Message-ID: <Zfm6TKhBmqDfvxs4@lizhi-Precision-Tower-5810>
Date: Tue, 19 Mar 2024 12:16:12 -0400
From: Frank Li <Frank.li@....com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: endpoint: Migrate to Genalloc framework for
 outbound window memory allocation

On Tue, Mar 19, 2024 at 11:50:50AM -0400, Frank Li wrote:
> On Sun, Mar 17, 2024 at 11:39:17AM +0530, Manivannan Sadhasivam wrote:
> > As proposed during the last year 'PCI Endpoint Subsystem Open Items
> > Discussion' of Linux Plumbers conference [1], let's migrate to Genalloc
> > framework for managing the endpoint outbound window memory allocation.
> > 
> > PCI Endpoint subsystem is using a custom memory allocator in pci-epc-mem
> > driver from the start for managing the memory required to map the host
> > address space (outbound) in endpoint. Even though it works well, it
> > completely defeats the purpose of the 'Genalloc framework', a general
> > purpose memory allocator framework created to avoid various custom memory
> > allocators in the kernel.
> > 
> > The migration to Genalloc framework is done is such a way that the existing
> > API semantics are preserved. So that the callers of the EPC mem APIs do not
> > need any modification (apart from the pcie-designware-epc driver that
> > queries page size).
> > 
> > Internally, the EPC mem driver now uses Genalloc framework's
> > 'gen_pool_first_fit_order_align' algorithm that aligns the allocated memory
> > based on the requested size as like the previous allocator. And the
> > page size passed during pci_epc_mem_init() API is used as the minimum order
> > for the memory allocations.
> > 
> > During the migration, 'struct pci_epc_mem' is removed as it is seems
> > redundant and the existing 'struct pci_epc_mem_window' in 'struct pci_epc'
> > is now used to hold the address windows of the endpoint controller.
> > 
> > [1] https://lpc.events/event/17/contributions/1419/
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-ep.c |  14 +-
> >  drivers/pci/endpoint/pci-epc-mem.c              | 182 +++++++++---------------
> >  include/linux/pci-epc.h                         |  25 +---
> >  3 files changed, 81 insertions(+), 140 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > index 5befed2dc02b..37c612282eb6 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > @@ -482,11 +482,11 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
> >  		reg = ep_func->msi_cap + PCI_MSI_DATA_32;
> >  		msg_data = dw_pcie_ep_readw_dbi(ep, func_no, reg);
> >  	}
> > -	aligned_offset = msg_addr_lower & (epc->mem->window.page_size - 1);
> > +	aligned_offset = msg_addr_lower & (epc->windows[0]->page_size - 1);
> >  	msg_addr = ((u64)msg_addr_upper) << 32 |
> >  			(msg_addr_lower & ~aligned_offset);
> >  	ret = dw_pcie_ep_map_addr(epc, func_no, 0, ep->msi_mem_phys, msg_addr,
> > -				  epc->mem->window.page_size);
> > +				  epc->windows[0]->page_size);
> >  	if (ret)
> >  		return ret;
> >  
> > @@ -550,10 +550,10 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
> >  		return -EPERM;
> >  	}
> >  
> > -	aligned_offset = msg_addr & (epc->mem->window.page_size - 1);
> > +	aligned_offset = msg_addr & (epc->windows[0]->page_size - 1);
> >  	msg_addr &= ~aligned_offset;
> >  	ret = dw_pcie_ep_map_addr(epc, func_no, 0, ep->msi_mem_phys, msg_addr,
> > -				  epc->mem->window.page_size);
> > +				  epc->windows[0]->page_size);
> >  	if (ret)
> >  		return ret;
> >  
> > @@ -572,7 +572,7 @@ void dw_pcie_ep_exit(struct dw_pcie_ep *ep)
> >  	dw_pcie_edma_remove(pci);
