From: Ard Biesheuvel <ardb@google.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH v7 6/7] arm64: mm: Reclaim unused vmemmap region for vmalloc use
Date: Wed, 13 Dec 2023 09:40:31 +0100 [thread overview]
Message-ID: <20231213084024.2367360-15-ardb@google.com> (raw)
In-Reply-To: <20231213084024.2367360-9-ardb@google.com>
From: Ard Biesheuvel <ardb@kernel.org>
The vmemmap array is statically sized based on the maximum supported
size of the virtual address space, but it is located inside the upper VA
region, which is statically sized based on the *minimum* supported size
of the VA space. This doesn't matter much when using 64k pages, which is
the only configuration that currently supports 52-bit virtual
addressing.
However, upcoming LPA2 support will change this picture somewhat, as in
that case, the vmemmap array will take up more than 25% of the upper VA
region when using 4k pages. Given that most of this space is never used
when running on a system that does not support 52-bit virtual
addressing, let's reclaim the unused vmemmap area in that case.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/include/asm/pgtable.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 8d30e2787b1f..5b5bedfa320e 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -18,11 +18,15 @@
* VMALLOC range.
*
* VMALLOC_START: beginning of the kernel vmalloc space
- * VMALLOC_END: extends to the available space below vmemmap, PCI I/O space
- * and fixed mappings
+ * VMALLOC_END: extends to the available space below vmemmap
*/
#define VMALLOC_START (MODULES_END)
+#if VA_BITS == VA_BITS_MIN
#define VMALLOC_END (VMEMMAP_START - SZ_8M)
+#else
+#define VMEMMAP_UNUSED_NPAGES ((_PAGE_OFFSET(vabits_actual) - PAGE_OFFSET) >> PAGE_SHIFT)
+#define VMALLOC_END (VMEMMAP_START + VMEMMAP_UNUSED_NPAGES * sizeof(struct page) - SZ_8M)
+#endif
#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
--
2.43.0.472.g3155946c3a-goog
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next prev parent reply other threads:[~2023-12-13 8:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-13 8:40 [PATCH v7 0/7] arm64: Reorganize kernel VA space Ard Biesheuvel
2023-12-13 8:40 ` [PATCH v7 1/7] arm64: mm: Move PCI I/O emulation region above the vmemmap region Ard Biesheuvel
2023-12-13 8:40 ` [PATCH v7 2/7] arm64: mm: Move fixmap region above " Ard Biesheuvel
2023-12-13 8:40 ` [PATCH v7 3/7] arm64: ptdump: Allow all region boundaries to be defined at boot time Ard Biesheuvel
2023-12-13 8:40 ` [PATCH v7 4/7] arm64: ptdump: Discover start of vmemmap region at runtime Ard Biesheuvel
2023-12-13 8:40 ` [PATCH v7 5/7] arm64: vmemmap: Avoid base2 order of struct page size to dimension region Ard Biesheuvel
2023-12-13 13:49 ` Mark Rutland
2023-12-13 14:09 ` Ard Biesheuvel
2023-12-13 14:39 ` Mark Rutland
2024-02-09 17:33 ` Catalin Marinas
2023-12-13 8:40 ` Ard Biesheuvel [this message]
2023-12-13 8:40 ` [PATCH v7 7/7] arm64: kaslr: Adjust randomization range dynamically Ard Biesheuvel
2024-02-09 17:33 ` [PATCH v7 0/7] arm64: Reorganize kernel VA space Catalin Marinas
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