[PATCH v5 0/2] KVM: arm64: Support FF-A direct messaging interfaces

[PATCH v5 0/2] KVM: arm64: Support FF-A direct messaging interfaces

[Per Larsen via B4 Relay]

Support FFA_MSG_SEND_DIRECT_REQ unconditionally.
Support FFA_MSG_SEND_DIRECT_REQ2 if hypervisor negotiated version 1.2+.

Framework messages (FF-A control plane) are filtered out. For
FFA_MSG_SEND_DIRECT_REQ, we look at flags in w2. Messages using the REQ2
interface are always partition messages.

The second patch was part of a previous patch set [0] but was dropped
since the use case was unclear. A clear use case has now appeared: use
TPM device with CRB over FF-A when kernel boots with pkvm [1].

Tested by booting Android under QEMU.

Best Regards,
Per

[0]: https://lore.kernel.org/all/20250730-virtio-msg-ffa-v9-0-7f1b55c8d149@google.com/
[1]: https://lore.kernel.org/all/20251027191729.1704744-1-yeoreum.yun@arm.com/
 

Signed-off-by: Per Larsen <perlarsen@google.com>
---
Changes in v5:
- 1/2: do_ffa_direct_msg: validate that sender is HOST_FFA_ID.
- Link to v4: https://lore.kernel.org/r/20260109-host-direct-messages-v4-0-95da4221d186@google.com

Changes in v4:
- 1/2: do_ffa_direct_msg: check that flag in w2 is zero; drop unused vm_handle parameter.
- 2/2: ffa_call_supported: simplify logic by reordering cases.
-      do_ffa_direct_msg: switch polarity of check and update comment.
- Link to v3: https://lore.kernel.org/r/20251119-host-direct-messages-v3-0-c74d04944b26@google.com

Changes in v3:
- Filter out framework messages as suggested by Will Deacon. Update cover letter accordingly.
- Update trailers: Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
- Link to v2: https://lore.kernel.org/r/20251030-host-direct-messages-v2-0-9f27cef36730@google.com

Changes in v2:
- 1/2: Drop support for FFA_ID_GET interface in host handler.
- Link to v1: https://lore.kernel.org/r/20251030-host-direct-messages-v1-0-463e57871c8f@google.com

---
Per Larsen (1):
      KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in host handler

Sebastian Ene (1):
      KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler

 arch/arm64/kvm/hyp/nvhe/ffa.c | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)
---
base-commit: 6c790212c588fddeb0d852f2790840753bb604b1
change-id: 20251029-host-direct-messages-5201d7f55abd

Best regards,
-- 
Per Larsen <perlarsen@google.com>

[PATCH v5 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler

[Per Larsen via B4 Relay]

From: Sebastian Ene <sebastianene@google.com>

Allow direct messages to be forwarded from the host. The host should
not be sending framework messages so they are filtered out.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Per Larsen <perlarsen@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index f731cc4c3f280a32acccca0de92b9ac6c8e05602..9967916278a7ca051500946ef2fcfe7bb40e0e8d 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -862,6 +862,28 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
 	hyp_spin_unlock(&host_buffers.lock);
 }
 
+static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
+			      struct kvm_cpu_context *ctxt,
+			      u64 vm_handle)
+{
+	DECLARE_REG(u32, flags, ctxt, 2);
+
+	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
+
+	if (vm_handle != HOST_FFA_ID) {
+		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
+	/* filter out framework messages and validate SBZ/MBZ bits */
+	if (flags) {
+		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
+	arm_smccc_1_2_smc(args, res);
+}
+
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 {
 	struct arm_smccc_1_2_regs res;
@@ -920,6 +942,10 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 	case FFA_PARTITION_INFO_GET:
 		do_ffa_part_get(&res, host_ctxt);
 		goto out_handled;
+	case FFA_MSG_SEND_DIRECT_REQ:
+	case FFA_FN64_MSG_SEND_DIRECT_REQ:
+		do_ffa_direct_msg(&res, host_ctxt, HOST_FFA_ID);
+		goto out_handled;
 	}
 
 	if (ffa_call_supported(func_id))

-- 
2.52.0.457.g6b5491de43-goog

Re: [PATCH v5 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler

[Will Deacon]

