[PATCH v2 05/10] KVM: arm64: Add FF-A helpers to share/unshare memory with secure world

Will Deacon
2023-04-19T12:22:16Z

Extend pKVM's memory protection code so that we can update the host's
stage-2 page-table to track pages shared with secure world by the host
using FF-A and prevent those pages from being mapped into a guest.

Co-developed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 3 +
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 68 +++++++++++++++++++
2 files changed, 71 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index b7bdbe63deed..0972faccc2af 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -57,6 +57,7 @@ extern struct host_mmu host_mmu;
enum pkvm_component_id {
PKVM_ID_HOST,
PKVM_ID_HYP,
+ PKVM_ID_FFA,
};

extern unsigned long hyp_nr_cpus;
@@ -66,6 +67,8 @@ int __pkvm_host_share_hyp(u64 pfn);
int __pkvm_host_unshare_hyp(u64 pfn);
int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
+int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
+int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);

bool addr_is_memory(phys_addr_t phys);
int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 552653fa18be..e721fba3bb33 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -835,6 +835,13 @@ static int check_share(struct pkvm_mem_share *share)
case PKVM_ID_HYP:
ret = hyp_ack_share(completer_addr, tx, share->completer_prot);
break;
+ case PKVM_ID_FFA:
+ /*
+ * We only check the host; the secure side will check the other
+ * end when we forward the FFA call.
+ */
+ ret = 0;
+ break;
default:
ret = -EINVAL;
}
@@ -863,6 +870,13 @@ static int __do_share(struct pkvm_mem_share *share)
case PKVM_ID_HYP:
ret = hyp_complete_share(completer_addr, tx, share->completer_prot);
break;
+ case PKVM_ID_FFA:
+ /*
+ * We're not responsible for any secure page-tables, so there's
+ * nothing to do here.
+ */
+ ret = 0;
+ break;
default:
ret = -EINVAL;
}
@@ -911,6 +925,10 @@ static int check_unshare(struct pkvm_mem_share *share)
case PKVM_ID_HYP:
ret = hyp_ack_unshare(completer_addr, tx);
break;
+ case PKVM_ID_FFA:
+ /* See check_share() */
+ ret = 0;
+ break;
default:
ret = -EINVAL;
}
@@ -939,6 +957,10 @@ static int __do_unshare(struct pkvm_mem_share *share)
case PKVM_ID_HYP:
ret = hyp_complete_unshare(completer_addr, tx);
break;
+ case PKVM_ID_FFA:
+ /* See __do_share() */
+ ret = 0;
+ break;
default:
ret = -EINVAL;
}
@@ -1228,3 +1250,49 @@ void hyp_unpin_shared_mem(void *from, void *to)
hyp_unlock_component();
host_unlock_component();
}
+
+int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages)
+{
+ int ret;
+ struct pkvm_mem_share share = {
+ .tx = {
+ .nr_pages = nr_pages,
+ .initiator = {
+ .id = PKVM_ID_HOST,
+ .addr = hyp_pfn_to_phys(pfn),
+ },
+ .completer = {
+ .id = PKVM_ID_FFA,
+ },
+ },
+ };
+
+ host_lock_component();
+ ret = do_share(&share);
+ host_unlock_component();
+
+ return ret;
+}
+
+int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages)
+{
+ int ret;
+ struct pkvm_mem_share share = {
+ .tx = {
+ .nr_pages = nr_pages,
+ .initiator = {
+ .id = PKVM_ID_HOST,
+ .addr = hyp_pfn_to_phys(pfn),
+ },
+ .completer = {
+ .id = PKVM_ID_FFA,
+ },
+ },
+ };
+
+ host_lock_component();
+ ret = do_unshare(&share);
+ host_unlock_component();
+
+ return ret;