On Wed, Dec 12, 2018 at 03:17:17PM +1100, Paul Mackerras wrote:
> This adds code to flush the partition-scoped page tables for a radix
> guest when dirty tracking is turned on or off for a memslot. Only the
> guest real addresses covered by the memslot are flushed. The reason
> for this is to get rid of any 2M PTEs in the partition-scoped page
> tables that correspond to host transparent huge pages, so that page
> dirtiness is tracked at a system page (4k or 64k) granularity rather
> than a 2M granularity. The page tables are also flushed when turning
> dirty tracking off so that the memslot's address space can be
> repopulated with THPs if possible.
>
> To do this, we add a new function kvmppc_radix_flush_memslot(). Since
> this does what's needed for kvmppc_core_flush_memslot_hv() on a radix
> guest, we now make kvmppc_core_flush_memslot_hv() call the new
> kvmppc_radix_flush_memslot() rather than calling kvm_unmap_radix()
> for each page in the memslot. This has the effect of fixing a bug in
> that kvmppc_core_flush_memslot_hv() was previously calling
> kvm_unmap_radix() without holding the kvm->mmu_lock spinlock, which
> is required to be held.
>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
> arch/powerpc/include/asm/kvm_book3s.h | 2 ++
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 9 +++++----
> arch/powerpc/kvm/book3s_64_mmu_radix.c | 20 ++++++++++++++++++++
> arch/powerpc/kvm/book3s_hv.c | 17 +++++++++++++++++
> 4 files changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
> index 728d2b7..f8a5ac8 100644
> --- a/arch/powerpc/include/asm/kvm_book3s.h
> +++ b/arch/powerpc/include/asm/kvm_book3s.h
> @@ -222,6 +222,8 @@ extern int kvm_test_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
> unsigned long gfn);
> extern long kvmppc_hv_get_dirty_log_radix(struct kvm *kvm,
> struct kvm_memory_slot *memslot, unsigned long *map);
> +extern void kvmppc_radix_flush_memslot(struct kvm *kvm,
> + const struct kvm_memory_slot *memslot);
> extern int kvmhv_get_rmmu_info(struct kvm *kvm, struct kvm_ppc_rmmu_info *info);
>
> /* XXX remove this export when load_last_inst() is generic */
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index a18afda..6f2d2fb 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -899,11 +899,12 @@ void kvmppc_core_flush_memslot_hv(struct kvm *kvm,
>
> gfn = memslot->base_gfn;
> rmapp = memslot->arch.rmap;
> + if (kvm_is_radix(kvm)) {
> + kvmppc_radix_flush_memslot(kvm, memslot);
> + return;
> + }
> +
> for (n = memslot->npages; n; --n, ++gfn) {
> - if (kvm_is_radix(kvm)) {
> - kvm_unmap_radix(kvm, memslot, gfn);
> - continue;
> - }
> /*
> * Testing the present bit without locking is OK because
> * the memslot has been marked invalid already, and hence
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> index 52711eb..d675ad9 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> @@ -958,6 +958,26 @@ long kvmppc_hv_get_dirty_log_radix(struct kvm *kvm,
> return 0;
> }
>
> +void kvmppc_radix_flush_memslot(struct kvm *kvm,
> + const struct kvm_memory_slot *memslot)
> +{
> + unsigned long n;
> + pte_t *ptep;
> + unsigned long gpa;
> + unsigned int shift;
> +
> + gpa = memslot->base_gfn << PAGE_SHIFT;
> + spin_lock(&kvm->mmu_lock);
> + for (n = memslot->npages; n; --n) {
> + ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
> + if (ptep && pte_present(*ptep))
> + kvmppc_unmap_pte(kvm, ptep, gpa, shift, memslot,
> + kvm->arch.lpid);
> + gpa += PAGE_SIZE;
> + }
> + spin_unlock(&kvm->mmu_lock);
> +}
> +
> static void add_rmmu_ap_encoding(struct kvm_ppc_rmmu_info *info,
> int psize, int *indexp)
> {
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index f4fbb7b5..074ff5b 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4384,6 +4384,23 @@ static void kvmppc_core_commit_memory_region_hv(struct kvm *kvm,
> */
> if (npages)
> atomic64_inc(&kvm->arch.mmio_update);
> +
> + /*
> + * For change == KVM_MR_MOVE or KVM_MR_DELETE, higher levels
> + * have already called kvm_arch_flush_shadow_memslot() to
> + * flush shadow mappings. For KVM_MR_CREATE we have no
> + * previous mappings. So the only case to handle is
> + * KVM_MR_FLAGS_ONLY when the KVM_MEM_LOG_DIRTY_PAGES bit
> + * has been changed.
> + * For radix guests, we flush on setting KVM_MEM_LOG_DIRTY_PAGES
> + * to get rid of any THP PTEs in the partition-scoped page tables
> + * so we can track dirtiness at the page level; we flush when
> + * clearing KVM_MEM_LOG_DIRTY_PAGES so that we can go back to
> + * using THP PTEs.
> + */
> + if (change == KVM_MR_FLAGS_ONLY && kvm_is_radix(kvm) &&
> + ((new->flags ^ old->flags) & KVM_MEM_LOG_DIRTY_PAGES))
> + kvmppc_radix_flush_memslot(kvm, old);
> }
>
> /*
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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