linux-kernel - Re: [PATCH v3 13/34] m68k: Implement the new page table range API

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Date:   Sun, 5 Mar 2023 15:28:46 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-m68k@...ts.linux-m68k.org
Subject: Re: [PATCH v3 13/34] m68k: Implement the new page table range API

On Sun, Mar 05, 2023 at 11:16:13AM +0100, Geert Uytterhoeven wrote:
> > +               while (nr--) {
> > +                       __asm__ __volatile__("nop\n\t"
> > +                                            ".chip 68040\n\t"
> > +                                            "cpushp %%bc,(%0)\n\t"
> > +                                            ".chip 68k"
> > +                                            : : "a" (paddr + nr * PAGE_SIZE));
> 
> As gcc (9.5.0) keeps on calculating "paddr + nr * PAGE_SIZE"
> inside the loop (albeit using a shift instead of a multiplication),
> please use "paddr" here, followed by "paddr += PAGE_SIZE;".

Thanks.  So this?

+++ b/arch/m68k/include/asm/cacheflush_mm.h
@@ -235,13 +235,14 @@ static inline void __flush_pages_to_ram(void *vaddr, unsigned int nr)
        } else if (CPU_IS_040_OR_060) {
                unsigned long paddr = __pa(vaddr);
 
-               while (nr--) {
+               do {
                        __asm__ __volatile__("nop\n\t"
                                             ".chip 68040\n\t"
                                             "cpushp %%bc,(%0)\n\t"
                                             ".chip 68k"
-                                            : : "a" (paddr + nr * PAGE_SIZE));
-               }
+                                            : : "a" (paddr));
+                       paddr += PAGE_SIZE;
+               } while (--nr);
        } else {
                unsigned long _tmp;
                __asm__ __volatile__("movec %%cacr,%0\n\t"

Also, I noticed that I broke sun3.  It puts the PFN in bits 0-n instead
of 12-n.  New patch coming soon.