> >  
> >  	pci_epc_mem_free_addr(epc, ep->msi_mem_phys, ep->msi_mem,
> > -			      epc->mem->window.page_size);
> > +			      epc->windows[0]->page_size);
> >  
> >  	pci_epc_mem_exit(epc);
> >  
> > @@ -742,7 +742,7 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> >  	}
> >  
> >  	ep->msi_mem = pci_epc_mem_alloc_addr(epc, &ep->msi_mem_phys,
> > -					     epc->mem->window.page_size);
> > +					     epc->windows[0]->page_size);
> >  	if (!ep->msi_mem) {
> >  		ret = -ENOMEM;
> >  		dev_err(dev, "Failed to reserve memory for MSI/MSI-X\n");
> > @@ -770,7 +770,7 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> >  
> >  err_free_epc_mem:
> >  	pci_epc_mem_free_addr(epc, ep->msi_mem_phys, ep->msi_mem,
> > -			      epc->mem->window.page_size);
> > +			      epc->windows[0]->page_size);
> >  
> >  err_exit_epc_mem:
> >  	pci_epc_mem_exit(epc);
> > diff --git a/drivers/pci/endpoint/pci-epc-mem.c b/drivers/pci/endpoint/pci-epc-mem.c
> > index a9c028f58da1..f9e6e1a6aeaa 100644
> > --- a/drivers/pci/endpoint/pci-epc-mem.c
> > +++ b/drivers/pci/endpoint/pci-epc-mem.c
> > @@ -4,37 +4,18 @@
> >   *
> >   * Copyright (C) 2017 Texas Instruments
> >   * Author: Kishon Vijay Abraham I <kishon@...com>
> > + *
> > + * Copyright (C) 2024 Linaro Ltd.
> > + * Author: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> >   */
> >  
> > +#include <linux/genalloc.h>
> >  #include <linux/io.h>
> >  #include <linux/module.h>
> >  #include <linux/slab.h>
> >  
> >  #include <linux/pci-epc.h>
> >  
> > -/**
> > - * pci_epc_mem_get_order() - determine the allocation order of a memory size
> > - * @mem: address space of the endpoint controller
> > - * @size: the size for which to get the order
> > - *
> > - * Reimplement get_order() for mem->page_size since the generic get_order
> > - * always gets order with a constant PAGE_SIZE.
> > - */
> > -static int pci_epc_mem_get_order(struct pci_epc_mem *mem, size_t size)
> > -{
> > -	int order;
> > -	unsigned int page_shift = ilog2(mem->window.page_size);
> > -
> > -	size--;
> > -	size >>= page_shift;
> > -#if BITS_PER_LONG == 32
> > -	order = fls(size);
> > -#else
> > -	order = fls64(size);
> > -#endif
> > -	return order;
> > -}
> > -
> >  /**
> >   * pci_epc_multi_mem_init() - initialize the pci_epc_mem structure
> >   * @epc: the EPC device that invoked pci_epc_mem_init
> > @@ -48,17 +29,11 @@ int pci_epc_multi_mem_init(struct pci_epc *epc,
> >  			   struct pci_epc_mem_window *windows,
> >  			   unsigned int num_windows)
> >  {
> > -	struct pci_epc_mem *mem = NULL;
> > -	unsigned long *bitmap = NULL;
> > -	unsigned int page_shift;
> > +	struct pci_epc_mem_window *window = NULL;
> >  	size_t page_size;
> > -	int bitmap_size;
> > -	int pages;
> >  	int ret;
> >  	int i;
> >  
> > -	epc->num_windows = 0;
> > -
> >  	if (!windows || !num_windows)
> >  		return -EINVAL;
> >  
> > @@ -70,45 +45,51 @@ int pci_epc_multi_mem_init(struct pci_epc *epc,
> >  		page_size = windows[i].page_size;
> >  		if (page_size < PAGE_SIZE)
> >  			page_size = PAGE_SIZE;
> > -		page_shift = ilog2(page_size);
> > -		pages = windows[i].size >> page_shift;
> > -		bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);
> >  
> > -		mem = kzalloc(sizeof(*mem), GFP_KERNEL);
> > -		if (!mem) {
> > +		windows[i].pool = gen_pool_create(ilog2(page_size), -1);
> 
> I think it is not good to modify caller's memory. This funciton suppose
> pass down read-only information. And set to epc->windows[i]. I think it'd
> better to use epc->windows[i].pool/windows.
> 
> > +		if (!windows[i].pool) {
> >  			ret = -ENOMEM;
> > -			i--;
> > -			goto err_mem;
> > +			goto err_free_mem;
> > +		}
> > +
> > +		gen_pool_set_algo(windows[i].pool, gen_pool_first_fit_order_align,
> > +				  NULL);
> > +
> > +		windows[i].virt_base = ioremap(windows[i].phys_base, windows[i].size);
> > +		ret = gen_pool_add_virt(windows[i].pool, (unsigned long)windows[i].virt_base,
> > +					windows[i].phys_base, windows[i].size, -1);
> > +		if (ret) {
> > +			iounmap(windows[i].virt_base);
> > +			gen_pool_destroy(epc->windows[i]->pool);
> 
> I think move all free to err path will be easy to understand.
> 
> > +			goto err_free_mem;
> >  		}
> >  
> > -		bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> > -		if (!bitmap) {
> > +		window = kzalloc(sizeof(*window), GFP_KERNEL);
> 
> According to below code                                                    
>                                                                            
>         epc->windows = kcalloc(num_windows, sizeof(*epc->windows), GFP_KERNEL);
>         if (!epc->windows)                                                 
>                 return -ENOMEM;                                            
>                                                                            
> epc->windows already allocate whole num_windows * "struct pci_epc_mem_window".
> I think you can direct use 'window = epc->windows + i', so needn't alloc      
> additional memory for epc->windows[i].

I just realize struct pci_epc_mem_window **windows in epc. But my comment
should be valid also. pci_epc_mem_window *windows should be enough. Needn't
two level pointer.

> 
> 
> > +		if (!window) {
> >  			ret = -ENOMEM;
> > -			kfree(mem);
> > -			i--;
> > -			goto err_mem;
> > +			iounmap(windows[i].virt_base);
> > +			gen_pool_destroy(epc->windows[i]->pool);
> > +			goto err_free_mem;
> >  		}
> >  
> > -		mem->window.phys_base = windows[i].phys_base;
> > -		mem->window.size = windows[i].size;
> > -		mem->window.page_size = page_size;
> > -		mem->bitmap = bitmap;
> > -		mem->pages = pages;
> > -		mutex_init(&mem->lock);
> > -		epc->windows[i] = mem;
> > +		window->phys_base = windows[i].phys_base;
> > +		window->size = windows[i].size;
> > +		window->page_size = page_size;
> > +		window->pool = windows[i].pool;
> > +		epc->windows[i] = window;
> >  	}
> >  
> > -	epc->mem = epc->windows[0];
> >  	epc->num_windows = num_windows;
> >  
> >  	return 0;
> >  
> > -err_mem:
> > -	for (; i >= 0; i--) {
> > -		mem = epc->windows[i];
> > -		kfree(mem->bitmap);
> > -		kfree(mem);
> > +err_free_mem:
> > +	for (--i; i >= 0; i--) {
> > +		iounmap(windows[i].virt_base);
> > +		gen_pool_destroy(epc->windows[i]->pool);
> > +		kfree(epc->windows[i]);
> >  	}
> > +
> >  	kfree(epc->windows);
> >  
> >  	return ret;
> > @@ -128,14 +109,15 @@ EXPORT_SYMBOL_GPL(pci_epc_multi_mem_init);
> >  int pci_epc_mem_init(struct pci_epc *epc, phys_addr_t base,
> >  		     size_t size, size_t page_size)
> >  {
> > -	struct pci_epc_mem_window mem_window;
> > +	struct pci_epc_mem_window window;
> >  
> > -	mem_window.phys_base = base;
> > -	mem_window.size = size;
> > -	mem_window.page_size = page_size;
> > +	window.phys_base = base;
> > +	window.size = size;
> > +	window.page_size = page_size;
> >  
> > -	return pci_epc_multi_mem_init(epc, &mem_window, 1);
> > +	return pci_epc_multi_mem_init(epc, &window, 1);
> >  }
> > +
> 
> Remove extra empty line change
