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| author | Anton Ivanov <anton.ivanov@cambridgegreys.com> | 2019-01-04 18:38:21 +0300 |
|---|---|---|
| committer | Richard Weinberger <richard@nod.at> | 2019-05-08 00:18:28 +0300 |
| commit | 5c2ffce1e9496477720966e70d79f2da3e4b84e6 (patch) | |
| tree | 12e77ce3c8debd687029236435ea5f3f7fbfdf70 /arch/um/Kconfig | |
| parent | 37624b58542fb9f2d9a70e6ea006ef8a5f66c30b (diff) | |
| download | linux-5c2ffce1e9496477720966e70d79f2da3e4b84e6.tar.xz | |
um: Revert to using stack for pt_regs in signal handling
Reverts commit b6024b21fec8367ef961a771cc9dde31f1831965 and
adjusts default stack sizing to cope with larger size of
floating point save registers on the newer Intel CPUs.
b6024b21fec8367ef961a771cc9dde31f1831965 replaced storing the
register state on the stack with kmalloc-ed storage. That has
a number of issues and a panic if that fails.
1. kmalloc/ATOMIC can fail. There was a latent hard crash
in all interrupt and fault handling as a result.
2. kmalloc in the interrupt path introduces a considerable
performance penalty for networking ~ 14% on iperf.
This commit restores uml to a stable state until a better
solution is found.
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch/um/Kconfig')
| -rw-r--r-- | arch/um/Kconfig | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/arch/um/Kconfig b/arch/um/Kconfig index ec9711d068b7..41913504a56e 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -142,13 +142,17 @@ config MAGIC_SYSRQ config KERNEL_STACK_ORDER int "Kernel stack size order" - default 1 if 64BIT - range 1 10 if 64BIT - default 0 if !64BIT + default 2 if 64BIT + range 2 10 if 64BIT + default 1 if !64BIT help This option determines the size of UML kernel stacks. They will be 1 << order pages. The default is OK unless you're running Valgrind on UML, in which case, set this to 3. + It is possible to reduce the stack to 1 for 64BIT and 0 for 32BIT on + older (pre-2017) CPUs. It is not recommended on newer CPUs due to the + increase in the size of the state which needs to be saved when handling + signals. config MMAPPER tristate "iomem emulation driver" |