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x86, realmode: Fix no cache bits test in reboot_32.S

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Before the new real-mode code infrastructure %edx was
used for testing CD and NW bits with andl in order to
decide whether to flush the processor caches or not.
The value of cr0 was also stored in %eax, which was
later used to set cr0 after masking out lower byte
(except TS bit) in order to enter real-mode.

In the new real-mode code infrastructure we wanted to
keep input parameter in %eax so we are using %edx for
both cr0 cases. This has caused regression since andl
overwrites the value of %edx.

This patch fixes the issue by replacing andl with testl,
which is essentially andl without writing result to the
register.

Special thanks to Paolo Bonzini for noting this and
proposing a fix.

Reported-and-tested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Link: http://lkml.kernel.org/r/1336633898-23743-1-git-send-email-jarkko.sakkinen@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Jarkko Sakkinen 2012-05-10 10:11:38 +03:00 committed by H. Peter Anvin
parent 0f6f11eb00
commit 34d0b02e08
1 changed files with 1 additions and 1 deletions
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2
arch/x86/realmode/rm/reboot_32.S
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@ -76,7 +76,7 @@ machine_real_restart_asm16:
movl %edx, %cr0
movl %ecx, %cr3
movl %cr0, %edx
andl $0x60000000, %edx /* If no cache bits -> no wbinvd */
testl $0x60000000, %edx /* If no cache bits -> no wbinvd */
jz 2f
wbinvd
2: