Subject: Re: [PATCH kernel v9 20/32] powerpc/powernv/ioda2: Introduce pnv_pci_create_table/pnv_pci_free_table

From: David Gibson <[email-masked]>
Date: Wed, 29 Apr 2015 14:39:49 +1000

On Sat, Apr 25, 2015 at 10:14:44PM +1000, Alexey Kardashevskiy wrote:
> This is a part of moving TCE table allocation into an iommu_ops
> callback to support multiple IOMMU groups per one VFIO container.
> 
> This moves a table creation window to the file with common powernv-pci
> helpers as it does not do anything IODA2-specific.
> 
> This adds pnv_pci_free_table() helper to release the actual TCE table.
> 
> This enforces window size to be a power of two.
> 
> This should cause no behavioural change.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> Reviewed-by: David Gibson <[email-masked]>
> ---
> Changes:
> v9:
> * moved helpers to the common powernv pci.c file from pci-ioda.c
> * moved bits from pnv_pci_create_table() to pnv_alloc_tce_table_pages()
> ---
>  arch/powerpc/platforms/powernv/pci-ioda.c | 36 ++++++------------
>  arch/powerpc/platforms/powernv/pci.c      | 61 +++++++++++++++++++++++++++++++
>  arch/powerpc/platforms/powernv/pci.h      |  4 ++
>  3 files changed, 76 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index a80be34..b9b3773 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1307,8 +1307,7 @@ static void pnv_pci_ioda2_release_dma_pe(struct pci_dev *dev, struct pnv_ioda_pe
>  	if (rc)
>  		pe_warn(pe, "OPAL error %ld release DMA window\n", rc);
>  
> -	iommu_reset_table(tbl, of_node_full_name(dev->dev.of_node));
> -	free_pages(addr, get_order(TCE32_TABLE_SIZE));
> +	pnv_pci_free_table(tbl);
>  }
>  
>  static void pnv_ioda_release_vf_PE(struct pci_dev *pdev, u16 num_vfs)
> @@ -2039,10 +2038,7 @@ static struct iommu_table_group_ops pnv_pci_ioda2_ops = {
>  static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>  				       struct pnv_ioda_pe *pe)
>  {
> -	struct page *tce_mem = NULL;
> -	void *addr;
>  	struct iommu_table *tbl = &pe->table_group.tables[0];
> -	unsigned int tce_table_size, end;
>  	int64_t rc;
>  
>  	/* We shouldn't already have a 32-bit DMA associated */
> @@ -2053,29 +2049,20 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>  
>  	/* The PE will reserve all possible 32-bits space */
>  	pe->tce32_seg = 0;
> -	end = (1 << ilog2(phb->ioda.m32_pci_base));
> -	tce_table_size = (end / 0x1000) * 8;
>  	pe_info(pe, "Setting up 32-bit TCE table at 0..%08x\n",
> -		end);
> +		phb->ioda.m32_pci_base);
>  
> -	/* Allocate TCE table */
> -	tce_mem = alloc_pages_node(phb->hose->node, GFP_KERNEL,
> -				   get_order(tce_table_size));
> -	if (!tce_mem) {
> -		pe_err(pe, "Failed to allocate a 32-bit TCE memory\n");
> -		goto fail;
> +	rc = pnv_pci_create_table(&pe->table_group, pe->phb->hose->node,
> +			0, IOMMU_PAGE_SHIFT_4K, phb->ioda.m32_pci_base, tbl);
> +	if (rc) {
> +		pe_err(pe, "Failed to create 32-bit TCE table, err %ld", rc);
> +		return;
>  	}
> -	addr = page_address(tce_mem);
> -	memset(addr, 0, tce_table_size);
> -
> -	/* Setup iommu */
> -	tbl->it_table_group = &pe->table_group;
> -
> -	/* Setup linux iommu table */
> -	pnv_pci_setup_iommu_table(tbl, addr, tce_table_size, 0,
> -			IOMMU_PAGE_SHIFT_4K);
>  
>  	tbl->it_ops = &pnv_ioda2_iommu_ops;
> +
> +	/* Setup iommu */
> +	tbl->it_table_group = &pe->table_group;
>  	iommu_init_table(tbl, phb->hose->node);
>  #ifdef CONFIG_IOMMU_API
>  	pe->table_group.ops = &pnv_pci_ioda2_ops;
> @@ -2121,8 +2108,7 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>  fail:
>  	if (pe->tce32_seg >= 0)
>  		pe->tce32_seg = -1;
> -	if (tce_mem)
> -		__free_pages(tce_mem, get_order(tce_table_size));
> +	pnv_pci_free_table(tbl);
>  }
>  
>  static void pnv_ioda_setup_dma(struct pnv_phb *phb)
> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> index e8802ac..6bcfad5 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -20,7 +20,9 @@
>  #include <linux/io.h>
>  #include <linux/msi.h>
>  #include <linux/iommu.h>
> +#include <linux/memblock.h>
>  
> +#include <asm/mmzone.h>
>  #include <asm/sections.h>
>  #include <asm/io.h>
>  #include <asm/prom.h>
> @@ -645,6 +647,65 @@ void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
>  	tbl->it_type = TCE_PCI;
>  }
>  
> +static __be64 *pnv_alloc_tce_table_pages(int nid, unsigned shift,
> +		unsigned long *tce_table_allocated)

