[PATCH 5/6 v2] kvm: powerpc: booke: Add linux pte lookup like booke3s

[Bhushan Bharat-R65777]

> -----Original Message-----
> From: Benjamin Herrenschmidt [mailto:benh at kernel.crashing.org]
> Sent: Saturday, August 03, 2013 9:54 AM
> To: Bhushan Bharat-R65777
> Cc: Wood Scott-B07421; agraf at suse.de; kvm-ppc at vger.kernel.org;
> kvm at vger.kernel.org; linuxppc-dev at lists.ozlabs.org
> Subject: Re: [PATCH 5/6 v2] kvm: powerpc: booke: Add linux pte lookup like
> booke3s
> 
> On Sat, 2013-08-03 at 02:58 +0000, Bhushan Bharat-R65777 wrote:
> > One of the problem I saw was that if I put this code in
> > asm/pgtable-32.h and asm/pgtable-64.h then pte_persent() and other
> > friend function (on which this code depends) are defined in pgtable.h.
> > And pgtable.h includes asm/pgtable-32.h and asm/pgtable-64.h before it
> > defines pte_present() and friends functions.
> >
> > Ok I move wove this in asm/pgtable*.h, initially I fought with myself
> > to take this code in pgtable* but finally end up doing here (got
> > biased by book3s :)).
> 
> Is there a reason why these routines can not be completely generic in pgtable.h
> ?

How about the generic function:

diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index d257d98..21daf28 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -221,6 +221,27 @@ static inline unsigned long pte_update(struct mm_struct *mm,
        return old;
 }

+static inline unsigned long pte_read(pte_t *p)
+{
+#ifdef PTE_ATOMIC_UPDATES
+       pte_t pte;
+       pte_t tmp;
+       __asm__ __volatile__ (
+       "1:     ldarx   %0,0,%3\n"
+       "       andi.   %1,%0,%4\n"
+       "       bne-    1b\n"
+       "       ori     %1,%0,%4\n"
+       "       stdcx.  %1,0,%3\n"
+       "       bne-    1b"
+       : "=&r" (pte), "=&r" (tmp), "=m" (*p)
+       : "r" (p), "i" (_PAGE_BUSY)
+       : "cc");
+
+       return pte;
+#else  
+       return pte_val(*p);
+#endif
+#endif
+}
 static inline int __ptep_test_and_clear_young(struct mm_struct *mm,
                                              unsigned long addr, pte_t *ptep)
 {
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 690c8c2..dad712c 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -254,6 +254,45 @@ static inline pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
 }
 #endif /* !CONFIG_HUGETLB_PAGE */

+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+                                    int writing, unsigned long *pte_sizep)
+{
+       pte_t *ptep;
+       pte_t pte;
+       unsigned long ps = *pte_sizep;
+       unsigned int shift;
+
+       ptep = find_linux_pte_or_hugepte(pgdir, hva, &shift);
+       if (!ptep)
+               return __pte(0);
+       if (shift)
+               *pte_sizep = 1ul << shift;
+       else
+               *pte_sizep = PAGE_SIZE;
+
+       if (ps > *pte_sizep)
+               return __pte(0);
+
+       if (!pte_present(*ptep))
+               return __pte(0);
+
+#ifdef CONFIG_PPC64
+       /* Lock PTE (set _PAGE_BUSY) and read */
+       pte = pte_read(ptep);
+#else
+       pte = pte_val(*ptep);
+#endif
+       if (pte_present(pte)) {
+               pte = pte_mkyoung(pte);
+               if (writing && pte_write(pte))
+                       pte = pte_mkdirty(pte);
+       }
+
+       *ptep = __pte(pte); /* 64bit: Also unlock pte (clear _PAGE_BUSY) */
+
+       return pte;
+}
+
 #endif /* __ASSEMBLY__ */

 #endif /* __KERNEL__ */