On Mon, Jul 30, 2012 at 04:52:19PM +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com>
>
> This update the proto-VSID and VSID scramble related information
> to be more generic by using names instead of current values.
Comments below...
> - * VSID allocation
> + * VSID allocation (256MB segment)
> *
> - * We first generate a 36-bit "proto-VSID". For kernel addresses this
> - * is equal to the ESID, for user addresses it is:
> - * (context << 15) | (esid & 0x7fff)
> + * We first generate a 38-bit "proto-VSID". For kernel addresses this
> + * is equal to the ESID | 1 << 37, for user addresses it is:
> + * (context << USER_ESID_BITS) | (esid & (1U << USER_ESID_BITS))
^^^^^^^^^^^^^^^^^^^^^^
should be ((1U << USER_ESID_BITS) - 1)
> *
> - * The two forms are distinguishable because the top bit is 0 for user
> - * addresses, whereas the top two bits are 1 for kernel addresses.
> - * Proto-VSIDs with the top two bits equal to 0b10 are reserved for
> - * now.
> + * This splits the proto-VSID into the below range
> + * 0 - (2^(CONTEXT_BITS + USER_ESID_BITS) - 1) : User proto-VSID range
> + * 2^(CONTEXT_BITS + USER_ESID_BITS) - 2^(VSID_BITS) : Kernel proto-VSID
> range
Perhaps point out also that CONTEXT_BITS + USER_ESID_BITS == VSID_BITS - 1,
that is, you have assigned half of the space to user processes and half
to the kernel.
> -/*
> - * WARNING - If you change these you must make sure the asm
> - * implementations in slb_allocate (slb_low.S), do_stab_bolted
> - * (head.S) and ASM_VSID_SCRAMBLE (below) are changed accordingly.
> - */
Are you absolutely sure that nothing in the assembly code would need
to be changed if someone changed these definitions?
Paul.
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