linux-kernel - [PATCH v4 02/12] x86/mtrr: optimize mtrr_calc

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Message-Id: <20230306163425.8324-3-jgross@suse.com>
Date:   Mon,  6 Mar 2023 17:34:15 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v4 02/12] x86/mtrr: optimize mtrr_calc_physbits()

Optimize mtrr_calc_physbits() for better readability.

Drop a stale comment, as reality has made it obsolete.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
V3:
- new patch, split off from previous patch (Boris Petkov)
---
 arch/x86/kernel/cpu/mtrr/mtrr.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 8310bdb111d0..7596ebeab929 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -619,8 +619,6 @@ static struct syscore_ops mtrr_syscore_ops = {
 
 int __initdata changed_by_mtrr_cleanup;
 
-#define SIZE_OR_MASK_BITS(n)  (~((1ULL << ((n) - PAGE_SHIFT)) - 1))
-
 static unsigned int __init mtrr_calc_physbits(bool generic)
 {
 	unsigned int phys_addr;
@@ -628,15 +626,8 @@ static unsigned int __init mtrr_calc_physbits(bool generic)
 	phys_addr = 32;
 
 	if (generic) {
-		size_or_mask = SIZE_OR_MASK_BITS(36);
-		size_and_mask = 0x00f00000;
 		phys_addr = 36;
 
-		/*
-		 * This is an AMD specific MSR, but we assume(hope?) that
-		 * Intel will implement it too when they extend the address
-		 * bus of the Xeon.
-		 */
 		if (cpuid_eax(0x80000000) >= 0x80000008) {
 			phys_addr = cpuid_eax(0x80000008) & 0xff;
 			/* CPUID workaround for Intel 0F33/0F34 CPU */
@@ -647,23 +638,19 @@ static unsigned int __init mtrr_calc_physbits(bool generic)
 			     boot_cpu_data.x86_stepping == 0x4))
 				phys_addr = 36;
 
-			size_or_mask = SIZE_OR_MASK_BITS(phys_addr);
-			size_and_mask = ~size_or_mask & 0xfffff00000ULL;
 		} else if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR &&
 			   boot_cpu_data.x86 == 6) {
 			/*
 			 * VIA C* family have Intel style MTRRs,
 			 * but don't support PAE
 			 */
-			size_or_mask = SIZE_OR_MASK_BITS(32);
-			size_and_mask = 0;
 			phys_addr = 32;
 		}
-	} else {
-		size_or_mask = SIZE_OR_MASK_BITS(32);
-		size_and_mask = 0;
 	}
 
+	size_or_mask = ~((1ULL << (phys_addr - PAGE_SHIFT)) - 1);
+	size_and_mask = ~size_or_mask & 0xfffff00000ULL;
+
 	return phys_addr;
 }
 
-- 
2.35.3