> 
> >  EXPORT_SYMBOL_GPL(pci_epc_mem_init);
> >  
> >  /**
> > @@ -147,21 +129,20 @@ EXPORT_SYMBOL_GPL(pci_epc_mem_init);
> >   */
> >  void pci_epc_mem_exit(struct pci_epc *epc)
> >  {
> > -	struct pci_epc_mem *mem;
> >  	int i;
> >  
> >  	if (!epc->num_windows)
> >  		return;
> >  
> >  	for (i = 0; i < epc->num_windows; i++) {
> > -		mem = epc->windows[i];
> > -		kfree(mem->bitmap);
> > -		kfree(mem);
> > +		iounmap(epc->windows[i]->virt_base);
> > +		gen_pool_destroy(epc->windows[i]->pool);
> > +		kfree(epc->windows[i]);
> >  	}
> > +
> >  	kfree(epc->windows);
> >  
> >  	epc->windows = NULL;
> > -	epc->mem = NULL;
> >  	epc->num_windows = 0;
> >  }
> >  EXPORT_SYMBOL_GPL(pci_epc_mem_exit);
> > @@ -178,55 +159,42 @@ EXPORT_SYMBOL_GPL(pci_epc_mem_exit);
> >  void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
> >  				     phys_addr_t *phys_addr, size_t size)
> >  {
> > +	struct pci_epc_mem_window *window;
> >  	void __iomem *virt_addr = NULL;
> > -	struct pci_epc_mem *mem;
> > -	unsigned int page_shift;
> > +	struct gen_pool *genpool;
> >  	size_t align_size;
> > -	int pageno;
> > -	int order;
> >  	int i;
> >  
> >  	for (i = 0; i < epc->num_windows; i++) {
> > -		mem = epc->windows[i];
> > -		mutex_lock(&mem->lock);
> > -		align_size = ALIGN(size, mem->window.page_size);
> > -		order = pci_epc_mem_get_order(mem, align_size);
> > -
> > -		pageno = bitmap_find_free_region(mem->bitmap, mem->pages,
> > -						 order);
> > -		if (pageno >= 0) {
> > -			page_shift = ilog2(mem->window.page_size);
> > -			*phys_addr = mem->window.phys_base +
> > -				((phys_addr_t)pageno << page_shift);
> > -			virt_addr = ioremap(*phys_addr, align_size);
> > -			if (!virt_addr) {
> > -				bitmap_release_region(mem->bitmap,
> > -						      pageno, order);
> > -				mutex_unlock(&mem->lock);
> > -				continue;
> > -			}
> > -			mutex_unlock(&mem->lock);
> > -			return virt_addr;
> > -		}
> > -		mutex_unlock(&mem->lock);
> > +		window = epc->windows[i];
> > +		genpool = window->pool;
> > +		align_size = ALIGN(size, window->page_size);
> > +
> > +		virt_addr = (void __iomem *)gen_pool_alloc(genpool, align_size);
> > +		if (!virt_addr)
> > +			continue;
> > +
> > +		*phys_addr = gen_pool_virt_to_phys(genpool, (unsigned long)virt_addr);
> > +
> > +		break;
> >  	}
> >  
> >  	return virt_addr;
> >  }
> >  EXPORT_SYMBOL_GPL(pci_epc_mem_alloc_addr);
> >  
> > -static struct pci_epc_mem *pci_epc_get_matching_window(struct pci_epc *epc,
> > +static struct pci_epc_mem_window *pci_epc_get_matching_window(struct pci_epc *epc,
> >  						       phys_addr_t phys_addr)
> >  {
> > -	struct pci_epc_mem *mem;
> > +	struct pci_epc_mem_window *window;
> >  	int i;
> >  
> >  	for (i = 0; i < epc->num_windows; i++) {
> > -		mem = epc->windows[i];
> > +		window = epc->windows[i];
> >  
> > -		if (phys_addr >= mem->window.phys_base &&
> > -		    phys_addr < (mem->window.phys_base + mem->window.size))
> > -			return mem;
> > +		if (phys_addr >= window->phys_base &&
> > +		    phys_addr < (window->phys_base + window->size))
> > +			return window;
> >  	}
> >  
> >  	return NULL;
> > @@ -244,27 +212,15 @@ static struct pci_epc_mem *pci_epc_get_matching_window(struct pci_epc *epc,
> >  void pci_epc_mem_free_addr(struct pci_epc *epc, phys_addr_t phys_addr,
> >  			   void __iomem *virt_addr, size_t size)
> >  {
> > -	struct pci_epc_mem *mem;
> > -	unsigned int page_shift;
> > -	size_t page_size;
