Re: [PATCH v2 1/2] PCI: MCFG: Consolidate the separate PCI MCFG table entry list

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Fri, Oct 08, 2021 at 04:31:43PM -0500, Bjorn Helgaas wrote:
> [+cc Jayachandran, Tomasz; not sure if they're still around, but just
> in case they have a comment on any reasons for keeping the
> pci_mcfg_list list separate.]
> 
> On Fri, Oct 08, 2021 at 04:40:12PM +0800, Xuesong Chen wrote:
> > The PCI MCFG entry list is discrete on x86 and other architectures like
> > arm64 in current implementation, this list variable can be consolidated
> > for unnecessary duplication and other purposes, for example, we can remove
> > some of the 'arch' specific codes in the APEI/EINJ module and re-implement
> > it in a more common arch-agnostic way.
> 
> This commit log could be more explicit about what's going on here.
> 
> From deciphering the patch, I think it takes advantage of the fact
> that struct pci_mmcfg_region and struct mcfg_entry contain basically
> the same information, but pci_mmcfg_region contains a little extra
> information (a struct resource, a virtual address, and a name).
> 
> To reduce the redundancy, it:
> 
>   - Moves the "struct pci_mmcfg_region" definition from
>     arch/x86/include/asm/pci_x86.h to include/linux/pci.h, where it
>     can be shared across arches.
> 
>   - Moves pci_mmcfg_list (a list of pci_mmcfg_region structs) from
>     arch/x86/pci/mmconfig-shared.c to drivers/pci/pci.c, where it can
>     be shared across arches.

This is a bit ugly, especially the resulting ifdef CONFIG_PCI in
patch 2:

https://lore.kernel.org/linux-acpi/YWAEG7fyFC+lhwd+@Dennis-MBP.local

I'd rather make apei_filter_mcfg_addr() conditional, on what, that's
the question.

#ifdef CONFIG_FOO
static int apei_filter_mcfg_addr()
{
...
}
#else
static inline int apei_filter_mcfg_addr() { return 0; }
#endif

>   - On x86 (which does not enable CONFIG_ACPI_MCFG), pci_mmcfg_list is
>     built in arch/x86/pci/mmconfig-shared.c as before.
> 
>   - Removes the "struct mcfg_entry" from drivers/acpi/pci_mcfg.c.
> 
>   - Replaces pci_mcfg_list (previously a list of mcfg_entry structs)
>     in drivers/acpi/pci_mcfg.c with the newly-shared pci_mmcfg_list (a
>     list of pci_mmcfg_region structs).
> 
>   - On ARM64 (which does enable CONFIG_ACPI_MCFG), pci_mmcfg_list is
>     built in drivers/acpi/pci_mcfg.c.
> 
> Does that sound about right?

Yes it does. Another option would consist in doing all the MCFG parsing
(anew) in APEI code to build a temporary list that is discarded as soon
as the resource filtering took place - maybe it is something worth
thinking about (but do we really need more MCFG parsing code ?).

