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charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260505_041702_972185_9A5499B7 X-CRM114-Status: GOOD ( 32.80 ) 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 Ben, > > > Hi Levi, > > > > On 5/5/26 10:54, Yeoreum Yun wrote: > > > This patch is split out from the patchset [0] -- > > > fix FF-A call failure with pKVM when the FF-A driver is built-in, > > > specifically the IMA-related part. > > > > > > 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. > > > > > > This patch is based on v7.1-rc2 > > > > > > Question: > > > > > > FF-A initialisation can occur at late_initcall. Because it may be deferred, > > > some FF-A requests cannot be serviced at that stage. > > > A typical example is the EFI runtime variable service using DIRECT_MSG_REQ. > > > > > > Depending on the platform, the EFI runtime variable service runs with StandaloneMm > > > and uses FF-A DIRECT_REQ. However, when pKVM is enabled, FF-A initialisation > > > may be deferred to late_initcall. In this case, load_uefi_certs() > > > can fail if it is invoked before the FF-A driver is initialised > > > via deferred_probe_initcall(). > > > > > > Moving load_uefi_certs() to late_initcall_sync, as in the third patch, > > > seems not to have any problem since late_initcall and > > > late_initcall_sync are both of do_basic_setup() and it's before loading > > > init process. However, it is still unclear whether > > > it would be better to allow DIRECT_MSG_REQ in kvm_host_ffa_handler() > > > > The spec doesn't allow this. Looking at DEN0077A 1.2 REL0: > > > > Section 13.2.2 says: > > > > "If they are compatible, it enables them to determine which Framework functionalities can be used. Hence, negotiation of > > the version must happen before an invocation of any other FF-A ABI." > > > > and a bit further down > > > > "Once the caller invokes any FF-A ABI other than FFA_VERSION, the version negotiation phase is complete." > > > > I would have thought that an SP would only go into the waiting state once the version negotiation is done. > > I mean the negotiation between hypervisor and ff-a driver. > actually the version negotiation is done with SPMC in > hyp_ffa_init() but the negotiaion between hypervisor and ff-a driver > just choose the lower version between version requested from ff-a driver > and negotiated version with hypervisor and SPMC. Sorry. re-parse the word, not choose "re-negotiate" when FF-A driver request lowever version. > > So, the version negotiation is already done with SPMC > but with FF-A driver with hypervisor is not yet. > However, DIRECT_MSG_REQ has supported from v1.0 > In this situation, is there any reason not to send DIRECT_REQ_MSG? IOW, question is that some of ff-a request can be allowed before version negotiation with FF-A driver but using negotiated version via hyp_ffa_init() first or not. [...] Thanks. -- Sincerely, Yeoreum Yun