On Fri, Dec 13, 2024 at 02:57:06PM -0500, Paolo Bonzini wrote:
> Teach the MMU notifier callbacks how to check kvm_gfn_range.process to
> filter which KVM MMU root types to operate on.
>
> The private GPAs are backed by guest memfd. Such memory is not subjected
> to MMU notifier callbacks because it can't be mapped into the host user
> address space. Now kvm_gfn_range conveys info about which root to operate
> on. Enhance the callback to filter the root page table type.
>
> The KVM MMU notifier comes down to two functions.
> kvm_tdp_mmu_unmap_gfn_range() and __kvm_tdp_mmu_age_gfn_range():
> - invalidate_range_start() calls kvm_tdp_mmu_unmap_gfn_range()
> - invalidate_range_end() doesn't call into arch code
> - the other callbacks call __kvm_tdp_mmu_age_gfn_range()
>
> For VM's without a private/shared split in the EPT, all operations
> should target the normal(direct) root.
>
> With the switch from for_each_tdp_mmu_root() to
> __for_each_tdp_mmu_root() in kvm_tdp_mmu_handle_gfn(), there are no
> longer any users of for_each_tdp_mmu_root(). Remove it.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Message-ID: <20240718211230.1492011-14-rick.p.edgecombe@xxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/tdp_mmu.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index d17a3cf1596d..9a004c999a28 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -193,9 +193,6 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
> !tdp_mmu_root_match((_root), (_types)))) { \
> } else
>
> -#define for_each_tdp_mmu_root(_kvm, _root, _as_id) \
> - __for_each_tdp_mmu_root(_kvm, _root, _as_id, KVM_ALL_ROOTS)
> -
> #define for_each_valid_tdp_mmu_root(_kvm, _root, _as_id) \
> __for_each_tdp_mmu_root(_kvm, _root, _as_id, KVM_VALID_ROOTS)
>
> @@ -1172,12 +1169,16 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> return ret;
> }
>
> +/* Used by mmu notifier via kvm_unmap_gfn_range() */
> bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range,
> bool flush)
> {
> + enum kvm_tdp_mmu_root_types types;
> struct kvm_mmu_page *root;
>
> - __for_each_tdp_mmu_root_yield_safe(kvm, root, range->slot->as_id, KVM_ALL_ROOTS)
> + types = kvm_gfn_range_filter_to_root_types(kvm, range->attr_filter) | KVM_INVALID_ROOTS;
Just curious:
though adding KVM_INVALID_ROOTS matches the old KVM_ALL_ROOTS, why do we need
to unmap an invalid root?
> +
> + __for_each_tdp_mmu_root_yield_safe(kvm, root, range->slot->as_id, types)
> flush = tdp_mmu_zap_leafs(kvm, root, range->start, range->end,
> range->may_block, flush);
>
> @@ -1217,17 +1218,21 @@ static bool __kvm_tdp_mmu_age_gfn_range(struct kvm *kvm,
> struct kvm_gfn_range *range,
> bool test_only)
> {
> + enum kvm_tdp_mmu_root_types types;
> struct kvm_mmu_page *root;
> struct tdp_iter iter;
> bool ret = false;
>
> + types = kvm_gfn_range_filter_to_root_types(kvm, range->attr_filter);
> +
> /*
> * Don't support rescheduling, none of the MMU notifiers that funnel
> * into this helper allow blocking; it'd be dead, wasteful code. Note,
> * this helper must NOT be used to unmap GFNs, as it processes only
> * valid roots!
> */
> - for_each_valid_tdp_mmu_root(kvm, root, range->slot->as_id) {
> + WARN_ON(types & ~KVM_VALID_ROOTS);
> + __for_each_tdp_mmu_root(kvm, root, range->slot->as_id, types) {
> guard(rcu)();
>
> tdp_root_for_each_leaf_pte(iter, kvm, root, range->start, range->end) {
> --
> 2.43.5
>
>
