On Sun, Sep 29, 2019 at 11:28:43PM -0600, Stephen Warren wrote: > On 9/29/19 2:08 PM, Mian Yousaf Kaukab wrote: > > Most of the SysRAM is secure and only accessible by TF-A. > > Don't map this inaccessible memory in kernel. Only map pages > > used by bpmp driver. > > I don't believe this change is correct. The actual patch doesn't > implement mapping a subset of the RAM (a software issue), but rather it > changes the DT representation of the SYSRAM hardware. The SYSRAM > hardware always does start at 0x30000000, even if a subset of the > address range is dedicated to a specific purpose. If the kernel must map > only part of the RAM, then some additional property should indicate > this.[...] I agree the hardware description becomes inaccurate with this change.
In the current setup complete 0x3000_0000 to 0x3005_0000 range is being mapped as normal memory (MT_NORMAL_NC). Though only 0x3004_E000 to 0x3005_0000 are accessible by the kernel. I am seeing an issue where a read access (which I believe is speculative) to inaccessible range causes an SError. Another solution for this problem could be to add "no-memory-wc" to SysRAM node so that it is mapped as device memory (MT_DEVICE_nGnRE). Would that be acceptable? > [...] Also, I believe it's incorrect to hard-code into the kernel's DT > the range of addresses used by the secure monitor/OS, since this can > vary depending on what the user actually chooses to install as the > secure monitor/OS. Any indication of such regions should be filled in at > runtime by some boot firmware or the secure monitor/OS itself, or > retrieved using some runtime API rather than DT. Secure-OS addresses are not of interest here. SysRAM is partitioned between secure-OS and BPMP and kernel is only interested in the BPMP part. The firmware can update these addresses in the device-tree if it wants to. Would you prefer something similar implemented in u-boot so that it updates SysRAM node to only expose kernel accessible part of it to the kernel? Can u-boot dynamically figure out the Secure-OS vs BPMP partition? BR, Yousaf
