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

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Hi Matthew, Geert,

sorry, I missed that one when it got posted ...

On 6/03/23 04:28, Matthew Wilcox wrote:
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;".

Are we certain that contiguous vaddr always maps to contiguous paddr?

If not, I'd suggest we increment vaddr inside the loop, and use __pa() each time:

+++ 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) {
- 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" __pa(vaddr));
+                       vaddr += PAGE_SIZE;
+               } while (--nr);
         } else {
                 unsigned long _tmp;
                 __asm__ __volatile__("movec %%cacr,%0\n\t"

(just edited Matthew's patch in the mail editor, untested, may not apply cleanly ...)

Cheers,

    Michael





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