On Wed, Nov 11, 2020 at 11:26 AM Mike Rapoport <rppt@xxxxxxxxxx> wrote:
>
> On Wed, Nov 11, 2020 at 10:33:29AM +0100, Arnd Bergmann wrote:
> > On Tue, Nov 10, 2020 at 5:21 PM Mike Rapoport <rppt@xxxxxxxxxx> wrote:
> > > On Tue, Nov 10, 2020 at 12:21:11PM +0100, Arnd Bergmann wrote:
> > > >
> > > > To be on the safe side, we could provoke a compile-time error
> > > > when CONFIG_PHYS_ADDR_T_64BIT is set on a 32-bit
> > > > architecture, but MAX_POSSIBLE_PHYSMEM_BITS is not set.
> > >
> > > Maybe compile time warning and a runtime error in zs_init() if 32 bit
> > > machine has memory above 4G?
> >
> > If the fix is as easy as adding a single line in a header, I think a
> > compile-time
> > error makes it easier, no need to wait for someone to boot a broken
> > system before fixing it.
>
> Not sure it would be as easy as adding a single line in a header for
> MIPS with it's diversity.
I looked up the architecture, and found:
- The pre-MIPS32r1 cores only support 32-bit addressing
- octeon selects PHYS_ADDR_T_64BIT but no longer
supports 32-bit kernels
- Alchemy and netlogic (XLR, XLP) have 36-bit addressing
- CONFIG_XPA implies 40-bit addressing
We should run it by the MIPS maintainers, but I think this patch
is sufficient:
--- a/arch/mips/include/asm/pgtable-32.h
+++ b/arch/mips/include/asm/pgtable-32.h
@@ -154,6 +154,7 @@ static inline void pmd_clear(pmd_t *pmdp)
#if defined(CONFIG_XPA)
+#define MAX_POSSIBLE_PHYSMEM_BITS 40
#define pte_pfn(x) (((unsigned long)((x).pte_high >>
_PFN_SHIFT)) | (unsigned long)((x).pte_low << _PAGE_PRESENT_SHIFT))
static inline pte_t
pfn_pte(unsigned long pfn, pgprot_t prot)
@@ -169,6 +170,7 @@ pfn_pte(unsigned long pfn, pgprot_t prot)
#elif defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
+#define MAX_POSSIBLE_PHYSMEM_BITS 35
#define pte_pfn(x) ((unsigned long)((x).pte_high >> 6))
static inline pte_t pfn_pte(unsigned long pfn, pgprot_t prot)
@@ -183,6 +185,7 @@ static inline pte_t pfn_pte(unsigned long pfn,
pgprot_t prot)
#else
+#define MAX_POSSIBLE_PHYSMEM_BITS 32
#ifdef CONFIG_CPU_VR41XX
#define pte_pfn(x) ((unsigned long)((x).pte >> (PAGE_SHIFT + 2)))
#define pfn_pte(pfn, prot) __pte(((pfn) << (PAGE_SHIFT + 2)) |
pgprot_val(prot))
Arnd
