On Thu, May 17, 2018 at 11:35:47AM +0100, Marc Zyngier wrote: > There is no need to perform cache maintenance operations when > creating the HYP page tables if we have the multiprocessing > extensions. ARMv7 mandates them with the virtualization support, > and ARMv8 just mandates them unconditionally. > > Let's remove these operations. > > Signed-off-by: Marc Zyngier <marc.zyng...@arm.com> > --- > virt/kvm/arm/mmu.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c > index ba66bf7ae299..acbfea09578c 100644 > --- a/virt/kvm/arm/mmu.c > +++ b/virt/kvm/arm/mmu.c > @@ -578,7 +578,6 @@ 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); > } > @@ -605,7 +604,6 @@ 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); > @@ -638,7 +636,6 @@ static int create_hyp_pud_mappings(pgd_t *pgd, unsigned > long start, > } > pud_populate(NULL, pud, pmd); > get_page(virt_to_page(pud)); > - kvm_flush_dcache_to_poc(pud, sizeof(*pud)); > } > > next = pud_addr_end(addr, end); > @@ -675,7 +672,6 @@ static int __create_hyp_mappings(pgd_t *pgdp, unsigned > long ptrs_per_pgd, > } > pgd_populate(NULL, pgd, pud); > get_page(virt_to_page(pgd)); > - kvm_flush_dcache_to_poc(pgd, sizeof(*pgd)); > } > > next = pgd_addr_end(addr, end); > @@ -685,6 +681,7 @@ static int __create_hyp_mappings(pgd_t *pgdp, unsigned > long ptrs_per_pgd, > pfn += (next - addr) >> PAGE_SHIFT; > } while (addr = next, addr != end); > out: > + dsb(ishst);
I think you need a dsb(ishst) wherever you had a kvm_flush_dcache_to_poc() previously. Otherwise, the page table walker could see stale values. e.g. after you update a bunch of PTE entries and point a PMD entry at those, the PTW could see the updated PMD entry, but see stale PTE entries, which could be garbage. That said, I think for ensuring the *order* those become visible in, you only need a dmb(ishst), and the ensure they *are visible* you need a DSB(ISHST) at the end. Thanks, Mark. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