I'm a bit confused by the tce_table_allocated parameter.  What's the
circumstance where more memory is requested than required, and why
does it matter to the caller?

> +{
> +	struct page *tce_mem = NULL;
> +	__be64 *addr;
> +	unsigned order = max_t(unsigned, shift, PAGE_SHIFT) - PAGE_SHIFT;
> +	unsigned long local_allocated = 1UL << (order + PAGE_SHIFT);
> +
> +	tce_mem = alloc_pages_node(nid, GFP_KERNEL, order);
> +	if (!tce_mem) {
> +		pr_err("Failed to allocate a TCE memory, order=%d\n", order);
> +		return NULL;
> +	}
> +	addr = page_address(tce_mem);
> +	memset(addr, 0, local_allocated);
> +	*tce_table_allocated = local_allocated;
> +
> +	return addr;
> +}
> +
> +long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
> +		__u64 bus_offset, __u32 page_shift, __u64 window_size,
> +		struct iommu_table *tbl)

The table_group parameter is redundant, isn't it?  It must be equal to
tbl->table_group, yes?

Or would it make more sense for this function to set
tbl->table_group?  And for that matter wouldn't it make more sense for
this to set it_size as well?

> +{
> +	void *addr;
> +	unsigned long tce_table_allocated = 0;
> +	const unsigned window_shift = ilog2(window_size);
> +	unsigned entries_shift = window_shift - page_shift;
> +	unsigned table_shift = entries_shift + 3;
> +	const unsigned long tce_table_size = max(0x1000UL, 1UL << table_shift);

So, here you round up to 4k, the in the alloc function you round up to
PAGE_SIZE (which may or may not be the same).  It's not clear to me why
there are two rounds of rounding up.

> +	if ((window_size > memory_hotplug_max()) || !is_power_of_2(window_size))
> +		return -EINVAL;
> +
> +	/* Allocate TCE table */
> +	addr = pnv_alloc_tce_table_pages(nid, table_shift,
> +			&tce_table_allocated);
> +
> +	/* Setup linux iommu table */
> +	pnv_pci_setup_iommu_table(tbl, addr, tce_table_size, bus_offset,
> +			page_shift);
> +
> +	pr_info("Created TCE table: window size = %08llx, "
> +			"tablesize = %lx (%lx), start @%08llx\n",
> +			window_size, tce_table_size, tce_table_allocated,
> +			bus_offset);
> +
> +	return 0;
> +}
> +
> +void pnv_pci_free_table(struct iommu_table *tbl)
> +{
> +	if (!tbl->it_size)
> +		return;
> +
> +	free_pages(tbl->it_base, get_order(tbl->it_size << 3));
> +	iommu_reset_table(tbl, "pnv");
> +}
> +
>  static void pnv_pci_dma_dev_setup(struct pci_dev *pdev)
>  {
>  	struct pci_controller *hose = pci_bus_to_host(pdev->bus);
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index b15cce5..e6cbbec 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -218,6 +218,10 @@ int pnv_pci_cfg_write(struct pci_dn *pdn,
>  extern void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
>  				      void *tce_mem, u64 tce_size,
>  				      u64 dma_offset, unsigned page_shift);
> +extern long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
> +		__u64 bus_offset, __u32 page_shift, __u64 window_size,
> +		struct iommu_table *tbl);
> +extern void pnv_pci_free_table(struct iommu_table *tbl);
>  extern void pnv_pci_init_p5ioc2_hub(struct device_node *np);
>  extern void pnv_pci_init_ioda_hub(struct device_node *np);
>  extern void pnv_pci_init_ioda2_phb(struct device_node *np);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson