linux-kernel - Re: [PATCH v6 11/16] x86/mtrr: construct a memory map with cache modes

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Message-ID: <20230509121000.GAZFo4GOV9RnygziXH@fat_crate.local>
Date:   Tue, 9 May 2023 14:10:00 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        mikelley@...rosoft.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v6 11/16] x86/mtrr: construct a memory map with cache
 modes

On Tue, May 09, 2023 at 01:47:47PM +0200, Juergen Gross wrote:
> ... this call not being needed at all. We can reach this point only for
> mtrr_if != &generic_mtrr_ops.

Can't be too cautious with that MTRR maze but yeah, this is the MTRRs
disabled path. Ok, so even simpler then. I've renamed it to
generic_rebuild_map() to go along with the rest of the generic.c APIs.

Thx.

---
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 163dca53796c..3a3b985006e2 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -458,8 +458,11 @@ static void map_add_var(void)
  * removals of registers, which are complicated to handle without rebuild of
  * the map.
  */
-static void rebuild_map(void)
+void generic_rebuild_map(void)
 {
+	if (mtrr_if != &generic_mtrr_ops)
+		return;
+
 	cache_map_n = cache_map_fixed;
 
 	map_add_var();
@@ -1127,10 +1130,6 @@ static void generic_set_mtrr(unsigned int reg, unsigned long base,
 
 	cache_enable();
 	local_irq_restore(flags);
-
-	/* On the first CPU rebuild the cache mode memory map. */
-	if (smp_processor_id() == cpumask_first(cpu_online_mask))
-		rebuild_map();
 }
 
 int generic_validate_add_page(unsigned long base, unsigned long size,
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 5fb61bb97ab1..bcde9a754f62 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -187,6 +187,8 @@ static void set_mtrr(unsigned int reg, unsigned long base, unsigned long size,
 				    };
 
 	stop_machine_cpuslocked(mtrr_rendezvous_handler, &data, cpu_online_mask);
+
+	generic_rebuild_map();
 }
 
 /**
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
index 48ffd89cf3a6..81babff29c59 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.h
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.h
@@ -79,3 +79,4 @@ extern const struct mtrr_ops centaur_mtrr_ops;
 
 extern int changed_by_mtrr_cleanup;
 extern int mtrr_cleanup(void);
+void generic_rebuild_map(void);


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette