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Date: Mon, 06 May 2024 18:40:44 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Conor Dooley <conor.dooley@...rochip.com>, Song Liu <song@...nel.org>,
Xi Wang <xi.wang@...il.com>,
Björn Töpel <bjorn@...osinc.com>,
Clément Léger <cleger@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 3/8] riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_SVNAPOT Kconfig
option
The previously supported config RISCV_ISA_SVNAPOT has been renamed to
PLATFORM_MAY_SUPPORT_RISCV_ISA_SVNAPOT and the config
PLATFORM_SUPPORTS_RISCV_ISA_SVNAPOT has been introduced to compile a
kernel that will use svnapot by default. Both of these configs select a
hidden CONFIG_RISCV_ISA_SVNAPOT that can be used to determin if SVNAPOT
is allowed to be used.
Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
arch/riscv/Kconfig | 21 +------------------
arch/riscv/Kconfig.isa | 44 ++++++++++++++++++++++++++++++++++++++++
arch/riscv/include/asm/pgtable.h | 3 ++-
3 files changed, 47 insertions(+), 21 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c2e9eded0a7d..9c3a4347953b 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -63,7 +63,7 @@ config RISCV
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if SMP && MMU
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_FRAME_POINTERS
- select ARCH_WANT_GENERAL_HUGETLB if !RISCV_ISA_SVNAPOT
+ select ARCH_WANT_GENERAL_HUGETLB if !PLATFORM_MAY_SUPPORT_RISCV_ISA_SVNAPOT
select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
select ARCH_WANT_LD_ORPHAN_WARN if !XIP_KERNEL
select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
@@ -484,25 +484,6 @@ config RISCV_ALTERNATIVE_EARLY
help
Allows early patching of the kernel for special errata
-config RISCV_ISA_SVNAPOT
- bool "Svnapot extension support for supervisor mode NAPOT pages"
- depends on 64BIT && MMU
- depends on RISCV_ALTERNATIVE
- default y
- help
- Add support for the Svnapot ISA-extension in the kernel when it
- is detected at boot.
-
- The Svnapot extension is used to mark contiguous PTEs as a range
- of contiguous virtual-to-physical translations for a naturally
- aligned power-of-2 (NAPOT) granularity larger than the base 4KB page
- size. When HUGETLBFS is also selected this option unconditionally
- allocates some memory for each NAPOT page size supported by the kernel.
- When optimizing for low memory consumption and for platforms without
- the Svnapot extension, it may be better to say N here.
-
- If you don't know what to do here, say Y.
-
config RISCV_ISA_SVPBMT
bool "Svpbmt extension support for supervisor mode page-based memory types"
depends on 64BIT && MMU
diff --git a/arch/riscv/Kconfig.isa b/arch/riscv/Kconfig.isa
index 0663c98b5b17..37585bcd763e 100644
--- a/arch/riscv/Kconfig.isa
+++ b/arch/riscv/Kconfig.isa
@@ -124,3 +124,47 @@ config RISCV_ISA_V_PREEMPTIVE
This config allows kernel to run SIMD without explicitly disable
preemption. Enabling this config will result in higher memory
consumption due to the allocation of per-task's kernel Vector context.
+
+config RISCV_ISA_SVNAPOT
+ bool
+
+choice
+ prompt "Svnapot extension support for supervisor mode NAPOT pages"
+ default PLATFORM_MAY_SUPPORT_RISCV_ISA_SVNAPOT
+ help
+ This selects the level of support for Svnapot in the Linux Kernel.
+
+ The Svnapot extension is used to mark contiguous PTEs as a range
+ of contiguous virtual-to-physical translations for a naturally
+ aligned power-of-2 (NAPOT) granularity larger than the base 4KB page
+ size. When HUGETLBFS is also selected this option unconditionally
+ allocates some memory for each NAPOT page size supported by the kernel.
+ When optimizing for low memory consumption and for platforms without
+ the Svnapot extension, it may be better to prohibit Svnapot.
+
+config PROHIBIT_RISCV_ISA_SVNAPOT
+ bool "Prohibit Svnapot extension"
+ help
+ Regardless of if the platform supports Svnapot, prohibit the kernel
+ from using Svnapot.
+
+config PLATFORM_MAY_SUPPORT_RISCV_ISA_SVNAPOT
+ bool "Allow Svnapot extension if supported"
+ depends on 64BIT && MMU
+ depends on RISCV_ALTERNATIVE
+ select RISCV_ISA_SVNAPOT
+ help
+ Add support for the Svnapot ISA-extension in the kernel when it
+ is detected at boot.
+
+config PLATFORM_SUPPORTS_RISCV_ISA_SVNAPOT
+ bool "Emit Svnapot mappings when building Linux"
+ depends on 64BIT && MMU
+ depends on NONPORTABLE
+ select RISCV_ISA_SVNAPOT
+ help
+ Compile a kernel that assumes that the platform supports Svnapot.
+ This option produces a kernel that will not run on systems that do
+ not support Svnapot.
+
+endchoice
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 6afd6bb4882e..432be9691b78 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -289,7 +289,8 @@ static inline pte_t pud_pte(pud_t pud)
static __always_inline bool has_svnapot(void)
{
- return riscv_has_extension_likely(RISCV_ISA_EXT_SVNAPOT);
+ return IS_ENABLED(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_SVNAPOT) ||
+ riscv_has_extension_likely(RISCV_ISA_EXT_SVNAPOT);
}
static inline unsigned long pte_napot(pte_t pte)
--
2.44.0
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