On Thu, May 6, 2021 at 11:43 AM Ben Gardon <bgardon@xxxxxxxxxx> wrote:
>
> Add a field to control whether new memslots should have rmaps allocated
> for them. As of this change, it's not safe to skip allocating rmaps, so
> the field is always set to allocate rmaps. Future changes will make it
> safe to operate without rmaps, using the TDP MMU. Then further changes
> will allow the rmaps to be allocated lazily when needed for nested
> oprtation.
>
> No functional change expected.
>
> Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 8 ++++++++
> arch/x86/kvm/mmu/mmu.c | 2 ++
> arch/x86/kvm/x86.c | 18 +++++++++++++-----
> 3 files changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index ad22d4839bcc..00065f9bbc5e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1122,6 +1122,12 @@ struct kvm_arch {
> */
> spinlock_t tdp_mmu_pages_lock;
> #endif /* CONFIG_X86_64 */
> +
> + /*
> + * If set, rmaps have been allocated for all memslots and should be
> + * allocated for any newly created or modified memslots.
> + */
> + bool memslots_have_rmaps;
> };
>
> struct kvm_vm_stat {
> @@ -1853,4 +1859,6 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
>
> int kvm_cpu_dirty_log_size(void);
>
> +inline bool kvm_memslots_have_rmaps(struct kvm *kvm);
Woops, this shouldn't be marked inline as it creates build problems
for the next patch with some configs.
> +
> #endif /* _ASM_X86_KVM_HOST_H */
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 930ac8a7e7c9..8761b4925755 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5469,6 +5469,8 @@ void kvm_mmu_init_vm(struct kvm *kvm)
>
> kvm_mmu_init_tdp_mmu(kvm);
>
> + kvm->arch.memslots_have_rmaps = true;
> +
> node->track_write = kvm_mmu_pte_write;
> node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
> kvm_page_track_register_notifier(kvm, node);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fc32a7dbe4c4..d7a40ce342cc 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10868,7 +10868,13 @@ static int alloc_memslot_rmap(struct kvm_memory_slot *slot,
> return -ENOMEM;
> }
>
> -static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
> +bool kvm_memslots_have_rmaps(struct kvm *kvm)
> +{
> + return kvm->arch.memslots_have_rmaps;
> +}
> +
> +static int kvm_alloc_memslot_metadata(struct kvm *kvm,
> + struct kvm_memory_slot *slot,
> unsigned long npages)
> {
> int i;
> @@ -10881,9 +10887,11 @@ static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
> */
> memset(&slot->arch, 0, sizeof(slot->arch));
>
> - r = alloc_memslot_rmap(slot, npages);
> - if (r)
> - return r;
> + if (kvm_memslots_have_rmaps(kvm)) {
> + r = alloc_memslot_rmap(slot, npages);
> + if (r)
> + return r;
> + }
>
> for (i = 1; i < KVM_NR_PAGE_SIZES; ++i) {
> struct kvm_lpage_info *linfo;
> @@ -10954,7 +10962,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
> enum kvm_mr_change change)
> {
> if (change == KVM_MR_CREATE || change == KVM_MR_MOVE)
> - return kvm_alloc_memslot_metadata(memslot,
> + return kvm_alloc_memslot_metadata(kvm, memslot,
> mem->memory_size >> PAGE_SHIFT);
> return 0;
> }
> --
> 2.31.1.607.g51e8a6a459-goog
>
