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Date:   Sat, 22 Aug 2020 19:33:47 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Joel Stanley <joel@....id.au>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>,
        Brian King <brking@...ux.vnet.ibm.com>,
        Murilo Fossa Vicentini <muvic@...ux.ibm.com>,
        David Dai <zdai@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 01/10] powerpc/pseries/iommu: Replace hard-coded page
 shift



On 18/08/2020 09:40, Leonardo Bras wrote:
> Some functions assume IOMMU page size can only be 4K (pageshift == 12).
> Update them to accept any page size passed, so we can use 64K pages.
> 
> In the process, some defines like TCE_SHIFT were made obsolete, and then
> removed. TCE_RPN_MASK was updated to generate a mask according to
> the pageshift used.
> 
> Most places had a tbl struct, so using tbl->it_page_shift was simple.
> tce_free_pSeriesLP() was a special case, since callers not always have a
> tbl struct, so adding a tceshift parameter seems the right thing to do.
> 
> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> ---
>  arch/powerpc/include/asm/tce.h         | 10 ++----
>  arch/powerpc/platforms/pseries/iommu.c | 42 ++++++++++++++++----------
>  2 files changed, 28 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/tce.h b/arch/powerpc/include/asm/tce.h
> index db5fc2f2262d..971cba2d87cc 100644
> --- a/arch/powerpc/include/asm/tce.h
> +++ b/arch/powerpc/include/asm/tce.h
> @@ -19,15 +19,9 @@
>  #define TCE_VB			0
>  #define TCE_PCI			1
>  
> -/* TCE page size is 4096 bytes (1 << 12) */
> -
> -#define TCE_SHIFT	12
> -#define TCE_PAGE_SIZE	(1 << TCE_SHIFT)
> -
>  #define TCE_ENTRY_SIZE		8		/* each TCE is 64 bits */
> -
> -#define TCE_RPN_MASK		0xfffffffffful  /* 40-bit RPN (4K pages) */
> -#define TCE_RPN_SHIFT		12
> +#define TCE_RPN_BITS		52		/* Bits 0-51 represent RPN on TCE */


Ditch this one and use MAX_PHYSMEM_BITS instead? I am pretty sure this
is the actual limit.


> +#define TCE_RPN_MASK(ps)	((1ul << (TCE_RPN_BITS - (ps))) - 1)
>  #define TCE_VALID		0x800		/* TCE valid */
>  #define TCE_ALLIO		0x400		/* TCE valid for all lpars */
>  #define TCE_PCI_WRITE		0x2		/* write from PCI allowed */
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index e4198700ed1a..8fe23b7dff3a 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -107,6 +107,9 @@ static int tce_build_pSeries(struct iommu_table *tbl, long index,
>  	u64 proto_tce;
>  	__be64 *tcep;
>  	u64 rpn;
> +	const unsigned long tceshift = tbl->it_page_shift;
> +	const unsigned long pagesize = IOMMU_PAGE_SIZE(tbl);
> +	const u64 rpn_mask = TCE_RPN_MASK(tceshift);

Using IOMMU_PAGE_SIZE macro for the page size and not using
IOMMU_PAGE_MASK for the mask - this incosistency makes my small brain
explode :) I understand the history but maaaaan... Oh well, ok.

