Re: [PATCH v2 2/3] ppc64: Avoid rfid if no need to clear MSR_LE
From: Sam Mendoza-Jonas <hidden>
Date: 2015-11-02 00:22:46
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On Mon, Nov 02, 2015 at 09:55:53AM +1100, Sam Mendoza-Jonas wrote:
On Tue, Oct 06, 2015 at 05:55:49PM -0500, Scott Wood wrote:quoted
Commit a304e2d82a8c3 ("ppc64: purgatory: Reset primary cpu endian to big-endian) changed bctr to rfid. rfid is book3s-only and will cause a fatal exception on book3e. Purgatory is an isolated environment which makes importing information about the subarch awkward, so instead rely on the fact that MSR_LE should never be set on book3e, and the rfid is only needed if MSR_LE is set (and thus needs to be cleared). In theory that MSR bit is reserved on book3e, rather than zero, but in practice I have not seen it set. Signed-off-by: Scott Wood <redacted> Cc: Samuel Mendoza-Jonas <redacted> --- v2: new patchLooks good to me, thanks for catching this! I'll ping Michael too if you'd like his reviewed-by. Reviewed-by: Samuel Mendoza-Jonas <redacted>
Following up, also add my Tested-by: Samuel Mendoza-Jonas <redacted>
quoted
purgatory/arch/ppc64/v2wrap.S | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)diff --git a/purgatory/arch/ppc64/v2wrap.S b/purgatory/arch/ppc64/v2wrap.S index 179ade9..3534080 100644 --- a/purgatory/arch/ppc64/v2wrap.S +++ b/purgatory/arch/ppc64/v2wrap.S@@ -116,9 +116,17 @@ master: stw 7,0x5c(4) # and patch it into the kernel mr 3,16 # restore dt address + mfmsr 5 + andi. 10,5,1 # test MSR_LE + bne little_endian + + li 5,0 # r5 will be 0 for kernel + mtctr 4 # prepare branch to + bctr # start kernel + +little_endian: # book3s-only mtsrr0 4 # prepare branch to - mfmsr 5 clrrdi 5,5,1 # clear MSR_LE mtsrr1 5-- 2.1.4_______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev