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From: Nick Kossifidis <mick@ics.forth.gr>
To: guoren@kernel.org
Cc: anup.patel@wdc.com, palmerdabbelt@google.com, arnd@arndb.de,
	wens@csie.org, maxime@cerno.tech, drew@beagleboard.org,
	liush@allwinnertech.com, lazyparser@gmail.com, wefu@redhat.com,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-sunxi@lists.linux.dev,
	Guo Ren <guoren@linux.alibaba.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC PATCH v2 06/11] riscv: pgtable: Add DMA_COHERENT with custom PTE attributes
Date: Sun, 06 Jun 2021 20:22:14 +0300	[thread overview]
Message-ID: <610849b6f66e8d5a9653c9f62f46c48d@mailhost.ics.forth.gr> (raw)
In-Reply-To: <1622970249-50770-10-git-send-email-guoren@kernel.org>

Στις 2021-06-06 12:04, guoren@kernel.org έγραψε:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> The dma-noncoherent SOCs need different virtual memory mappings
> with different attributes:
>  - noncached + Strong Order (for IO/DMA descriptor)
>  - noncached + Weak Order (for writecombine usage, eg: frame
>    buffer)
> 
> All above base on PTE attributes by MMU hardware. That means
> address attributes are determined by PTE entry, not PMA. RISC-V
> soc vendors have defined their own custom PTE attributes for
> dma-noncoherency.
> 

This patch violates the Privilege Spec section 4.4.1 that clearly 
states:

"Bits63–54 are reserved for future standard use and must be zeroed by 
software for forward compatibility"

Standard use means that valid values can only be defined by the Priv. 
Spec, not by the vendor (otherwise they'd be marked as "custom use" or 
"platform use"), and since they "must" be zeroed by software we 'll be 
violating the Privilege Spec if we do otherwise.

  parent reply	other threads:[~2021-06-06 17:47 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-06  9:03 [RFC PATCH v2 00/11] riscv: Add DMA_COHERENT support for Allwinner D1 guoren
2021-06-06  9:03 ` [RFC PATCH v2 01/11] riscv: asid: Use global mappings for kernel pages guoren
2021-06-06  9:03 ` [PATCH V5 1/3] riscv: " guoren
2021-06-06  9:03 ` [PATCH V5 2/3] riscv: Add ASID-based tlbflushing methods guoren
2021-06-06 14:38   ` Christoph Hellwig
2021-06-06  9:03 ` [RFC PATCH v2 02/11] riscv: asid: " guoren
2021-06-06  9:04 ` [RFC PATCH v2 03/11] riscv: asid: Optimize tlbflush coding convention guoren
2021-06-06  9:04 ` [PATCH V5 3/3] riscv: tlbflush: Optimize " guoren
2021-06-06  9:04 ` [RFC PATCH v2 04/11] riscv: pgtable: Fixup _PAGE_CHG_MASK usage guoren
2021-06-06  9:04 ` [RFC PATCH v2 05/11] riscv: pgtable: Add custom protection_map init guoren
2021-06-06  9:04 ` [RFC PATCH v2 06/11] riscv: pgtable: Add DMA_COHERENT with custom PTE attributes guoren
2021-06-06 14:39   ` Christoph Hellwig
2021-06-06 15:08     ` Guo Ren
2021-06-06 17:22   ` Nick Kossifidis [this message]
2021-06-07  6:19     ` Christoph Hellwig
2021-06-06  9:04 ` [RFC PATCH v2 07/11] riscv: cmo: Add dma-noncoherency support guoren
2021-06-06  9:04 ` [RFC PATCH v2 08/11] riscv: cmo: Add vendor custom icache sync guoren
2021-06-06  9:04 ` [RFC PATCH v2 09/11] riscv: soc: Initial DTS for Allwinner D1 NeZha board guoren
2021-06-06 16:26   ` Jernej Škrabec
2021-06-06 17:05     ` Guo Ren
2021-06-07  3:44     ` Guo Ren
2021-06-07  7:27       ` Maxime Ripard
2021-06-07  7:53         ` Guo Ren
2021-06-07  7:24   ` Maxime Ripard
2021-06-07  8:07     ` Guo Ren
2021-06-14 15:33       ` Maxime Ripard
2021-06-14 16:28         ` Guo Ren
2021-06-14 16:31           ` Jernej Škrabec
2021-06-06  9:04 ` [RFC PATCH v2 10/11] riscv: soc: Add Allwinner SoC kconfig option guoren
2021-06-07  7:19   ` Maxime Ripard
2021-06-07  7:27     ` Arnd Bergmann
2021-06-07  7:45       ` Guo Ren
2021-06-07  7:43     ` Guo Ren
2021-06-07 12:12       ` Maxime Ripard
2021-06-07 12:39         ` Guo Ren
2021-06-06  9:04 ` [RFC PATCH v2 11/11] riscv: soc: Allwinner D1 GMAC driver only for temp use guoren
2021-06-06 10:50   ` Andre Przywara
2021-06-06 15:32     ` Guo Ren
2021-06-06 15:39       ` Jernej Škrabec
2021-06-06 15:41         ` Guo Ren
2021-06-06 16:16   ` Arnd Bergmann
2021-06-06 16:32     ` Jernej Škrabec
2021-06-06 16:53       ` Guo Ren
2021-06-06 16:53     ` Guo Ren
2021-06-06 16:29 ` [RFC PATCH v2 00/11] riscv: Add DMA_COHERENT support for Allwinner D1 Jernej Škrabec
2021-06-06 16:54   ` Guo Ren
2021-06-06 17:14     ` Jernej Škrabec
2021-06-06 23:42       ` Guo Ren
2021-06-07  3:44 ` Anup Patel
2021-06-07  4:36   ` Guo Ren

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