Good, otherwise. Thanks,

>  
>  	proto_tce = TCE_PCI_READ; // Read allowed
>  
> @@ -117,10 +120,10 @@ static int tce_build_pSeries(struct iommu_table *tbl, long index,
>  
>  	while (npages--) {
>  		/* can't move this out since we might cross MEMBLOCK boundary */
> -		rpn = __pa(uaddr) >> TCE_SHIFT;
> -		*tcep = cpu_to_be64(proto_tce | (rpn & TCE_RPN_MASK) << TCE_RPN_SHIFT);
> +		rpn = __pa(uaddr) >> tceshift;
> +		*tcep = cpu_to_be64(proto_tce | (rpn & rpn_mask) << tceshift);
>  
> -		uaddr += TCE_PAGE_SIZE;
> +		uaddr += pagesize;
>  		tcep++;
>  	}
>  	return 0;
> @@ -146,7 +149,7 @@ static unsigned long tce_get_pseries(struct iommu_table *tbl, long index)
>  	return be64_to_cpu(*tcep);
>  }
>  
> -static void tce_free_pSeriesLP(unsigned long liobn, long, long);
> +static void tce_free_pSeriesLP(unsigned long liobn, long, long, long);
>  static void tce_freemulti_pSeriesLP(struct iommu_table*, long, long);
>  
>  static int tce_build_pSeriesLP(unsigned long liobn, long tcenum, long tceshift,
> @@ -159,6 +162,7 @@ static int tce_build_pSeriesLP(unsigned long liobn, long tcenum, long tceshift,
>  	u64 rpn;
>  	int ret = 0;
>  	long tcenum_start = tcenum, npages_start = npages;
> +	const u64 rpn_mask = TCE_RPN_MASK(tceshift);
>  
>  	rpn = __pa(uaddr) >> tceshift;
>  	proto_tce = TCE_PCI_READ;
> @@ -166,12 +170,12 @@ static int tce_build_pSeriesLP(unsigned long liobn, long tcenum, long tceshift,
>  		proto_tce |= TCE_PCI_WRITE;
>  
>  	while (npages--) {
> -		tce = proto_tce | (rpn & TCE_RPN_MASK) << tceshift;
> +		tce = proto_tce | (rpn & rpn_mask) << tceshift;
>  		rc = plpar_tce_put((u64)liobn, (u64)tcenum << tceshift, tce);
>  
>  		if (unlikely(rc == H_NOT_ENOUGH_RESOURCES)) {
>  			ret = (int)rc;
> -			tce_free_pSeriesLP(liobn, tcenum_start,
> +			tce_free_pSeriesLP(liobn, tcenum_start, tceshift,
>  			                   (npages_start - (npages + 1)));
>  			break;
>  		}
> @@ -205,10 +209,12 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
>  	long tcenum_start = tcenum, npages_start = npages;
>  	int ret = 0;
>  	unsigned long flags;
> +	const unsigned long tceshift = tbl->it_page_shift;
> +	const u64 rpn_mask = TCE_RPN_MASK(tceshift);
>  
>  	if ((npages == 1) || !firmware_has_feature(FW_FEATURE_PUT_TCE_IND)) {
>  		return tce_build_pSeriesLP(tbl->it_index, tcenum,
> -					   tbl->it_page_shift, npages, uaddr,
> +					   tceshift, npages, uaddr,
>  		                           direction, attrs);
>  	}
>  
> @@ -225,13 +231,13 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
>  		if (!tcep) {
>  			local_irq_restore(flags);
>  			return tce_build_pSeriesLP(tbl->it_index, tcenum,
> -					tbl->it_page_shift,
> +					tceshift,
>  					npages, uaddr, direction, attrs);
>  		}
>  		__this_cpu_write(tce_page, tcep);
>  	}
>  
> -	rpn = __pa(uaddr) >> TCE_SHIFT;
> +	rpn = __pa(uaddr) >> tceshift;
>  	proto_tce = TCE_PCI_READ;
>  	if (direction != DMA_TO_DEVICE)
>  		proto_tce |= TCE_PCI_WRITE;
> @@ -245,12 +251,12 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
>  		limit = min_t(long, npages, 4096/TCE_ENTRY_SIZE);
>  
>  		for (l = 0; l < limit; l++) {
> -			tcep[l] = cpu_to_be64(proto_tce | (rpn & TCE_RPN_MASK) << TCE_RPN_SHIFT);
> +			tcep[l] = cpu_to_be64(proto_tce | (rpn & rpn_mask) << tceshift);
>  			rpn++;
>  		}
>  
>  		rc = plpar_tce_put_indirect((u64)tbl->it_index,
> -					    (u64)tcenum << 12,
> +					    (u64)tcenum << tceshift,
>  					    (u64)__pa(tcep),
>  					    limit);
>  
> @@ -277,12 +283,13 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
>  	return ret;
>  }
>  
> -static void tce_free_pSeriesLP(unsigned long liobn, long tcenum, long npages)
> +static void tce_free_pSeriesLP(unsigned long liobn, long tcenum, long tceshift,
> +			       long npages)
>  {
>  	u64 rc;
>  
>  	while (npages--) {
> -		rc = plpar_tce_put((u64)liobn, (u64)tcenum << 12, 0);
> +		rc = plpar_tce_put((u64)liobn, (u64)tcenum << tceshift, 0);
>  
>  		if (rc && printk_ratelimit()) {
>  			printk("tce_free_pSeriesLP: plpar_tce_put failed. rc=%lld\n", rc);
> @@ -301,9 +308,11 @@ static void tce_freemulti_pSeriesLP(struct iommu_table *tbl, long tcenum, long n
>  	u64 rc;
>  
>  	if (!firmware_has_feature(FW_FEATURE_STUFF_TCE))
> -		return tce_free_pSeriesLP(tbl->it_index, tcenum, npages);
> +		return tce_free_pSeriesLP(tbl->it_index, tcenum,
> +					  tbl->it_page_shift, npages);
>  
> -	rc = plpar_tce_stuff((u64)tbl->it_index, (u64)tcenum << 12, 0, npages);
> +	rc = plpar_tce_stuff((u64)tbl->it_index,
> +			     (u64)tcenum << tbl->it_page_shift, 0, npages);
>  
>  	if (rc && printk_ratelimit()) {
>  		printk("tce_freemulti_pSeriesLP: plpar_tce_stuff failed\n");
> @@ -319,7 +328,8 @@ static unsigned long tce_get_pSeriesLP(struct iommu_table *tbl, long tcenum)
>  	u64 rc;
>  	unsigned long tce_ret;
>  
> -	rc = plpar_tce_get((u64)tbl->it_index, (u64)tcenum << 12, &tce_ret);
> +	rc = plpar_tce_get((u64)tbl->it_index,
> +			   (u64)tcenum << tbl->it_page_shift, &tce_ret);
>  
>  	if (rc && printk_ratelimit()) {
>  		printk("tce_get_pSeriesLP: plpar_tce_get failed. rc=%lld\n", rc);
> 

-- 
Alexey

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