This was marked for stable, and honestly, nowhere in the discussion
did I see any mention of just *how* bad the performance impact of this
was.
When performance goes down by 50% on some loads, people need to start
asking themselves whether it was worth it. It's apparently better to
just disable SMT entirely, which is what security-conscious people do
anyway.
So why do that STIBP slow-down by default when the people who *really*
care already disabled SMT?
I think we should use the same logic as for L1TF: we default to
something that doesn't kill performance. Warn once about it, and let
the crazy people say "I'd rather take a 50% performance hit than
worry about a theoretical issue".
Linus
KEXEC needs the new kernel's load address to be aligned on a page
boundary (see sanity_check_segment_list()), but on MIPS the default
vmlinuz load address is only explicitly aligned to 16 bytes.
Since the largest PAGE_SIZE supported by MIPS kernels is 64KB, increase
the alignment calculated by calc_vmlinuz_load_addr to 64KB.
Cc: <stable(a)vger.kernel.org> # 2.6.36+
Signed-off-by: Huacai Chen <chenhc(a)lemote.com>
---
arch/mips/boot/compressed/calc_vmlinuz_load_addr.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/mips/boot/compressed/calc_vmlinuz_load_addr.c b/arch/mips/boot/compressed/calc_vmlinuz_load_addr.c
index 37fe58c..542c3ed 100644
--- a/arch/mips/boot/compressed/calc_vmlinuz_load_addr.c
+++ b/arch/mips/boot/compressed/calc_vmlinuz_load_addr.c
@@ -13,6 +13,7 @@
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
+#include "../../../../include/linux/sizes.h"
int main(int argc, char *argv[])
{
@@ -45,11 +46,11 @@ int main(int argc, char *argv[])
vmlinuz_load_addr = vmlinux_load_addr + vmlinux_size;
/*
- * Align with 16 bytes: "greater than that used for any standard data
- * types by a MIPS compiler." -- See MIPS Run Linux (Second Edition).
+ * Align with 64KB: KEXEC needs load sections to be aligned to PAGE_SIZE,
+ * which may be as large as 64KB depending on the kernel configuration.
*/
- vmlinuz_load_addr += (16 - vmlinux_size % 16);
+ vmlinuz_load_addr += (SZ_64K - vmlinux_size % SZ_64K);
printf("0x%llx\n", vmlinuz_load_addr);
--
2.7.0