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

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Date:   Tue, 9 May 2023 13:36:40 +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 02, 2023 at 02:09:26PM +0200, Juergen Gross wrote:
> @@ -841,6 +1137,10 @@ 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();

I still don't like this. Anything against doing this instead?

---
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 163dca53796c..e69c8c56897f 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 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/legacy.c b/arch/x86/kernel/cpu/mtrr/legacy.c
index d25882fcf181..30a3d51d06e0 100644
--- a/arch/x86/kernel/cpu/mtrr/legacy.c
+++ b/arch/x86/kernel/cpu/mtrr/legacy.c
@@ -67,6 +67,7 @@ static void mtrr_restore(void)
 				     mtrr_value[i].ltype);
 		}
 	}
+	rebuild_map();
 }
 
 static struct syscore_ops mtrr_syscore_ops = {
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 5fb61bb97ab1..10608c7f9606 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);
+
+	rebuild_map();
 }
 
 /**
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
index 48ffd89cf3a6..286ce89ce7f1 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 rebuild_map(void);

-- 
Regards/Gruss,
    Boris.

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