On Wed, 2011-10-05 at 18:19 +0530, Suzuki Poulose wrote: > #define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) - > PHYSICAL_START + KERNELBASE) > > where, > PHYSICAL_START is #define'd to kernstart_addr variable, updated at > boot
Where kernstart_addr is the physical address of where we loaded the kernel. But, this has the side-effect of also shifting the kernel's identity mapping (the 1:1 virtual-to-physical map) up by that amount. I'm unconvinced that this movement of the identity mapping is necessary. Even if it is, Suzuki mentions: > #define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) - > PHYSICAL_START + KERNELBASE) > where: > PHYSICAL_START is kernstart_addr - a variable updated at runtime. > KERNELBASE is the compile time Virtual base address of kernel. > > This won't work for us, as the kernstart_addr may change at runtime, even > though the mapping doesn't change. That seems to tell me that PHYSICAL_START and kernstart_addr shouldn't be the same variable. We should break them apart so that we can move the kernel's starting physical address without changing the virt/phys mapping. Which, I'm fearing, was what Suzuki's first patch did, and I failed to grok it. -- Dave _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
