Re: [PATCH] x86, setup: add __flush_tlb() for Intel Quark X1000
From: Bryan O'Donoghue
Date: Fri Sep 26 2014 - 13:22:32 EST
On 26/09/14 16:00, Bryan O'Donoghue wrote:
+ * Locate the page directory and flush the TLB.
+ * On Quark X1000 CPUs we still have the PGE bit incorrectly set
+ * due to a processor erratum, so __flush_tlb_all() is not yet
+ * doing what it says. Fortunately we have a cr3 flush here,
+ * which is what is needed in this processor to flush TLBs, so
+ * there's no need to add a Quark X1000 quirk here.
+ * early_init_intel will unset the X86_FEATURE_PGE flag later
+ * and __flush_tlb_all() will flush via cr3
With the extra __flush_tlb(); on the end.
ACK Ong Boon Leong's patch
At the risk of contradicting myself in public I had a think about this
on the drive home and ...
As I see it - the reload @ CR3 should have flushed the TLB. That's what
the documentation says.
Right now with the proposed patch from Ong Boon Leong the code will be
While there may be no *harm* in adding an extra __flush_tlb(); - there's
not much *sense* in it either.
If however there's a strong feeling that an explicit __flush_tlb() is
required in Quark's case then - I believe the code should revert to the
original logic from the Quark BSP namely.
+ if (boot_cpu_data.x86 == 5 && boot_cpu_data.x86_model == 9)
This was Peter's initial suggestion in any case and as I see it the
right-thing-to-do rather than have another reduntant __flush_tlb() for
everybody who's not Quark.
How does that make sense ?
I can't imagine it's preferable to do a __flush_tlb(); on *x86 for the
sake of skipping an if/else
I'll resubmit that now with Ong Boon's commentary.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/