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SubjectRe: [PATCH] parisc: Remove PTE load and fault check from L2_ptep macro
Hi,

On Sun, Sep 23, 2018 at 10:55:18AM -0400, John David Anglin wrote:
> This change removes the PTE load and present check from the L2_ptep
> macro. The load and check for kernel pages is now done in the tlb_lock
> macro. This avoids a double load and check for user pages. The load
> and check for user pages is now done inside the lock so the fault
> handler can't be called while the entry is being updated.
>

This patch causes my parisc qemu tests to fail.
Unfortunately I don't have any useful log output; the failure
is silent. Reverting the patch fixes the problem.

Guenter

> Signed-off-by: John David Anglin <dave.anglin@bell.net>
> Signed-off-by: Helge Deller <deller@gmx.de>
> ---
> arch/parisc/kernel/entry.S | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
> index eeee1d2c4b8e..3371472379a6 100644
> --- a/arch/parisc/kernel/entry.S
> +++ b/arch/parisc/kernel/entry.S
> @@ -431,8 +431,6 @@
> extru \va,31-PAGE_SHIFT,ASM_BITS_PER_PTE,\index
> dep %r0,31,PAGE_SHIFT,\pmd /* clear offset */
> shladd \index,BITS_PER_PTE_ENTRY,\pmd,\pmd /* pmd is now pte */
> - LDREG %r0(\pmd),\pte
> - bb,>=,n \pte,_PAGE_PRESENT_BIT,\fault
> .endm
>
> /* Look up PTE in a 3-Level scheme.
> @@ -463,7 +461,7 @@
> L2_ptep \pgd,\pte,\index,\va,\fault
> .endm
>
> - /* Acquire pa_tlb_lock lock and recheck page is still present. */
> + /* Acquire pa_tlb_lock lock and check page is present. */
> .macro tlb_lock spc,ptp,pte,tmp,tmp1,fault
> #ifdef CONFIG_SMP
> cmpib,COND(=),n 0,\spc,2f
> @@ -472,10 +470,12 @@
> cmpib,COND(=) 0,\tmp1,1b
> nop
> LDREG 0(\ptp),\pte
> - bb,<,n \pte,_PAGE_PRESENT_BIT,2f
> + bb,<,n \pte,_PAGE_PRESENT_BIT,3f
> b \fault
> stw \spc,0(\tmp)
> -2:
> +2: LDREG 0(\ptp),\pte
> + bb,>=,n \pte,_PAGE_PRESENT_BIT,\fault
> +3:
> #endif
> .endm
>
> --
> 2.7.4

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