linux-kernel - [PATCH 2/4] perf/x86/ibs: Use CPUID region helper

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Message-Id: <20240403153511.75CB9DA0@davehans-spike.ostc.intel.com>
Date: Wed, 03 Apr 2024 08:35:11 -0700
From: Dave Hansen <dave.hansen@...ux.intel.com>
To: linux-kernel@...r.kernel.org
Cc: jgross@...e.com,tglx@...utronix.de,x86@...nel.org,bp@...en8.de,Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [PATCH 2/4] perf/x86/ibs: Use CPUID region helper


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

IBS details are enumerated in an extended CPUID leaf.  But
the support has an open-coded CPUID region check.  Use the
new helper to trim down the code.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
--

Note: this cleanup could take another form:

        if (boot_cpu_data->extended_cpuid_level >= IBS_CPUID_FEATURES)
                caps = cpuid_eax(IBS_CPUID_FEATURES);

that would be one fewer CPUID invocations, but one more
line of code.
---

 b/arch/x86/events/amd/ibs.c |    9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff -puN arch/x86/events/amd/ibs.c~ibs-region-helpers arch/x86/events/amd/ibs.c
--- a/arch/x86/events/amd/ibs.c~ibs-region-helpers	2024-04-02 15:22:59.262912595 -0700
+++ b/arch/x86/events/amd/ibs.c	2024-04-02 15:22:59.262912595 -0700
@@ -1278,18 +1278,13 @@ static __init int perf_event_ibs_init(vo
 
 static __init u32 __get_ibs_caps(void)
 {
-	u32 caps;
-	unsigned int max_level;
+	u32 caps = 0;
 
 	if (!boot_cpu_has(X86_FEATURE_IBS))
 		return 0;
 
-	/* check IBS cpuid feature flags */
-	max_level = cpuid_eax(0x80000000);
-	if (max_level < IBS_CPUID_FEATURES)
-		return IBS_CAPS_DEFAULT;
+	get_cpuid_region_leaf(IBS_CPUID_FEATURES, CPUID_EAX, &caps);
 
-	caps = cpuid_eax(IBS_CPUID_FEATURES);
 	if (!(caps & IBS_CAPS_AVAIL))
 		/* cpuid flags not valid */
 		return IBS_CAPS_DEFAULT;
_