[PATCH v2 3/4] KVM: arm64: Map the hypervisor FF-A buffers on ffa init

Sebastian Ene
2025-02-27T19:42:35Z

Map the hypervisor's buffers irrespective to the host and return
a linux error code from the FF-A error code on failure. Remove
the unmap ff-a buffers calls from the hypervisor as it will
never be called.
Prevent the host from using FF-A directly with Trustzone
if the hypervisor could not map its own buffers.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
arch/arm64/kvm/hyp/nvhe/ffa.c | 46 +++++++++++++----------------------
1 file changed, 17 insertions(+), 29 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 6df6131f1107..861f24de97cb 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -69,6 +69,7 @@ static struct kvm_ffa_buffers hyp_buffers;
static struct kvm_ffa_buffers host_buffers;
static u32 hyp_ffa_version;
static bool has_version_negotiated;
+static bool has_ffa_supported;
static DEFINE_HYP_SPINLOCK(version_lock);

static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
@@ -111,30 +112,18 @@ static bool is_ffa_call(u64 func_id)
ARM_SMCCC_FUNC_NUM(func_id) <= FFA_MAX_FUNC_NUM;
}

-static int ffa_map_hyp_buffers(u64 ffa_page_count)
+static int ffa_map_hyp_buffers(void)
{
struct arm_smccc_res res;

arm_smccc_1_1_smc(FFA_FN64_RXTX_MAP,
hyp_virt_to_phys(hyp_buffers.tx),
hyp_virt_to_phys(hyp_buffers.rx),
- ffa_page_count,
+ KVM_FFA_MBOX_NR_PAGES,
0, 0, 0, 0,
&res);

- return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
-}
-
-static int ffa_unmap_hyp_buffers(void)
-{
- struct arm_smccc_res res;
-
- arm_smccc_1_1_smc(FFA_RXTX_UNMAP,
- HOST_FFA_ID,
- 0, 0, 0, 0, 0, 0,
- &res);
-
- return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
+ return res.a0 == FFA_SUCCESS ? 0 : ffa_to_linux_errno(res.a2);
}

static void ffa_mem_frag_tx(struct arm_smccc_res *res, u32 handle_lo,
@@ -213,18 +202,10 @@ static void do_ffa_rxtx_map(struct arm_smccc_res *res,
goto out_unlock;
}

- /*
- * Map our hypervisor buffers into the SPMD before mapping and
- * pinning the host buffers in our own address space.
- */
- ret = ffa_map_hyp_buffers(npages);
- if (ret)
- goto out_unlock;
-
ret = __pkvm_host_share_hyp(hyp_phys_to_pfn(tx));
if (ret) {
ret = FFA_RET_INVALID_PARAMETERS;
- goto err_unmap;
+ goto out_unlock;
}

ret = __pkvm_host_share_hyp(hyp_phys_to_pfn(rx));
@@ -262,8 +243,6 @@ static void do_ffa_rxtx_map(struct arm_smccc_res *res,
__pkvm_host_unshare_hyp(hyp_phys_to_pfn(rx));
err_unshare_tx:
__pkvm_host_unshare_hyp(hyp_phys_to_pfn(tx));
-err_unmap:
- ffa_unmap_hyp_buffers();
goto out_unlock;
}

@@ -291,9 +270,6 @@ static void do_ffa_rxtx_unmap(struct arm_smccc_res *res,
hyp_unpin_shared_mem(host_buffers.rx, host_buffers.rx + 1);
WARN_ON(__pkvm_host_unshare_hyp(hyp_virt_to_pfn(host_buffers.rx)));
host_buffers.rx = NULL;
-
- ffa_unmap_hyp_buffers();
-
out_unlock:
hyp_spin_unlock(&host_buffers.lock);
out:
@@ -809,6 +785,11 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
if (!is_ffa_call(func_id))
return false;

+ if (!has_ffa_supported) {
+ ffa_to_smccc_error(&res, FFA_RET_NOT_SUPPORTED);
+ goto out_handled;
+ }
+
if (!has_version_negotiated && func_id != FFA_VERSION) {
ffa_to_smccc_error(&res, FFA_RET_INVALID_PARAMETERS);
goto out_handled;
@@ -861,6 +842,7 @@ int hyp_ffa_init(void *pages)
{
struct arm_smccc_res res;
void *tx, *rx;
+ int ret;

if (kvm_host_psci_config.smccc_version < ARM_SMCCC_VERSION_1_2)
return 0;
@@ -911,5 +893,11 @@ int hyp_ffa_init(void *pages)
.lock = __HYP_SPIN_LOCK_UNLOCKED,
};

+ /* Map our hypervisor buffers into the SPMD */
+ ret = ffa_map_hyp_buffers();
+ if (ret)
+ return ret;
+
+ has_ffa_supported = true;
return 0;
}
--
2.48.1.711.g2feabab25a-goog