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ARM, arm64: kvm: get rid of the bounce page

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The HYP init bounce page is a runtime construct that ensures that the
HYP init code does not cross a page boundary. However, this is something
we can do perfectly well at build time, by aligning the code appropriately.

For arm64, we just align to 4 KB, and enforce that the code size is less
than 4 KB, regardless of the chosen page size.

For ARM, the whole code is less than 256 bytes, so we tweak the linker
script to align at a power of 2 upper bound of the code size

Note that this also fixes a benign off-by-one error in the original bounce
page code, where a bounce page would be allocated unnecessarily if the code
was exactly 1 page in size.

On ARM, it also fixes an issue with very large kernels reported by Arnd
Bergmann, where stub sections with linker emitted veneers could erroneously
trigger the size/alignment ASSERT() in the linker script.

Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Ard Biesheuvel
2015-03-19 16:42:26 +00:00
committed by Will Deacon
parent 06e5801b8c
commit 06f75a1f62
4 changed files with 34 additions and 46 deletions
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18
arch/arm/kernel/vmlinux.lds.S
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@@ -23,11 +23,20 @@
VMLINUX_SYMBOL(__idmap_text_start) = .; \
*(.idmap.text) \
VMLINUX_SYMBOL(__idmap_text_end) = .; \
. = ALIGN(32); \
. = ALIGN(1 << LOG2CEIL(__hyp_idmap_size)); \
VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
*(.hyp.idmap.text) \
VMLINUX_SYMBOL(__hyp_idmap_text_end) = .;
/*
* If the HYP idmap .text section is populated, it needs to be positioned
* such that it will not cross a page boundary in the final output image.
* So align it to the section size rounded up to the next power of 2.
* If __hyp_idmap_size is undefined, the section will be empty so define
* it as 0 in that case.
*/
PROVIDE(__hyp_idmap_size = 0);
#ifdef CONFIG_HOTPLUG_CPU
#define ARM_CPU_DISCARD(x)
#define ARM_CPU_KEEP(x) x
@@ -346,8 +355,11 @@ SECTIONS
*/
ASSERT((__proc_info_end - __proc_info_begin), "missing CPU support")
ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined")
/*
* The HYP init code can't be more than a page long.
* The HYP init code can't be more than a page long,
* and should not cross a page boundary.
* The above comment applies as well.
*/
ASSERT(((__hyp_idmap_text_end - __hyp_idmap_text_start) <= PAGE_SIZE), "HYP init code too big")
ASSERT((__hyp_idmap_text_start & ~PAGE_MASK) + __hyp_idmap_size <= PAGE_SIZE,
"HYP init code too big or misaligned")