Hi Bertrand, On Wed, Feb 11, 2026 at 12:27 PM Bertrand Marquis <[email protected]> wrote: > > Hi Jens, > > > On 11 Feb 2026, at 09:17, Jens Wiklander <[email protected]> wrote: > > > > Hi Bertrand, > > > > On Tue, Feb 3, 2026 at 6:38 PM Bertrand Marquis > > <[email protected]> wrote: > >> > >> FFA_FEATURES currently accepts non-zero input properties (w2-w7) from > >> guests and advertises several ABIs unconditionally, even when firmware > >> support is missing or when the ABI is physical-instance-only. This can > >> mislead guests about what Xen can actually provide and violates FF-A > >> calling conventions. Some SPMCs (Hafnium v2.14 or earlier) also fail to > >> report FFA_RX_ACQUIRE despite supporting it. > >> > >> Update FFA_FEATURES validation to match spec and firmware support: > >> - reject non-zero w2-w7 input properties with INVALID_PARAMETERS > >> - reject 64-bit calling conventions from 32-bit guests with NOT_SUPPORTED > >> - return NOT_SUPPORTED for physical-instance-only ABIs > >> (FFA_NOTIFICATION_BITMAP_{CREATE,DESTROY}, FFA_RX_ACQUIRE) > >> - advertise FFA_INTERRUPT as supported > >> - gate message ABIs on firmware support: > >> - FFA_MSG_SEND_DIRECT_REQ_{32,64} > >> - FFA_MSG_SEND_DIRECT_REQ2 (also requires FF-A 1.2 negotiation) > >> - FFA_MSG_SEND2 (or VM-to-VM enabled) > >> - report MEM_SHARE_{32,64} only when FFA_MEM_SHARE_64 is supported > >> - stop advertising FFA_MSG_YIELD (not implemented) > >> > >> Update firmware probing: drop FFA_MEM_SHARE_32 checks (deprecated) and > >> add FFA_RX_ACQUIRE to the probed set. If FFA_MSG_SEND2 is reported but > >> FFA_RX_ACQUIRE is not, assume RX_ACQUIRE support and warn to work > >> around the Hafnium bug. > >> > >> Functional impact: guests now see ABI support that reflects firmware > >> capabilities and Xen implementation status. When SEND2 is present but > >> RX_ACQUIRE is not reported, Xen assumes RX_ACQUIRE support. > >> > >> Signed-off-by: Bertrand Marquis <[email protected]> > >> --- > >> xen/arch/arm/tee/ffa.c | 62 +++++++++++++++++++++++++++++++++++++----- > >> 1 file changed, 55 insertions(+), 7 deletions(-) > >> > >> diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c > >> index 6de2b9f8ac8e..e9e020bb0cb3 100644 > >> --- a/xen/arch/arm/tee/ffa.c > >> +++ b/xen/arch/arm/tee/ffa.c > >> @@ -91,10 +91,10 @@ static const struct ffa_fw_abi ffa_fw_abi_needed[] = { > >> FW_ABI(FFA_PARTITION_INFO_GET), > >> FW_ABI(FFA_NOTIFICATION_INFO_GET_64), > >> FW_ABI(FFA_NOTIFICATION_GET), > >> + FW_ABI(FFA_RX_ACQUIRE), > >> FW_ABI(FFA_RX_RELEASE), > >> FW_ABI(FFA_RXTX_MAP_64), > >> FW_ABI(FFA_RXTX_UNMAP), > >> - FW_ABI(FFA_MEM_SHARE_32), > >> FW_ABI(FFA_MEM_SHARE_64), > >> FW_ABI(FFA_MEM_RECLAIM), > >> FW_ABI(FFA_MSG_SEND_DIRECT_REQ_32), > >> @@ -240,19 +240,39 @@ static void handle_features(struct cpu_user_regs > >> *regs) > >> struct ffa_ctx *ctx = d->arch.tee; > >> unsigned int n; > >> > >> + /* > >> + * Xen does not accept any non-zero FFA_FEATURES input properties from > >> + * VMs. The spec only defines w2 input properties for > >> FFA_MEM_RETRIEVE_REQ > >> + * (NS-bit negotiation for SP/SPMC) and FFA_RXTX_MAP (buffer size and > >> + * alignment), so w2 must be MBZ for our callers. > >> + */ > > > > The spec (version 1.2) lists them as SBZ, except for w2, which is MBZ, > > for Feature IDs. > > Very true, this should only check w2 which is anyway defined as MBZ when > not used. > w3-w7 were MBZ in previous versions of FF-A but are in fact SBZ in 1.2 so > we should ignore them > > > However, if we're to return an error, invalid parameters is a better choice. > > In fact the spec is actually saying the following: > If the FF-A interface or feature that was queried is not implemented or > invalid, > the callee completes this call with an invocation of the FFA_ERROR interface > with the NOT_SUPPORTED error code. > > So there is no case for INVALID_PARAMETER.
You're right. > > So in fact i should: > - return NOT_SUPPORTED if w2 is not 0 > - ignore w3-w7 > > Can you confirm that you have the same reading of the spec than me ? The 1.2 spec only says this w2 is MBZ for Feature IDs, and that w2 is SBZ for FFA_RXTX_MAP. The 1.3 spec says the same, except that in Table 13.14: Feature IDs and properties table, it lists w2 as SBZ. Note that FFA_MEM_RETRIEVE_REQ has bits defined in w2, and the unknown bits are SBZ. Based on that, I'm inclined to keep it simple and ignore w2-w7. Cheers, Jens
