.com,irenic.rajneesh@...il.com,david.e.box@...el.com,Dave Hansen <dave.hansen@...ux.intel.com>,zhao1.liu@...el.com
Subject: [PATCH 04/10] x86/cpu: Refresh DCA leaf reading code


From: Dave Hansen <dave.hansen@...ux.intel.com>

The DCA leaf number is also hard-coded in the CPUID level dependency
table. Move its definition to common code and use it.

While at it, fix up the naming and types in the probe code.  All
CPUID data is provided in 32-bit registers, not 'unsigned long'.
Also stop referring to "level_9".  Move away from test_bit()
because the type is no longer an 'unsigned long'.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@...el.com>
---

 b/arch/x86/include/asm/cpuid.h |    3 ++-
 b/arch/x86/kernel/cpu/common.c |    2 +-
 b/drivers/dma/ioat/dca.c       |    8 +++++---
 3 files changed, 8 insertions(+), 5 deletions(-)

diff -puN arch/x86/include/asm/cpuid.h~dca-leaf-checks-1 arch/x86/include/asm/cpuid.h
--- a/arch/x86/include/asm/cpuid.h~dca-leaf-checks-1	2024-12-13 12:45:34.247113987 -0800
+++ b/arch/x86/include/asm/cpuid.h	2024-12-13 12:45:34.255114326 -0800
@@ -21,7 +21,8 @@ enum cpuid_regs_idx {
 	CPUID_EDX,
 };
 
-#define CPUID_MWAIT_LEAF		5
+#define CPUID_MWAIT_LEAF	0x5
+#define CPUID_DCA_LEAF		0x9
 
 #ifdef CONFIG_X86_32
 bool have_cpuid_p(void);
diff -puN arch/x86/kernel/cpu/common.c~dca-leaf-checks-1 arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~dca-leaf-checks-1	2024-12-13 12:45:34.251114156 -0800
+++ b/arch/x86/kernel/cpu/common.c	2024-12-13 12:45:34.255114326 -0800
@@ -638,7 +638,7 @@ struct cpuid_dependent_feature {
 static const struct cpuid_dependent_feature
 cpuid_dependent_features[] = {
 	{ X86_FEATURE_MWAIT,		CPUID_MWAIT_LEAF },
-	{ X86_FEATURE_DCA,		0x00000009 },
+	{ X86_FEATURE_DCA,		CPUID_DCA_LEAF },
 	{ X86_FEATURE_XSAVE,		0x0000000d },
 	{ 0, 0 }
 };
diff -puN drivers/dma/ioat/dca.c~dca-leaf-checks-1 drivers/dma/ioat/dca.c
--- a/drivers/dma/ioat/dca.c~dca-leaf-checks-1	2024-12-13 12:45:34.251114156 -0800
+++ b/drivers/dma/ioat/dca.c	2024-12-13 12:45:34.255114326 -0800
@@ -10,6 +10,8 @@
 #include <linux/interrupt.h>
 #include <linux/dca.h>
 
+#include <asm/cpuid.h>
+
 /* either a kernel change is needed, or we need something like this in kernel */
 #ifndef CONFIG_SMP
 #include <asm/smp.h>
@@ -58,11 +60,11 @@ static int dca_enabled_in_bios(struct pc
 {
 	/* CPUID level 9 returns DCA configuration */
 	/* Bit 0 indicates DCA enabled by the BIOS */
-	unsigned long cpuid_level_9;
+	u32 eax;
 	int res;
 
-	cpuid_level_9 = cpuid_eax(9);
-	res = test_bit(0, &cpuid_level_9);
+	eax = cpuid_eax(CPUID_DCA_LEAF);
+	res = eax & BIT(0);
 	if (!res)
 		dev_dbg(&pdev->dev, "DCA is disabled in BIOS\n");
 
_