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From: Paul Mackerras <paulus@samba.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH -V5 13/13] arch/powerpc: Update VSID allocation documentation
Date: Wed, 1 Aug 2012 15:35:05 +1000	[thread overview]
Message-ID: <20120801053505.GG24014@drongo> (raw)
In-Reply-To: <1343647339-25576-14-git-send-email-aneesh.kumar@linux.vnet.ibm.com>

On Mon, Jul 30, 2012 at 04:52:19PM +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@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.

  reply	other threads:[~2012-08-01  5:35 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-30 11:22 [PATCH -V5 0/13] arch/powerpc: Add 64TB support to ppc64 Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 01/13] arch/powerpc: Use hpt_va to compute virtual address Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 02/13] arch/powerpc: Simplify hpte_decode Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 03/13] arch/powerpc: Convert virtual address to vpn Aneesh Kumar K.V
2012-08-01  4:33   ` Paul Mackerras
2012-08-01  7:23     ` Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 04/13] arch/powerpc: Rename va " Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 05/13] arch/powerpc: Make KERN_VIRT_SIZE not dependend on PGTABLE_RANGE Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 06/13] arch/powerpc: Increase the slice range to 64TB Aneesh Kumar K.V
2012-08-01  5:16   ` Paul Mackerras
2012-08-01  7:43     ` Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 07/13] arch/powerpc: Make some of the PGTABLE_RANGE dependency explicit Aneesh Kumar K.V
2012-08-01  5:18   ` Paul Mackerras
2012-08-01  7:45     ` Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 08/13] arch/powerpc: Use the rquired number of VSID bits in slbmte Aneesh Kumar K.V
2012-08-01  5:19   ` Paul Mackerras
2012-07-30 11:22 ` [PATCH -V5 09/13] arch/powerpc: Use 32bit array for slb cache Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 10/13] arch/powerpc: Add 64TB support Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 11/13] arch/powerpc: properly isolate kernel and user proto-VSID Aneesh Kumar K.V
2012-08-01  4:31   ` Paul Mackerras
2012-08-01  7:58     ` Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 12/13] arch/powerpc: Replace open coded CONTEXT_BITS value Aneesh Kumar K.V
2012-08-01  5:29   ` Paul Mackerras
2012-08-01  9:56     ` Aneesh Kumar K.V
2012-07-30 11:22 ` [PATCH -V5 13/13] arch/powerpc: Update VSID allocation documentation Aneesh Kumar K.V
2012-08-01  5:35   ` Paul Mackerras [this message]
2012-08-01 10:01     ` Aneesh Kumar K.V

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