linux-kernel - [RESEND PATCH V3 0/2] riscv: add RISC-V Svpbmt Standard Extension supports

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Date:   Mon, 25 Oct 2021 12:06:05 +0800
From:   wefu@...hat.com
To:     anup.patel@....com, atish.patra@....com, palmerdabbelt@...gle.com,
        guoren@...nel.org, christoph.muellner@...ll.eu,
        philipp.tomsich@...ll.eu, hch@....de, liush@...winnertech.com,
        wefu@...hat.com, lazyparser@...il.com, drew@...gleboard.org
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        taiten.peng@...onical.com, aniket.ponkshe@...onical.com,
        heinrich.schuchardt@...onical.com, gordan.markus@...onical.com,
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Subject: [RESEND PATCH V3 0/2] riscv: add RISC-V Svpbmt Standard Extension supports

From: Fu Wei <wefu@...hat.com>

This patch follows the  RISC-V standard Svpbmt extension in 
privilege spec to solve the non-coherent SOC DMA synchronization
issues.

The svpbmt PTE format:
| 63 | 62-61 | 60-8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
  N     MT     RSW    D   A   G   U   X   W   R   V
        ^

Of the Reserved bits [63:54] in a leaf PTE, the bits [62:61] are used as
the MT (aka MemType) field. This field specifies one of three memory types
as shown in the following table：
MemType     RISC-V Description
----------  ------------------------------------------------
00 - PMA    Normal Cacheable, No change to implied PMA memory type
01 - NC     Non-cacheable, idempotent, weakly-ordered Main Memory
10 - IO     Non-cacheable, non-idempotent, strongly-ordered I/O memory
11 - Rsvd   Reserved for future standard use

The standard protection_map[] needn't be modified because the "PMA"
type keeps the highest bits zero.
And the whole modification is limited in the arch/riscv/* and using
a global variable(__riscv_svpbmt) as _PAGE_DMA_MASK/IO/NC for
pgprot_noncached (&writecombine) in pgtable.h.
We also add _PAGE_CHG_MASK to filter PFN than before.

Enable it in devicetree - (Add "mmu-supports-svpbmt" in cpu node)
 - mmu-supports-svpbmt

Wei Fu (2):
  dt-bindings: riscv: add mmu-supports-svpbmt for Svpbmt
  riscv: add RISC-V Svpbmt extension supports

 .../devicetree/bindings/riscv/cpus.yaml       |  5 +++
 arch/riscv/include/asm/fixmap.h               |  2 +-
 arch/riscv/include/asm/pgtable-64.h           |  8 ++--
 arch/riscv/include/asm/pgtable-bits.h         | 41 ++++++++++++++++++-
 arch/riscv/include/asm/pgtable.h              | 39 ++++++++++++++----
 arch/riscv/kernel/cpufeature.c                | 32 +++++++++++++++
 arch/riscv/mm/init.c                          |  5 +++
 7 files changed, 117 insertions(+), 15 deletions(-)

-- 
2.25.4