linux-kernel - Re: [PATCH v4 11/16] powerpc/mm: Add hooks for cxl

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Message-ID: <87wq891d7y.fsf@linux.vnet.ibm.com>
Date:	Thu, 09 Oct 2014 20:50:49 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Michael Neuling <mikey@...ling.org>, greg@...ah.com, arnd@...db.de,
	mpe@...erman.id.au, benh@...nel.crashing.org
Cc:	mikey@...ling.org, anton@...ba.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, jk@...abs.org, imunsie@....ibm.com,
	cbe-oss-dev@...ts.ozlabs.org
Subject: Re: [PATCH v4 11/16] powerpc/mm: Add hooks for cxl

Michael Neuling <mikey@...ling.org> writes:

> From: Ian Munsie <imunsie@....ibm.com>
>
> This adds hooks into the core powerpc mm code for cxl.
>
> The core powerpc code sometimes uses local tlbie. Unfortunately this won't
> work with the current cxl driver as it relies on snooping tlbie broadcasts.
>
> The cxl hardware can have TLB entries invalidated via MMIO but this is not
> currently supported by the driver. In future we can make local tlbie smarter so
> that it invalidates cxl contexts via MMIO when it needs to but for now we have
> this workaround.
>
> This workaround checks for any active cxl contexts and if so, disables local
> tlbie.
>
> This also adds a hook for when SLBs are invalidated. This ensures any
> corresponding SLBs in cxl are also invalidated at the same time. This is
> required for segment demotion.
>
> Signed-off-by: Ian Munsie <imunsie@....ibm.com>
> Signed-off-by: Michael Neuling <mikey@...ling.org>
> ---
>  arch/powerpc/mm/copro_fault.c    | 2 ++
>  arch/powerpc/mm/hash_native_64.c | 6 +++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c
> index f2aa5a8..0f9939e 100644
> --- a/arch/powerpc/mm/copro_fault.c
> +++ b/arch/powerpc/mm/copro_fault.c
> @@ -26,6 +26,7 @@
>  #include <asm/reg.h>
>  #include <asm/copro.h>
>  #include <asm/spu.h>
> +#include <misc/cxl.h>
>  
>  /*
>   * This ought to be kept in sync with the powerpc specific do_page_fault
> @@ -143,5 +144,6 @@ void copro_flush_all_slbs(struct mm_struct *mm)
>  #ifdef CONFIG_SPU_BASE
>  	spu_flush_all_slbs(mm);
>  #endif
> +	cxl_slbia(mm);
>  }

If you split this patch into two and move the above hunk in a patch
before "[PATCH v4 09/16] powerpc/mm: Add new hash_page_mm()", it would
make it much easier to follow. We could then update the commit of the
09th patch to carry additional information that talk about how the
hash_page_mm really work as I replied to that patch.


>  EXPORT_SYMBOL_GPL(copro_flush_all_slbs);
> diff --git a/arch/powerpc/mm/hash_native_64.c b/arch/powerpc/mm/hash_native_64.c
> index afc0a82..ae4962a 100644
> --- a/arch/powerpc/mm/hash_native_64.c
> +++ b/arch/powerpc/mm/hash_native_64.c
> @@ -29,6 +29,8 @@
>  #include <asm/kexec.h>
>  #include <asm/ppc-opcode.h>
>  
> +#include <misc/cxl.h>
> +
>  #ifdef DEBUG_LOW
>  #define DBG_LOW(fmt...) udbg_printf(fmt)
>  #else
> @@ -149,9 +151,11 @@ static inline void __tlbiel(unsigned long vpn, int psize, int apsize, int ssize)
>  static inline void tlbie(unsigned long vpn, int psize, int apsize,
>  			 int ssize, int local)
>  {
> -	unsigned int use_local = local && mmu_has_feature(MMU_FTR_TLBIEL);
> +	unsigned int use_local;
>  	int lock_tlbie = !mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE);
>  
> +	use_local = local && mmu_has_feature(MMU_FTR_TLBIEL) && !cxl_ctx_in_use();
> +
>  	if (use_local)
>  		use_local = mmu_psize_defs[psize].tlbiel;
>  	if (lock_tlbie && !use_local)
> -- 
> 1.9.1
>
> --
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