On Tue, May 14, 2013 at 12:11:36PM +0100, Marc Zyngier wrote:
> Patch 5a677ce044f1 (ARM: KVM: switch to a dual-step HYP init code)
> introduced code that flushes page tables to the point of coherency.
> This is overkill (point of unification is enough and already done),
> and actually not required if running on a SMP capable platform
> (the HW PTW can snoop other cpus' L1).
>
> Remove this code and let ae8a8b9553bd (ARM: 7691/1: mm: kill unused
> TLB_CAN_READ_FROM_L1_CACHE and use ALT_SMP instead) turn it into
> a no-op for SMP ARMv7.
>
> Reported-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_mmu.h | 17 +++++++++++------
> arch/arm/kvm/mmu.c | 7 ++++---
> 2 files changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index 472ac70..8c03c96 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -65,11 +65,6 @@ void kvm_clear_hyp_idmap(void);
> static inline void kvm_set_pte(pte_t *pte, pte_t new_pte)
> {
> pte_val(*pte) = new_pte;
> - /*
> - * flush_pmd_entry just takes a void pointer and cleans the necessary
> - * cache entries, so we can reuse the function for ptes.
> - */
> - flush_pmd_entry(pte);
> }
>
> static inline bool kvm_is_write_fault(unsigned long hsr)
> @@ -83,9 +78,19 @@ static inline bool kvm_is_write_fault(unsigned long hsr)
> return true;
> }
>
> +static inline void kvm_clean_dcache_area(void *addr, size_t size)
> +{
> + clean_dcache_area(addr, size);
> +}
> +
> +static inline void kvm_clean_pte_entry(pte_t *pte)
> +{
> + kvm_clean_dcache_area(pte, sizeof(*pte));
> +}
> +
> static inline void kvm_clean_pgd(pgd_t *pgd)
> {
> - clean_dcache_area(pgd, PTRS_PER_S2_PGD * sizeof(pgd_t));
> + kvm_clean_dcache_area(pgd, PTRS_PER_S2_PGD * sizeof(pgd_t));
> }
>
> static inline void kvm_clean_pmd_entry(pmd_t *pmd)
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 84ba67b..451bad3 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -113,6 +113,7 @@ static void clear_pte_entry(struct kvm *kvm, pte_t *pte, phys_addr_t addr)
> {
> if (pte_present(*pte)) {
> kvm_set_pte(pte, __pte(0));
> + kvm_clean_pte_entry(pte);
> put_page(virt_to_page(pte));
> kvm_tlb_flush_vmid_ipa(kvm, addr);
> }
> @@ -234,9 +235,10 @@ static void create_hyp_pte_mappings(pmd_t *pmd, unsigned long start,
> pte = pte_offset_kernel(pmd, addr);
> kvm_set_pte(pte, pfn_pte(pfn, prot));
> get_page(virt_to_page(pte));
> - kvm_flush_dcache_to_poc(pte, sizeof(*pte));
> pfn++;
> } while (addr += PAGE_SIZE, addr != end);
> +
> + kvm_clean_dcache_area((void *)start, end - start);
> }
>
> static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
> @@ -261,7 +263,6 @@ static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
> }
> pmd_populate_kernel(NULL, pmd, pte);
> get_page(virt_to_page(pmd));
> - kvm_flush_dcache_to_poc(pmd, sizeof(*pmd));
> }
>
> next = pmd_addr_end(addr, end);
> @@ -299,7 +300,6 @@ static int __create_hyp_mappings(pgd_t *pgdp,
> }
> pud_populate(NULL, pud, pmd);
> get_page(virt_to_page(pud));
> - kvm_flush_dcache_to_poc(pud, sizeof(*pud));
> }
>
> next = pgd_addr_end(addr, end);
> @@ -469,6 +469,7 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
> /* Create 2nd stage page table mapping - Level 3 */
> old_pte = *pte;
> kvm_set_pte(pte, *new_pte);
> + kvm_clean_pte_entry(pte);
> if (pte_present(old_pte))
> kvm_tlb_flush_vmid_ipa(kvm, addr);
> else
> --
> 1.8.2.3
>
>
I don't care for this change, you have three places where you call
kvm_set_pte and immediately follow with kvm_clean_pte_entry now, just to
optimize the uncommon case only relevant when creating new VMs, and at
the same time do things differently from the rest of the kernel with
set_pte functions (yes, I know it's a static in this file, but that
doesn't mean that readers of this file wouldn't make that association).
The next function that calls kvm_set_pte must now also remember to call
the clean functions, bah.
I think the kvm_clean_pte_entry should just be called from within
kvm_set_pte.
-Christoffer
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