Le 18/06/2020 à 02:58, Michael Ellerman a écrit :
Peter Zijlstra <pet...@infradead.org> writes:
On Thu, Jun 18, 2020 at 12:21:22AM +1000, Michael Ellerman wrote:
Peter Zijlstra <pet...@infradead.org> writes:
On Mon, Jun 15, 2020 at 12:57:59PM +0000, Christophe Leroy wrote:
+#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES)
+#define __HAVE_ARCH_PTEP_GET
+static inline pte_t ptep_get(pte_t *ptep)
+{
+ pte_t pte = {READ_ONCE(ptep->pte), 0, 0, 0};
+
+ return pte;
+}
+#endif
Would it make sense to have a comment with this magic? The casual reader
might wonder WTH just happened when he stumbles on this :-)
I tried writing a helpful comment but it's too late for my brain to form
sensible sentences.
Christophe can you send a follow-up with a comment explaining it? In
particular the zero entries stand out, it's kind of subtle that those
entries are only populated with the right value when we write to the
page table.
static inline pte_t ptep_get(pte_t *ptep)
{
unsigned long val = READ_ONCE(ptep->pte);
/* 16K pages have 4 identical value 4K entries */
pte_t pte = {val, val, val, val);
return pte;
}
Maybe something like that?
I think val wants to be pte_basic_t, but otherwise yeah I like that much
better.
I sent a patch for that.
I'll also send one to fix mm/debug_vm_pgtable.c which also uses
READ_ONCE() to access page table entries.
Christophe