From: "Clément Léger" <cleger@rivosinc.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: "Clément Léger" <cleger@rivosinc.com>,
"Conor Dooley" <conor.dooley@microchip.com>,
"Andrew Jones" <ajones@ventanamicro.com>,
"Damien Le Moal" <dlemoal@kernel.org>,
"Björn Töpel" <bjorn@rivosinc.com>,
"Atish Patra" <atishp@rivosinc.com>
Subject: [PATCH] riscv: deprecate CONFIG_MMU=n
Date: Mon, 26 Feb 2024 15:06:46 +0100 [thread overview]
Message-ID: <20240226140649.293254-1-cleger@rivosinc.com> (raw)
Deprecation of NOMMU support for riscv was discussed during LPC 2023
[1]. Reasons for this involves lack of users as well as maintenance
efforts to support this mode. psABI FDPIC specification also never
made it upstream and last public messages of this development seems to
date back from 2020 [2]. Plan the deprecation to be done in 2 years from
now. Mark the Kconfig option as deprecated by adding a new dummy option
which explicitly displays the deprecation in case of CONFIG_MMU=n. This option
is selected indirectly by CONFIG_RISCV_M_MODE since an option can not
select another one directly with a "select" in case of such CONFIG=n.
Additionally, display a pr_err() message at boot time in case of NOMMU
build to warn about upcoming deprecation.
Link: https://lpc.events/event/17/contributions/1478/ [1]
Link: https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/ZjYUJswknQ4/m/WYRRylTwAAAJ [2]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
arch/riscv/Kconfig | 8 ++++++++
arch/riscv/kernel/setup.c | 4 ++++
2 files changed, 12 insertions(+)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index bffbd869a068..8da58c102d3f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -221,6 +221,7 @@ config ARCH_MMAP_RND_COMPAT_BITS_MAX
# set if we run in machine mode, cleared if we run in supervisor mode
config RISCV_M_MODE
bool
+ select NOMMU
default !MMU
# set if we are running in S-mode and can use SBI calls
@@ -236,6 +237,13 @@ config MMU
Select if you want MMU-based virtualised addressing space
support by paged memory management. If unsure, say 'Y'.
+config NOMMU
+ depends on !MMU
+ bool "NOMMU kernel (DEPRECATED)"
+ help
+ NOMMU kernel is deprecated and is scheduled for removal by
+ the beginning of 2027.
+
config PAGE_OFFSET
hex
default 0xC0000000 if 32BIT && MMU
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 4f73c0ae44b2..8799816ef0a6 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -295,6 +295,10 @@ void __init setup_arch(char **cmdline_p)
riscv_set_dma_cache_alignment();
riscv_user_isa_enable();
+
+#if !defined(CONFIG_MMU)
+ pr_err("RISC-V NOMMU support is deprecated and scheduled for removal by the beginning of 2027\n");
+#endif
}
bool arch_cpu_is_hotpluggable(int cpu)
--
2.43.0
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next reply other threads:[~2024-02-26 14:08 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 14:06 Clément Léger [this message]
2024-02-26 14:57 ` [PATCH] riscv: deprecate CONFIG_MMU=n Damien Le Moal
2024-02-26 14:59 ` Clément Léger
2024-02-26 15:01 ` Damien Le Moal
2024-02-26 15:14 ` Samuel Holland
2024-02-26 15:25 ` Clément Léger
2024-02-26 16:02 ` Conor Dooley
2024-02-26 19:00 ` Charles Lohr
2024-02-26 21:29 ` Conor Dooley
2024-02-27 9:11 ` Clément Léger
2024-02-27 16:38 ` Palmer Dabbelt
2024-03-14 12:46 ` Jisheng Zhang
2024-03-14 13:02 ` Jisheng Zhang
2024-03-25 16:59 ` Jisheng Zhang
2024-03-26 20:25 ` Charles Lohr
2024-03-27 1:14 ` Jisheng Zhang
2024-03-27 1:34 ` Charles Lohr
2024-03-27 3:40 ` Jisheng Zhang
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