Hi Steven
On 12/04/2024 09:42, Steven Price 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
minor nit: 2MB huge page.
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 | 5 +++++
arch/arm64/kvm/rme.c | 8 ++++++++
2 files changed, 13 insertions(+)
diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
index cf8cc4d30364..fba85e9ce3ae 100644
--- a/arch/arm64/include/asm/kvm_rme.h
+++ b/arch/arm64/include/asm/kvm_rme.h
@@ -50,6 +50,9 @@ enum realm_state {
* @state: The lifetime state machine for the realm
* @rd: Kernel mapping of the Realm Descriptor (RD)
* @params: Parameters for the RMI_REALM_CREATE command
+ * @spare_page: A physical page that has been delegated to the Realm world but
+ * is otherwise free. Used to avoid temporary allocation during
+ * RTT operations.
* @num_aux: The number of auxiliary pages required by the RMM
* @vmid: VMID to be used by the RMM for the realm
* @ia_bits: Number of valid Input Address bits in the IPA
@@ -60,6 +63,8 @@ struct realm {
void *rd;
struct realm_params *params;
+ 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 658d14e8d87d..9652ec6ab2fd 100644
--- a/arch/arm64/kvm/rme.c
+++ b/arch/arm64/kvm/rme.c
@@ -103,6 +103,7 @@ static int realm_create_rd(struct kvm *kvm)
}
realm->rd = rd;
+ realm->spare_page = PHYS_ADDR_MAX;
if (WARN_ON(rmi_rec_aux_count(rd_phys, &realm->num_aux))) {
WARN_ON(rmi_realm_destroy(rd_phys));
@@ -283,6 +284,13 @@ void kvm_destroy_realm(struct kvm *kvm)
rme_vmid_release(realm->vmid);
+ if (realm->spare_page != PHYS_ADDR_MAX) {
+ /* Leak the page if the undelegate fails */
+ if (!WARN_ON(rmi_granule_undelegate(realm->spare_page)))
+ free_page((unsigned long)phys_to_virt(realm->spare_page));
+ realm->spare_page = PHYS_ADDR_MAX;
+ }
+
for (i = 0; i < pgt->pgd_pages; i++) {
phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i * PAGE_SIZE;
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
