On Tue, 1 Sep 2015, Richard W.M. Jones wrote:
> On Sun, Aug 30, 2015 at 10:37:57PM -0400, Chuck Ebbert wrote:
> > This is from https://bugzilla.redhat.com/show_bug.cgi?id=1258223
> >
> > [ 0.036000] BUG: unable to handle kernel paging request at 55501e06
> [...]
> > [ 0.036000] [<c0409c80>] ? add_nops+0x90/0xa0
> > [ 0.036000] [<c040a054>] apply_alternatives+0x274/0x630
> > [ 0.036000] [<c07f1cf0>] ? wait_for_xmitr+0xa0/0xa0
> > [ 0.036000] [<c071a6fc>] ? sprintf+0x1c/0x20
> > [ 0.036000] [<c0aae480>] ? irq_entries_start+0x698/0x698
> > [ 0.036000] [<c071be4b>] ? memcpy+0xb/0x30
> > [ 0.036000] [<c07f3950>] ? serial8250_set_termios+0x20/0x20
> [...]
> > Interrupt 0x30 occurred while the alternatives code was replacing the
> > initial 0x90,0x90,0x90 NOPs (from the ASM_CLAC macro) with the optimized
> > version, 0x8d,0x76,0x00. Only the first byte has been replaced so far,
> > and it makes a mess out of the insn decoding.
apply_alternatives() has two ways to modify the code:
1) text_poke_early()
2) optimize_nops()
The former disables interrupts, the latter not. The patch below should
fix the issue.
Thanks,
tglx
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index c42827eb86cf..6a2f93e029f4 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -257,6 +257,9 @@ void __init arch_init_ideal_nops(void)
/* Use this to add nops to a buffer, then text_poke the whole buffer. */
static void __init_or_module add_nops(void *insns, unsigned int len)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
while (len > 0) {
unsigned int noplen = len;
if (noplen > ASM_NOP_MAX)
@@ -265,6 +268,7 @@ static void __init_or_module add_nops(void *insns, unsigned
int len)
insns += noplen;
len -= noplen;
}
+ local_irq_restore(flags);
}
extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
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