linux-kernel - [PATCH 2/2] KVM: arm64: Allow only the specified FF-A calls to be forwarded to TZ

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Date: Fri, 22 Mar 2024 12:43:03 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: catalin.marinas@....com, james.morse@....com, jean-philippe@...aro.org, 
	maz@...nel.org, oliver.upton@...ux.dev, qperret@...gle.com, 
	qwandor@...gle.com, sebastianene@...gle.com, suzuki.poulose@....com, 
	tabba@...gle.com, will@...nel.org, yuzenghui@...wei.com
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: [PATCH 2/2] KVM: arm64: Allow only the specified FF-A calls to be
 forwarded to TZ

The previous logic used a deny list to filter the FF-A calls. Because of
this, some of the calls escaped the check and they were forwarded by
default to Trustzone. (eg. FFA_MSG_SEND_DIRECT_REQ was denied but the 64
bit version of the call was not).
Modify the logic to use an allowlist and allow only the calls specified in
the filter function to be proxied to TZ from the hypervisor.

Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 46 +++++++++++++++++------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 320f2eaa14a9..fc4f04209618 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -580,35 +580,35 @@ static void do_ffa_mem_reclaim(struct arm_smccc_res *res,
 		ffa_to_smccc_res(res, ret);
 }
 
-/*
- * Is a given FFA function supported, either by forwarding on directly
- * or by handling at EL2?
- */
 static bool ffa_call_supported(u64 func_id)
 {
 	switch (func_id) {
-	/* Unsupported memory management calls */
-	case FFA_FN64_MEM_RETRIEVE_REQ:
-	case FFA_MEM_RETRIEVE_RESP:
-	case FFA_MEM_RELINQUISH:
-	case FFA_MEM_OP_PAUSE:
-	case FFA_MEM_OP_RESUME:
-	case FFA_MEM_FRAG_RX:
-	case FFA_FN64_MEM_DONATE:
-	/* Indirect message passing via RX/TX buffers */
-	case FFA_MSG_SEND:
-	case FFA_MSG_POLL:
-	case FFA_MSG_WAIT:
-	/* 32-bit variants of 64-bit calls */
+	/* Discovery functions */
+	case FFA_FEATURES:
+	case FFA_ID_GET:
+	case FFA_VERSION:
+	case FFA_PARTITION_INFO_GET:
+
+	/* Memory management calls */
+	case FFA_FN64_RXTX_MAP:
+	case FFA_RXTX_UNMAP:
+	case FFA_MEM_SHARE:
+	case FFA_FN64_MEM_SHARE:
+	case FFA_MEM_RECLAIM:
+	case FFA_MEM_LEND:
+	case FFA_FN64_MEM_LEND:
+	case FFA_MEM_FRAG_TX:
+
+	/* State management */
+	case FFA_RUN:
+
+	/* Message passing */
 	case FFA_MSG_SEND_DIRECT_REQ:
-	case FFA_MSG_SEND_DIRECT_RESP:
-	case FFA_RXTX_MAP:
-	case FFA_MEM_DONATE:
-	case FFA_MEM_RETRIEVE_REQ:
-		return false;
+	case FFA_FN64_MSG_SEND_DIRECT_REQ:
+		return true;
 	}
 
-	return true;
+	return false;
 }
 
 static bool do_ffa_features(struct arm_smccc_res *res,
-- 
2.44.0.396.g6e790dbe36-goog