Per,

On Wed, Jan 21, 2026 at 08:27:12AM +0000, Per Larsen via B4 Relay wrote:
> From: Sebastian Ene <sebastianene@google.com>
> 
> Allow direct messages to be forwarded from the host. The host should
> not be sending framework messages so they are filtered out.
> 
> Signed-off-by: Sebastian Ene <sebastianene@google.com>
> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
> Signed-off-by: Per Larsen <perlarsen@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index f731cc4c3f280a32acccca0de92b9ac6c8e05602..9967916278a7ca051500946ef2fcfe7bb40e0e8d 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -862,6 +862,28 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
>  	hyp_spin_unlock(&host_buffers.lock);
>  }
>  
> +static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
> +			      struct kvm_cpu_context *ctxt,
> +			      u64 vm_handle)
> +{
> +	DECLARE_REG(u32, flags, ctxt, 2);
> +
> +	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
> +
> +	if (vm_handle != HOST_FFA_ID) {
> +		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}

Sorry, but this isn't what I had in mind. 'vm_handle' is just a local
variable and the only caller passes HOST_FFA_ID, so this isn't really
achieving anything.

What you had in v4 dropped the 'vm_handle' argument entirely, which I
think is the right thing to do. However, the FF-A spec encodes the sender
ID in bits 31:16 of register W1 and so _that_ is what I think we should
be checking because _that_ is what the receiver will see.

Honestly, we could avoid quite a lot of these review cycles if you
actually replied to my emails on the list instead of just responding
with a new patch series each time. It's supposed to be a technical
discussion...

Will

Re: [PATCH v5 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler

[Per Larsen]

On 1/23/26 4:55 AM, Will Deacon wrote:
> Per,
> 
> On Wed, Jan 21, 2026 at 08:27:12AM +0000, Per Larsen via B4 Relay wrote:
>> From: Sebastian Ene <sebastianene@google.com>
>>
>> Allow direct messages to be forwarded from the host. The host should
>> not be sending framework messages so they are filtered out.
>>
>> Signed-off-by: Sebastian Ene <sebastianene@google.com>
>> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
>> Signed-off-by: Per Larsen <perlarsen@google.com>
>> ---
>>   arch/arm64/kvm/hyp/nvhe/ffa.c | 26 ++++++++++++++++++++++++++
>>   1 file changed, 26 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
>> index f731cc4c3f280a32acccca0de92b9ac6c8e05602..9967916278a7ca051500946ef2fcfe7bb40e0e8d 100644
>> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
>> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
>> @@ -862,6 +862,28 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
>>   	hyp_spin_unlock(&host_buffers.lock);
>>   }
>>   
>> +static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
>> +			      struct kvm_cpu_context *ctxt,
>> +			      u64 vm_handle)
>> +{
>> +	DECLARE_REG(u32, flags, ctxt, 2);
>> +
>> +	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
>> +
>> +	if (vm_handle != HOST_FFA_ID) {
>> +		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
>> +		return;
>> +	}
> 
> Sorry, but this isn't what I had in mind. 'vm_handle' is just a local
> variable and the only caller passes HOST_FFA_ID, so this isn't really
> achieving anything.
> 
> What you had in v4 dropped the 'vm_handle' argument entirely, which I
> think is the right thing to do. However, the FF-A spec encodes the sender
> ID in bits 31:16 of register W1 and so _that_ is what I think we should
> be checking because _that_ is what the receiver will see.

I should have read your feedback more closely and checked against the 
spec. I will add a new mask for bits 31:16 to check sender ID against
HOST_FFA_ID. Sorry to waste a review cycle and your attention on this.

> Honestly, we could avoid quite a lot of these review cycles if you
> actually replied to my emails on the list instead of just responding
> with a new patch series each time. It's supposed to be a technical
> discussion...

Acknowledged; will do! Apologies for the very late reply.

[PATCH v5 2/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in host handler

[Per Larsen via B4 Relay]

From: Per Larsen <perlarsen@google.com>

FF-A 1.2 adds the DIRECT_REQ2 messaging interface which is similar to
the existing FFA_MSG_SEND_DIRECT_{REQ,RESP} functions and can use the
existing handler function. Add support for FFA_MSG_SEND_DIRECT_REQ2 in
the host ffa handler.

Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Per Larsen <perlarsen@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 9967916278a7ca051500946ef2fcfe7bb40e0e8d..17b92f7faaf68e56aef0ebbe58710b7485a87231 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -684,11 +684,12 @@ static bool ffa_call_supported(u64 func_id)
 	case FFA_NOTIFICATION_GET:
 	case FFA_NOTIFICATION_INFO_GET:
 	/* Optional interfaces added in FF-A 1.2 */
-	case FFA_MSG_SEND_DIRECT_REQ2:		/* Optional per 7.5.1 */
 	case FFA_MSG_SEND_DIRECT_RESP2:		/* Optional per 7.5.1 */
 	case FFA_CONSOLE_LOG:			/* Optional per 13.1: not in Table 13.1 */
 	case FFA_PARTITION_INFO_GET_REGS:	/* Optional for virtual instances per 13.1 */
 		return false;
+	case FFA_MSG_SEND_DIRECT_REQ2:		/* Optional per 7.5.1 */
+		return hyp_ffa_version >= FFA_VERSION_1_2;
 	}
 
 	return true;
@@ -866,6 +867,7 @@ static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
 			      struct kvm_cpu_context *ctxt,
 			      u64 vm_handle)
 {
+	DECLARE_REG(u64, func_id, ctxt, 0);
 	DECLARE_REG(u32, flags, ctxt, 2);
 
 	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
@@ -875,8 +877,12 @@ static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
 		return;
 	}
 
-	/* filter out framework messages and validate SBZ/MBZ bits */
-	if (flags) {
+	/*
+	 * filter out framework messages and validate SBZ/MBZ flag bits.
+	 * FFA_MSG_SEND_DIRECT_REQ2 implies flag-less partition message.
+	 */
+	if ((func_id == FFA_MSG_SEND_DIRECT_REQ ||
+	     func_id == FFA_FN64_MSG_SEND_DIRECT_REQ) && flags) {
 		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
 		return;
 	}
@@ -942,6 +948,10 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 	case FFA_PARTITION_INFO_GET:
 		do_ffa_part_get(&res, host_ctxt);
 		goto out_handled;
+	case FFA_MSG_SEND_DIRECT_REQ2:
+		if (!ffa_call_supported(func_id))
+			goto out_not_supported;
+		fallthrough;
 	case FFA_MSG_SEND_DIRECT_REQ:
 	case FFA_FN64_MSG_SEND_DIRECT_REQ:
 		do_ffa_direct_msg(&res, host_ctxt, HOST_FFA_ID);
@@ -951,6 +961,7 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 	if (ffa_call_supported(func_id))
 		return false; /* Pass through */
 
+out_not_supported:
 	ffa_to_smccc_error(&res, FFA_RET_NOT_SUPPORTED);
 out_handled:
 	ffa_set_retval(host_ctxt, &res);

-- 
2.52.0.457.g6b5491de43-goog

Re: [PATCH v5 0/2] KVM: arm64: Support FF-A direct messaging interfaces

[Yeoreum Yun]

Hi Per,

May I ask how this patch is progressing?

Thanks!

> Support FFA_MSG_SEND_DIRECT_REQ unconditionally.
> Support FFA_MSG_SEND_DIRECT_REQ2 if hypervisor negotiated version 1.2+.
> 
> Framework messages (FF-A control plane) are filtered out. For
> FFA_MSG_SEND_DIRECT_REQ, we look at flags in w2. Messages using the REQ2
> interface are always partition messages.
> 
> The second patch was part of a previous patch set [0] but was dropped
> since the use case was unclear. A clear use case has now appeared: use
> TPM device with CRB over FF-A when kernel boots with pkvm [1].
> 
> Tested by booting Android under QEMU.
> 
> Best Regards,
> Per
> 
> [0]: https://lore.kernel.org/all/20250730-virtio-msg-ffa-v9-0-7f1b55c8d149@google.com/
> [1]: https://lore.kernel.org/all/20251027191729.1704744-1-yeoreum.yun@arm.com/
>  
> 
> Signed-off-by: Per Larsen <perlarsen@google.com>
> ---
> Changes in v5:
> - 1/2: do_ffa_direct_msg: validate that sender is HOST_FFA_ID.
> - Link to v4: https://lore.kernel.org/r/20260109-host-direct-messages-v4-0-95da4221d186@google.com
> 
> Changes in v4:
> - 1/2: do_ffa_direct_msg: check that flag in w2 is zero; drop unused vm_handle parameter.
> - 2/2: ffa_call_supported: simplify logic by reordering cases.
> -      do_ffa_direct_msg: switch polarity of check and update comment.
> - Link to v3: https://lore.kernel.org/r/20251119-host-direct-messages-v3-0-c74d04944b26@google.com
> 
> Changes in v3:
> - Filter out framework messages as suggested by Will Deacon. Update cover letter accordingly.
> - Update trailers: Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
> - Link to v2: https://lore.kernel.org/r/20251030-host-direct-messages-v2-0-9f27cef36730@google.com
> 
> Changes in v2:
> - 1/2: Drop support for FFA_ID_GET interface in host handler.
> - Link to v1: https://lore.kernel.org/r/20251030-host-direct-messages-v1-0-463e57871c8f@google.com
> 
> ---
> Per Larsen (1):
>       KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in host handler
> 
> Sebastian Ene (1):
>       KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler
> 
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 39 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 38 insertions(+), 1 deletion(-)
> ---
> base-commit: 6c790212c588fddeb0d852f2790840753bb604b1
> change-id: 20251029-host-direct-messages-5201d7f55abd
> 
> Best regards,
> -- 
> Per Larsen <perlarsen@google.com>
> 
> 

