Jan Kiszka <[email protected]> 于2021年9月10日周五 下午6:29写道： > > On 07.09.21 15:39, Dongjiu Geng wrote: > > Hi, > > sorry to disturb you, I have a question to consult with you, > > why does Jailhouse not call paging_destroy() to unmap the address when > > it finishes accessing the physical address? as shown in [1] that > > handing mmio subpage access. > > I think it is better to unmap the address after finishing MMIO access. > > > > [1]: > > static enum mmio_result mmio_handle_subpage(void *arg, struct mmio_access > > *mmio) > > { > > ........ > > err = paging_create(&this_cpu_data()->pg_structs, page_phys, > > PAGE_SIZE, > > TEMPORARY_MAPPING_BASE, > > PAGE_DEFAULT_FLAGS | PAGE_FLAG_DEVICE, > > PAGING_NON_COHERENT | PAGING_NO_HUGE); > > if (err) > > goto invalid_access; > > .................... > > return MMIO_HANDLED; > > > > invalid_access: > > panic_printk("FATAL: Invalid MMIO %s, address: %lx, size: %x\n", > > mmio->is_write ? "write" : "read", > > (unsigned long)mem->phys_start + mmio->address, > > mmio->size); > > return MMIO_ERROR; > > } > > > > We never unmap those CPU-local temporary mappings, we only overwrite > them as needed. Theoretically, we could invalidate the mapping after > use, but that would also require related TLB invalidation and would add > to the overhead. Without a significant gain on robustness, this step is > not really desirable. It's always a trade-off...
Understand it now, thanks very much for your explaination and reply. > > Jan > > -- > Siemens AG, T RDA IOT > Corporate Competence Center Embedded Linux -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/CABSBigTG0Z5daX_gsGmUUYorpaFB8Q3x-rVuTOpaEhOSv-JryA%40mail.gmail.com.