> > -	int pageno;
> > -	int order;
> > +	struct pci_epc_mem_window *window;
> >  
> > -	mem = pci_epc_get_matching_window(epc, phys_addr);
> > -	if (!mem) {
> > +	window = pci_epc_get_matching_window(epc, phys_addr);
> > +	if (!window) {
> >  		pr_err("failed to get matching window\n");
> >  		return;
> >  	}
> >  
> > -	page_size = mem->window.page_size;
> > -	page_shift = ilog2(page_size);
> > -	iounmap(virt_addr);
> > -	pageno = (phys_addr - mem->window.phys_base) >> page_shift;
> > -	size = ALIGN(size, page_size);
> > -	order = pci_epc_mem_get_order(mem, size);
> > -	mutex_lock(&mem->lock);
> > -	bitmap_release_region(mem->bitmap, pageno, order);
> > -	mutex_unlock(&mem->lock);
> > +	gen_pool_free(window->pool, (unsigned long)virt_addr, size);
> >  }
> >  EXPORT_SYMBOL_GPL(pci_epc_mem_free_addr);
> >  
> > diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> > index 40ea18f5aa02..37ea96ed3432 100644
> > --- a/include/linux/pci-epc.h
> > +++ b/include/linux/pci-epc.h
> > @@ -87,30 +87,19 @@ struct pci_epc_ops {
> >  /**
> >   * struct pci_epc_mem_window - address window of the endpoint controller
> >   * @phys_base: physical base address of the PCI address window
> > + * @virt_base: virtual base address of the PCI address window
> > + * @pool: memory pool descriptor
> >   * @size: the size of the PCI address window
> >   * @page_size: size of each page
> >   */
> >  struct pci_epc_mem_window {
> >  	phys_addr_t	phys_base;
> > +	void __iomem	*virt_base;
> > +	struct gen_pool *pool;
> >  	size_t		size;
> >  	size_t		page_size;
> >  };
> >  
> > -/**
> > - * struct pci_epc_mem - address space of the endpoint controller
> > - * @window: address window of the endpoint controller
> > - * @bitmap: bitmap to manage the PCI address space
> > - * @pages: number of bits representing the address region
> > - * @lock: mutex to protect bitmap
> > - */
> > -struct pci_epc_mem {
> > -	struct pci_epc_mem_window window;
> > -	unsigned long	*bitmap;
> > -	int		pages;
> > -	/* mutex to protect against concurrent access for memory allocation*/
> > -	struct mutex	lock;
> > -};
> > -
> >  /**
> >   * struct pci_epc - represents the PCI EPC device
> >   * @dev: PCI EPC device
> > @@ -118,9 +107,6 @@ struct pci_epc_mem {
> >   * @list_lock: Mutex for protecting pci_epf list
> >   * @ops: function pointers for performing endpoint operations
> >   * @windows: array of address space of the endpoint controller
> > - * @mem: first window of the endpoint controller, which corresponds to
> > - *       default address space of the endpoint controller supporting
> > - *       single window.
> >   * @num_windows: number of windows supported by device
> >   * @max_functions: max number of functions that can be configured in this EPC
> >   * @max_vfs: Array indicating the maximum number of virtual functions that can
> > @@ -134,8 +120,7 @@ struct pci_epc {
> >  	struct list_head		pci_epf;
> >  	struct mutex			list_lock;
> >  	const struct pci_epc_ops	*ops;
> > -	struct pci_epc_mem		**windows;
> > -	struct pci_epc_mem		*mem;
> > +	struct pci_epc_mem_window	**windows;
> >  	unsigned int			num_windows;
> >  	u8				max_functions;
> >  	u8				*max_vfs;
> > 
> > ---
> > base-commit: 256833a66670ff28b7c1bddbd17973619e5281fd
> > change-id: 20240317-pci-ep-genalloc-fa89f5e487e3
> > 
> > Best regards,
> > -- 
> > Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > 

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