-- 
Sincerely,
Yeoreum Yun

Re: [PATCH v5 0/2] KVM: arm64: Support FF-A direct messaging interfaces

[Per Larsen]

Hi Yeoreum,

Sorry to keep you waiting; I'm addressing v5 feedback now.

Per

On 4/30/26 2:40 PM, Yeoreum Yun wrote:
> Hi Per,
> 
> May I ask how this patch is progressing?
> 
> Thanks!
> 
>> Support FFA_MSG_SEND_DIRECT_REQ unconditionally.
>> Support FFA_MSG_SEND_DIRECT_REQ2 if hypervisor negotiated version 1.2+.
>>
>> Framework messages (FF-A control plane) are filtered out. For
>> FFA_MSG_SEND_DIRECT_REQ, we look at flags in w2. Messages using the REQ2
>> interface are always partition messages.
>>
>> The second patch was part of a previous patch set [0] but was dropped
>> since the use case was unclear. A clear use case has now appeared: use
>> TPM device with CRB over FF-A when kernel boots with pkvm [1].
>>
>> Tested by booting Android under QEMU.
>>
>> Best Regards,
>> Per
>>
>> [0]: https://lore.kernel.org/all/20250730-virtio-msg-ffa-v9-0-7f1b55c8d149@google.com/
>> [1]: https://lore.kernel.org/all/20251027191729.1704744-1-yeoreum.yun@arm.com/
>>   
>>
>> Signed-off-by: Per Larsen <perlarsen@google.com>
>> ---
>> Changes in v5:
>> - 1/2: do_ffa_direct_msg: validate that sender is HOST_FFA_ID.
>> - Link to v4: https://lore.kernel.org/r/20260109-host-direct-messages-v4-0-95da4221d186@google.com
>>
>> Changes in v4:
>> - 1/2: do_ffa_direct_msg: check that flag in w2 is zero; drop unused vm_handle parameter.
>> - 2/2: ffa_call_supported: simplify logic by reordering cases.
>> -      do_ffa_direct_msg: switch polarity of check and update comment.
>> - Link to v3: https://lore.kernel.org/r/20251119-host-direct-messages-v3-0-c74d04944b26@google.com
>>
>> Changes in v3:
>> - Filter out framework messages as suggested by Will Deacon. Update cover letter accordingly.
>> - Update trailers: Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
>> - Link to v2: https://lore.kernel.org/r/20251030-host-direct-messages-v2-0-9f27cef36730@google.com
>>
>> Changes in v2:
>> - 1/2: Drop support for FFA_ID_GET interface in host handler.
>> - Link to v1: https://lore.kernel.org/r/20251030-host-direct-messages-v1-0-463e57871c8f@google.com
>>
>> ---
>> Per Larsen (1):
>>        KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in host handler
>>
>> Sebastian Ene (1):
>>        KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler
>>
>>   arch/arm64/kvm/hyp/nvhe/ffa.c | 39 ++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 38 insertions(+), 1 deletion(-)
>> ---
>> base-commit: 6c790212c588fddeb0d852f2790840753bb604b1
>> change-id: 20251029-host-direct-messages-5201d7f55abd
>>
>> Best regards,
>> -- 
>> Per Larsen <perlarsen@google.com>
>>
>>
>