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. 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 ? Cheers Bertrand
