| 21 | | On the TSAR hardware platforms containing '''32-bit cores''', the physical address has 40 bits : the 8 MSB bits define the target cluster identifier '''cxy''', and the 32 LSB bits define the local physical address '''lpa'''. On these architectures, the virtual address is 32 bits, and this virtual space is too small to map all the distributed KDATA[cxy] and KHEAP[cxy] physical segments. On these architectures, ALMOS-MKH kernel runs partially in physical addressing: the kernel code is still replicated in all clusters, and uses the '''Instruction MMU''' to map the local kernel code copy in the kernel virtual space. But, for data accesses, the '''Data MMU''' is deactivated as soon as a core enters the kernel, and it is reactivated when it returns to user. ALMOS-MK uses a software controlable (TSAR-specific) register, containing a '''cxy''' value. This '''cxy''' cluster identifier is concatenated to the 32 bits '''ptr''' pointer to build (in pseudo identity mapping) a 40 bits physical address. The default value for this register is the local cluster identifier, and is used to access the local physical memory. To access physical memory in a remote cluster, the ''remote_read'' and ''remote_write'' primitives modify the extension register before the remote memory access, and restore it after the remote memory access. |
| | 21 | On the TSAR hardware platforms containing '''32-bit cores''', the physical address has 40 bits : the 8 MSB bits define the target cluster identifier '''cxy''', and the 32 LSB bits define the local physical address '''lpa'''. On these architectures, the virtual address is 32 bits, and this virtual space is too small to map all the distributed KDATA[cxy] and KHEAP[cxy] physical segments. On these architectures, ALMOS-MKH kernel runs partially in physical addressing: the kernel code is still replicated in all clusters, and uses the '''Instruction MMU''' to map the local kernel code copy in the kernel virtual space. But, for data accesses, the '''Data MMU''' is deactivated as soon as a core enters the kernel, and it is reactivated when it returns to user. ALMOS-MK uses a software controlable (TSAR-specific) extension register, containing a '''cxy''' value. When the Data MMU is deactivated, this '''cxy''' cluster identifier is concatenated to the 32 bits '''ptr''' pointer to build (in pseudo identity mapping) a 40 bits physical address. The default value for this extension register is the local cluster identifier, and is used to access the local memory. To access memory in a remote cluster, the ''remote_read'' and ''remote_write'' primitives modify the extension register before the remote memory access, and restore it after the remote memory access. |
