linux-kernel - [PATCH v11 1/12] x86, mm, pat: Cleanup init flags in pat

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Message-Id: <1432940350-1802-2-git-send-email-toshi.kani@hp.com>
Date:	Fri, 29 May 2015 16:58:59 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	bp@...en8.de, hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, arnd@...db.de
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-nvdimm@...ts.01.org, jgross@...e.com,
	stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br,
	yigal@...xistor.com, konrad.wilk@...cle.com, Elliott@...com,
	mcgrof@...e.com, hch@....de, Toshi Kani <toshi.kani@...com>
Subject: [PATCH v11 1/12] x86, mm, pat: Cleanup init flags in pat_init()

From: Toshi Kani <toshi.kani@...com>

pat_init() uses two flags, 'boot_cpu' and 'boot_pat_state', for
tracking the boot CPU's initialization status.  'boot_pat_state'
is also overloaded to carry the boot PAT value.

This patch cleans this up by replacing them with a new single
flag, 'boot_cpu_done', to track the boot CPU's initialization
status.  'boot_pat_state' is only used to carry the boot PAT
value as a result.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Toshi Kani <toshi.kani@...com>
---
 arch/x86/mm/pat.c |   40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index a1c9654..e1ec6a7 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -197,24 +197,29 @@ void pat_init_cache_modes(void)
 void pat_init(void)
 {
 	u64 pat;
-	bool boot_cpu = !boot_pat_state;
+	static bool boot_cpu_done;
 
 	if (!pat_enabled())
 		return;
 
-	if (!cpu_has_pat) {
-		if (!boot_pat_state) {
+	if (!boot_cpu_done) {
+		if (!cpu_has_pat) {
 			pat_disable("PAT not supported by CPU.");
 			return;
-		} else {
-			/*
-			 * If this happens we are on a secondary CPU, but
-			 * switched to PAT on the boot CPU. We have no way to
-			 * undo PAT.
-			 */
-			pr_err("x86/PAT: PAT enabled, but not supported by secondary CPU\n");
-			BUG();
 		}
+
+		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
+		if (!boot_pat_state) {
+			pat_disable("PAT read returns always zero, disabled.");
+			return;
+		}
+	} else if (!cpu_has_pat) {
+		/*
+		 * If this happens we are on a secondary CPU, but
+		 * switched to PAT on the boot CPU. We have no way to
+		 * undo PAT.
+		 */
+		panic("PAT enabled, but not supported by secondary CPU\n");
 	}
 
 	/* Set PWT to Write-Combining. All other bits stay the same */
@@ -233,19 +238,12 @@ void pat_init(void)
 	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
 	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
 
-	/* Boot CPU check */
-	if (!boot_pat_state) {
-		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-		if (!boot_pat_state) {
-			pat_disable("PAT read returns always zero, disabled.");
-			return;
-		}
-	}
-
 	wrmsrl(MSR_IA32_CR_PAT, pat);
 
-	if (boot_cpu)
+	if (!boot_cpu_done) {
 		pat_init_cache_modes();
+		boot_cpu_done = true;
+	}
 }
 
 #undef PAT
--
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