linux-kernel - [PATCH v3] x86/acrn: Set X86_FEATURE_TSC_KNOWN

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Message-Id: <20221129094025.907760-1-fei1.li@intel.com>
Date:   Tue, 29 Nov 2022 17:40:25 +0800
From:   Fei Li <fei1.li@...el.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     bp@...en8.de, peterz@...radead.org, dave.hansen@...el.com,
        gregkh@...uxfoundation.org, tglx@...utronix.de, mingo@...hat.com,
        dave.hansen@...ux.intel.com, hpa@...or.com, yu1.wang@...el.com,
        conghui.chen@...el.com, fengwei.yin@...el.com, junjie.mao@...el.com
Subject: [PATCH v3] x86/acrn: Set X86_FEATURE_TSC_KNOWN_FREQ

Using hypervisor-provided TSC frequency is common practice for guests.
However, for a Linux guest, it may still to reclibrate the ACRN-specific
TSC frequency if X86_FEATURE_TSC_KNOWN_FREQ flag is not set.

When TSC frequency is known (retrieved from ACRN hypervisor), skip TSC
refined calibration by setting X86_FEATURE_TSC_KNOWN_FREQ.

Also remove `inline` for acrn_get_tsc_khz() since it doesn't make sense.

Signed-off-by: Fei Li <fei1.li@...el.com>
Reviewed-by: Yin, Fengwei <fengwei.yin@...el.com>

---
v3: Update the commit message base on Borislav's comments
v2: Detail the commit message
---
 arch/x86/include/asm/acrn.h | 5 -----
 arch/x86/kernel/cpu/acrn.c  | 6 ++++++
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h
index 1dd14381bcb6..aa12c74ea959 100644
--- a/arch/x86/include/asm/acrn.h
+++ b/arch/x86/include/asm/acrn.h
@@ -30,11 +30,6 @@ static inline u32 acrn_cpuid_base(void)
 	return 0;
 }
 
-static inline unsigned long acrn_get_tsc_khz(void)
-{
-	return cpuid_eax(ACRN_CPUID_TIMING_INFO);
-}
-
 /*
  * Hypercalls for ACRN
  *
diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 485441b7f030..c5ff75b6a949 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c
@@ -24,6 +24,12 @@ static u32 __init acrn_detect(void)
 	return acrn_cpuid_base();
 }
 
+static unsigned long acrn_get_tsc_khz(void)
+{
+	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
+	return cpuid_eax(ACRN_CPUID_TIMING_INFO);
+}
+
 static void __init acrn_init_platform(void)
 {
 	/* Setup the IDT for ACRN hypervisor callback */

base-commit: b7b275e60bcd5f89771e865a8239325f86d9927d
-- 
2.34.1