linux-kernel - Re: [PATCH] highmem: fix highmem for xtensa

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Date:   Fri, 13 Nov 2020 14:40:43 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Max Filippov <jcmvbkbc@...il.com>, linux-xtensa@...ux-xtensa.org
Cc:     Chris Zankel <chris@...kel.net>, linux-kernel@...r.kernel.org,
        Max Filippov <jcmvbkbc@...il.com>
Subject: Re: [PATCH] highmem: fix highmem for xtensa

Max,

On Fri, Nov 13 2020 at 04:23, Max Filippov wrote:
> Fixmap on xtensa grows upwards, i.e. bigger fixmap entry index
> corresponds to a higher virtual address. This was lost in highmem
> generalization resulting in the following runtime warnings:

Sorry for not noticing.

> Fix it by adding __ARCH_HAS_POSITIVE_FIXMAP macro and implementing
> vaddr_in_fixmap and fixmap_pte primitives differently depending on
> whether it is defined or not.

What's wrong with just doing the obvious and making the fixmap defines
the other way round?

Thanks,

        tglx
---

diff --git a/arch/xtensa/include/asm/fixmap.h b/arch/xtensa/include/asm/fixmap.h
index 92049b61c351..ee17e46f3b44 100644
--- a/arch/xtensa/include/asm/fixmap.h
+++ b/arch/xtensa/include/asm/fixmap.h
@@ -37,8 +37,8 @@
 enum fixed_addresses {
 #ifdef CONFIG_HIGHMEM
 	/* reserved pte's for temporary kernel mappings */
-	FIX_KMAP_BEGIN,
-	FIX_KMAP_END = FIX_KMAP_BEGIN +
+	FIX_KMAP_END,
+	FIX_KMAP_BEGIN = FIX_KMAP_END +
 		(KM_MAX_IDX * NR_CPUS * DCACHE_N_COLORS) - 1,
 #endif
 	__end_of_fixed_addresses