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Date: Tue, 19 Mar 2024 13:01:03 -0400
From: Frank Li <Frank.li@nxp.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Jingoo Han <jingoohan1@gmail.com>,
	Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Rob Herring <robh@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
	Kishon Vijay Abraham I <kishon@kernel.org>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PCI: endpoint: Migrate to Genalloc framework for
 outbound window memory allocation
Message-ID: <ZfnEz9w6ICZXFZeb@lizhi-Precision-Tower-5810>
References: <20240317-pci-ep-genalloc-v1-1-70fe52a3b9be@linaro.org>
 <Zfm0Ws/Zg1W2UVZt@lizhi-Precision-Tower-5810>
 <20240319162829.GC3297@thinkpad>
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On Tue, Mar 19, 2024 at 09:58:29PM +0530, Manivannan Sadhasivam wrote:
> 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@linaro.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@ti.com>
> > > + *
> > > + * Copyright (C) 2024 Linaro Ltd.
> > > + * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.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.
> > 
> 
> What do you mean by modifying caller's memory? Here, the memory for epc->windows
> is being allocated and the pool is created for each window.

windows[i].pool = gen_pool_create(ilog2(page_size), -1)

'windows' pass down from argument pci_epc_multi_mem_init(
.struct pci_epc_mem_window *windows, )
			     ^^^^^^^
windows[i].pool = gen_pool_create() actually change the caller's stack
memory.

> 
> > > +		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.
> > 
> 
> It is not straightforward. First we need to free the memory for current
> iteration and then all previous iterations, that too from different places.
> Moving the code to free current iteration to the error label will look messy.

All from current iteration.

err_free_mem:
   iounmap(windows[i].virt_base);
   if (epc->windows[i]->pool)
	gen_pool_destroy(epc->windows[i]->pool)

> 
> > > +			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].
> > 
> 
> First we are allocating the memory for 'struct pci_epc_mem_window' _pointers_ in
> epc->windows. Then we need to allocate memory for each pointer in epc->windows
> to actually store data. Otherwise, we will be referencing the nulll pointer.

I think two layer pointer is totally unecessary.
You can use one layer pointer 'struct pci_epc_mem_window       *windows;'

Code logic will become simple. 

Frank

> 
> - Mani
> 
> > 
> > > +		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@linaro.org>
> > > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்