Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> wrote:
> From: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com>
>
> We can find pte that are splitting while walking page tables. Return
> None pte in that case.
Can you expand on this more please. There are a lot of details below
like removing a ldarx/stdcx loop that should be better described here.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/kvm_book3s_64.h | 51
> ++++++++++++++++++--------------
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 7 +++--
> arch/powerpc/kvm/book3s_hv_rm_mmu.c | 4 +--
> 3 files changed, 34 insertions(+), 28 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h
> b/arch/powerpc/include/asm/kvm_book3s_64.h
> index 9c1ff33..ce20f7e 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_64.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_64.h
> @@ -162,33 +162,40 @@ static inline int hpte_cache_flags_ok(unsigned long
> ptel, unsigned long io_type)
> * Lock and read a linux PTE. If it's present and writable, atomically
> * set dirty and referenced bits and return the PTE, otherwise return 0.
This is comment still valid now the ldarx/stdcx is gone?
> */
> -static inline pte_t kvmppc_read_update_linux_pte(pte_t *p, int writing)
> +static inline pte_t kvmppc_read_update_linux_pte(pte_t *ptep, int writing,
> + unsigned int hugepage)
> {
> - pte_t pte, tmp;
> -
> - /* wait until _PAGE_BUSY is clear then set it atomically */
> - __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");
> -
> - if (pte_present(pte)) {
> - pte = pte_mkyoung(pte);
> - if (writing && pte_write(pte))
> - pte = pte_mkdirty(pte);
> - }
> + pte_t old_pte, new_pte = __pte(0);
> +repeat:
> + do {
> + old_pte = pte_val(*ptep);
> + /*
> + * wait until _PAGE_BUSY is clear then set it atomically
> + */
> + if (unlikely(old_pte & _PAGE_BUSY))
> + goto repeat;
continue here? Please don't create looping primitives.
> +
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + /* If hugepage and is trans splitting return None */
> + if (unlikely(hugepage &&
> + pmd_trans_splitting(pte_pmd(old_pte))))
Comment looks much like the code... seems redundant.
> + return __pte(0);
> +#endif
>
> - *p = pte; /* clears _PAGE_BUSY */
> + /* If pte is not present return None */
> + if (unlikely(!(old_pte & _PAGE_PRESENT)))
> + return __pte(0);
>
> - return pte;
> + new_pte = pte_mkyoung(old_pte);
> + if (writing && pte_write(old_pte))
> + new_pte = pte_mkdirty(new_pte);
> +
> + } while (old_pte != __cmpxchg_u64((unsigned long *)ptep,
> + old_pte, new_pte));
> + return new_pte;
> }
>
> +
Whitespace
> /* Return HPTE cache control bits corresponding to Linux pte bits */
> static inline unsigned long hpte_cache_bits(unsigned long pte_val)
> {
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 5880dfb..e1a9415 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -675,6 +675,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run,
> struct kvm_vcpu *vcpu,
> }
> /* if the guest wants write access, see if that is OK */
> if (!writing && hpte_is_writable(r)) {
> + unsigned int shift;
> pte_t *ptep, pte;
>
> /*
> @@ -683,9 +684,9 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run,
> struct kvm_vcpu *vcpu,
> */
> rcu_read_lock_sched();
> ptep = find_linux_pte_or_hugepte(current->mm->pgd,
> - hva, NULL);
> - if (ptep && pte_present(*ptep)) {
> - pte = kvmppc_read_update_linux_pte(ptep, 1);
> + hva, &shift);
> + if (ptep) {
> + pte = kvmppc_read_update_linux_pte(ptep, 1,
> shift);
> if (pte_write(pte))
> write_ok = 1;
> }
> diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> index dcf892d..39ae723 100644
> --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> @@ -150,9 +150,7 @@ static pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long
> hva,
> *pte_sizep = PAGE_SIZE;
> if (ps > *pte_sizep)
> return __pte(0);
> - if (!pte_present(*ptep))
> - return __pte(0);
> - return kvmppc_read_update_linux_pte(ptep, writing);
> + return kvmppc_read_update_linux_pte(ptep, writing, shift);
'shift' goes into the new 'hugepage' parameter? Doesn't seem logical?
Can we harmonise the name to make it less confusing?
Mikey
> }
>
> static inline void unlock_hpte(unsigned long *hpte, unsigned long hpte_v)
> --
> 1.8.1.2
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
