Sorry for my mistake. I misunderstood some functions in nvs.c. So I have fixed it and sent my email again. My email is below. > > > Matthew pointed out that having a hook in NVS driver is better solution > > > because it is nil functionality if the TPM driver is loaded. We need > > > functions to: > > > > > > 1. Request a region from the NVS driver (when tpm_crb loads) > > > 2. Release a region back to the NVS Driver (when tpm_crb unloads). > > > > > > My proposal would unnecessarily duplicate code and also leave a > > > side-effect when TPM is not used in the first place. > > > > > > I see this as the overally best solution. If you can come up with a > > > patch for the NVS side and changes to CRB drivers to utilize the new > > > hooks, then combined with Vanya's changes we have a sustainable solution > > > for AMD fTPM. > > > > It's a great solution. I will update this patch on your advice and > > send it to you soon. > > > > By the way, I have a question about your advice. > > If we handle the NVS region with NVS driver, calling devm_ioremap() > > function is fine like crb_ioremap_resource() function in this patch? > > No, you should reclaim the resource that conflicts and return it back > when tpm_crb is unregistered (e.g. rmmod tpm_crb). > > I would try something like enumerating iomem resources with > walk_iomem_res_desc(). I would advice to peek at arch/x86/kernel/crash.c > for an example how to use this for NVS regions > > Then you could __release_region() to unallocate the source. When tpm_crb > is removed you can then allocate and insert a resource with data > matching it had. Thank you for your sincere advice, and I have some questions about it. As you know, the core reason of this ACPI NVS problem is that a busy bit is set to the ACPI NVS area. So, devm_ioremap_resource() function fails because of it. If we want to call devm_ioremap_resource() for this case, we maybe need to rearrange the existing memory layout from the child relationship to the sibling relationship below. We also need to get back when tpm_crb unloads. [ ACPI NVS (parent) [ TPM CMD buffer (child of NVS) ] [ TPM RSP buffer (child of NVS) ] ] <---> [ ACPI NVS head ] [ CMD buffer ] [ NVS middle ] [ RSP buffer ] [ NVS tails ] Our concern is a race condition between NVS driver and TPM CRB driver. In my view, we could solve this problem if we only make and call the functions you said, requesting and releasing a region from NVS driver. NVS driver doesn't rely on iomem layout, and it relies on internal nvs_region_list data. Therefore, I added some details to your guide. How about this sequence? 1) When tpm_crb driver loads, the driver checks if command/response buffers are in ACPI NVS area. If so, it requests (or removes) the buffer regions from NVS driver's nvs_region_list (with acpi_nvs_unregister() function I will add to the nvs.c driver). 2) If command/response buffers are in ACPI NVS area, tpm_crb driver calls devm_ioremap() instead of devm_ioremap_resource() like this patch. 3) When tpm_crb driver unloads, the driver releases (or adds) the buffer regions to NVS driver's nvs_region_list (with existing acpi_nvs_register() function in the nvs.c driver). I think the sequence could solve the problem we concerned. What do you think about the sequence? Seunghun
