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charset=us-ascii Content-Disposition: inline In-Reply-To: <20260505-super-gecko-of-argument-655030@sudeepholla> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260505_080659_658028_B1C254BB X-CRM114-Status: GOOD ( 20.98 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Sudeep, > On Tue, May 05, 2026 at 10:54:08AM +0100, Yeoreum Yun wrote: > > When pKVM is enabled, the FF-A driver must be initialised after pKVM. > > Otherwise, pKVM cannot negotiate the FF-A version or obtain the RX/TX > > buffer information, leading to failures in FF-A calls. > > > > Currently, pKVM initialisation completes at device_initcall_sync, > > while ffa_init() runs at the device_initcall level. > > > > So far, linker deployes kvm_arm_init() before ffa_init(), and SMCs can > > still be trapped even before finalise_pkvm() is invoked. > > As a result, this issue has not been observed. > > > > However, relying on above stuff is fragile. > > Therefore, when pKVM is enabled, the FF-A infrastructure should be > > initialised only after pKVM initialisation has been fully finalised. > > > > To achieve this, introduce an ffa_root_dev ("arm-ffa") and > > a corresponding driver to defer initialisation of the FF-A infrastructure > > until pKVM initialisation is complete, and to defer probing of all FF-A devices until then > > when pKVM is enabled. > > > > I don't like this whole ffa root device design. > Two question for now: > 1. Can FF-A be a module on systems with pKVM which removes the need for all > this dance done here ? But this means we reduce the other feature e.x) IMA with TPM over FF-A and pKVM feature. Since IMA must be a built-in, we couldn't avoid to build FF-A driver with built-in. > 2. If it is a requirement to have this built-in, I prefer to add a probe > and defer it instead of this root ffa device. But, How? anyway all of FF-A device & driver couldn't be probed unless FF-A initialisation is finished and How can we trigger FF-A initailise after pKVM finish its initialisation? The problem is ff-a intiailisation happens before pKVM finish its initailasation and to do defer probe, it should use dd-model and As we discussed in other thread, notifier couldn't be a soluation. Could you let me share other way I'm missing? Thanks! > -- > Regards, > Sudeep -- Sincerely, Yeoreum Yun