On Fri, 27 Jan 2023 11:29:12 +0000 Steven Price <steven.price@xxxxxxx> wrote: > Pages can only be populated/destroyed on the RMM at the 4KB granule, > this requires creating the full depth of RTTs. However if the pages are > going to be combined into a 4MB huge page the last RTT is only > temporarily needed. Similarly when freeing memory the huge page must be > temporarily split requiring temporary usage of the full depth oF RTTs. > > To avoid needing to perform a temporary allocation and delegation of a > page for this purpose we keep a spare delegated page around. In > particular this avoids the need for memory allocation while destroying > the realm guest. > > Signed-off-by: Steven Price <steven.price@xxxxxxx> > --- > arch/arm64/include/asm/kvm_rme.h | 3 +++ > arch/arm64/kvm/rme.c | 6 ++++++ > 2 files changed, 9 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h > index 055a22accc08..a6318af3ed11 100644 > --- a/arch/arm64/include/asm/kvm_rme.h > +++ b/arch/arm64/include/asm/kvm_rme.h > @@ -21,6 +21,9 @@ struct realm { > void *rd; > struct realm_params *params; > > + /* A spare already delegated page */ > + phys_addr_t spare_page; > + > unsigned long num_aux; > unsigned int vmid; > unsigned int ia_bits; > diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c > index 9f8c5a91b8fc..0c9d70e4d9e6 100644 > --- a/arch/arm64/kvm/rme.c > +++ b/arch/arm64/kvm/rme.c > @@ -148,6 +148,7 @@ static int realm_create_rd(struct kvm *kvm) > } > > realm->rd = rd; > + realm->spare_page = PHYS_ADDR_MAX; > realm->ia_bits = VTCR_EL2_IPA(kvm->arch.vtcr); > > if (WARN_ON(rmi_rec_aux_count(rd_phys, &realm->num_aux))) { > @@ -357,6 +358,11 @@ void kvm_destroy_realm(struct kvm *kvm) > free_page((unsigned long)realm->rd); > realm->rd = NULL; > } > + if (realm->spare_page != PHYS_ADDR_MAX) { > + if (!WARN_ON(rmi_granule_undelegate(realm->spare_page))) > + free_page((unsigned long)phys_to_virt(realm->spare_page)); Will the page be leaked (not usable for host and realms) if the undelegate failed? If yes, better at least put a comment. > + realm->spare_page = PHYS_ADDR_MAX; > + } > > pgd_sz = kvm_pgd_pages(pgt->ia_bits, pgt->start_level); > for (i = 0; i < pgd_sz; i++) {