Lorenzo

> > Signed-off-by: Xuesong Chen <xuesong.chen@linux.alibaba.com>
> > ---
> >  arch/x86/include/asm/pci_x86.h | 17 +----------------
> >  arch/x86/pci/mmconfig-shared.c |  2 --
> >  drivers/acpi/pci_mcfg.c        | 34 +++++++++++++---------------------
> >  drivers/pci/pci.c              |  2 ++
> >  include/linux/pci.h            | 17 +++++++++++++++++
> >  5 files changed, 33 insertions(+), 39 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
> > index 490411d..1f4257c 100644
> > --- a/arch/x86/include/asm/pci_x86.h
> > +++ b/arch/x86/include/asm/pci_x86.h
> > @@ -146,20 +146,7 @@ static inline int  __init pci_acpi_init(void)
> >  extern void pcibios_fixup_irqs(void);
> >  
> >  /* pci-mmconfig.c */
> > -
> > -/* "PCI MMCONFIG %04x [bus %02x-%02x]" */
> > -#define PCI_MMCFG_RESOURCE_NAME_LEN (22 + 4 + 2 + 2)
> > -
> > -struct pci_mmcfg_region {
> > -	struct list_head list;
> > -	struct resource res;
> > -	u64 address;
> > -	char __iomem *virt;
> > -	u16 segment;
> > -	u8 start_bus;
> > -	u8 end_bus;
> > -	char name[PCI_MMCFG_RESOURCE_NAME_LEN];
> > -};
> > +struct pci_mmcfg_region;
> >  
> >  extern int __init pci_mmcfg_arch_init(void);
> >  extern void __init pci_mmcfg_arch_free(void);
> > @@ -174,8 +161,6 @@ extern struct pci_mmcfg_region *__init pci_mmconfig_add(int segment, int start,
> >  
> >  extern struct list_head pci_mmcfg_list;
> >  
> > -#define PCI_MMCFG_BUS_OFFSET(bus)      ((bus) << 20)
> > -
> >  /*
> >   * On AMD Fam10h CPUs, all PCI MMIO configuration space accesses must use
> >   * %eax.  No other source or target registers may be used.  The following
> > diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
> > index 758cbfe..0b961fe6 100644
> > --- a/arch/x86/pci/mmconfig-shared.c
> > +++ b/arch/x86/pci/mmconfig-shared.c
> > @@ -31,8 +31,6 @@
> >  static DEFINE_MUTEX(pci_mmcfg_lock);
> >  #define pci_mmcfg_lock_held() lock_is_held(&(pci_mmcfg_lock).dep_map)
> >  
> > -LIST_HEAD(pci_mmcfg_list);
> > -
> >  static void __init pci_mmconfig_remove(struct pci_mmcfg_region *cfg)
> >  {
> >  	if (cfg->res.parent)
> > diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
> > index 53cab97..d9506b0 100644
> > --- a/drivers/acpi/pci_mcfg.c
> > +++ b/drivers/acpi/pci_mcfg.c
> > @@ -13,14 +13,7 @@
> >  #include <linux/pci-acpi.h>
> >  #include <linux/pci-ecam.h>
> >  
> > -/* Structure to hold entries from the MCFG table */
> > -struct mcfg_entry {
> > -	struct list_head	list;
> > -	phys_addr_t		addr;
> > -	u16			segment;
> > -	u8			bus_start;
> > -	u8			bus_end;
> > -};
> > +extern struct list_head pci_mmcfg_list;
> >  
> >  #ifdef CONFIG_PCI_QUIRKS
> >  struct mcfg_fixup {
> > @@ -214,16 +207,13 @@ static void pci_mcfg_apply_quirks(struct acpi_pci_root *root,
> >  #endif
> >  }
> >  
> > -/* List to save MCFG entries */
> > -static LIST_HEAD(pci_mcfg_list);
> > -
> >  int pci_mcfg_lookup(struct acpi_pci_root *root, struct resource *cfgres,
> >  		    const struct pci_ecam_ops **ecam_ops)
> >  {
> >  	const struct pci_ecam_ops *ops = &pci_generic_ecam_ops;
> >  	struct resource *bus_res = &root->secondary;
> >  	u16 seg = root->segment;
> > -	struct mcfg_entry *e;
> > +	struct pci_mmcfg_region *e;
> >  	struct resource res;
> >  
> >  	/* Use address from _CBA if present, otherwise lookup MCFG */
> > @@ -233,10 +223,10 @@ int pci_mcfg_lookup(struct acpi_pci_root *root, struct resource *cfgres,
> >  	/*
> >  	 * We expect the range in bus_res in the coverage of MCFG bus range.
> >  	 */
> > -	list_for_each_entry(e, &pci_mcfg_list, list) {
> > -		if (e->segment == seg && e->bus_start <= bus_res->start &&
> > -		    e->bus_end >= bus_res->end) {
> > -			root->mcfg_addr = e->addr;
> > +	list_for_each_entry(e, &pci_mmcfg_list, list) {
> > +		if (e->segment == seg && e->start_bus <= bus_res->start &&
> > +		    e->end_bus >= bus_res->end) {
> > +			root->mcfg_addr = e->address;
> >  		}
> >  
> >  	}
> > @@ -268,7 +258,7 @@ static __init int pci_mcfg_parse(struct acpi_table_header *header)
> >  {
> >  	struct acpi_table_mcfg *mcfg;
> >  	struct acpi_mcfg_allocation *mptr;
> > -	struct mcfg_entry *e, *arr;
> > +	struct pci_mmcfg_region *e, *arr;
> >  	int i, n;
> >  
> >  	if (header->length < sizeof(struct acpi_table_mcfg))
> > @@ -285,10 +275,12 @@ static __init int pci_mcfg_parse(struct acpi_table_header *header)
> >  
> >  	for (i = 0, e = arr; i < n; i++, mptr++, e++) {
> >  		e->segment = mptr->pci_segment;
> > -		e->addr =  mptr->address;
> > -		e->bus_start = mptr->start_bus_number;
> > -		e->bus_end = mptr->end_bus_number;
> > -		list_add(&e->list, &pci_mcfg_list);
> > +		e->address =  mptr->address;
> > +		e->start_bus = mptr->start_bus_number;
> > +		e->end_bus = mptr->end_bus_number;
> > +		e->res.start = e->address + PCI_MMCFG_BUS_OFFSET(e->start_bus);
> > +		e->res.end = e->address + PCI_MMCFG_BUS_OFFSET(e->end_bus + 1) - 1;
> > +		list_add(&e->list, &pci_mmcfg_list);
> >  	}
> >  
> >  #ifdef CONFIG_PCI_QUIRKS
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index ce2ab62..899004e 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -47,6 +47,8 @@
> >  int pci_pci_problems;
> >  EXPORT_SYMBOL(pci_pci_problems);
> >  
> > +LIST_HEAD(pci_mmcfg_list);
> > +
> >  unsigned int pci_pm_d3hot_delay;
> >  
> >  static void pci_pme_list_scan(struct work_struct *work);
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index cd8aa6f..71e4c06 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -55,6 +55,23 @@
> >  #define PCI_RESET_PROBE		true
> >  #define PCI_RESET_DO_RESET	false
> >  
> > +#define PCI_MMCFG_BUS_OFFSET(bus)      ((bus) << 20)
> > +
> > +/* "PCI MMCONFIG %04x [bus %02x-%02x]" */
> > +#define PCI_MMCFG_RESOURCE_NAME_LEN (22 + 4 + 2 + 2)
> > +
> > +/* pci mcfg region */
> > +struct pci_mmcfg_region {
> > +	struct list_head list;
> > +	struct resource res;
> > +	u64 address;
> > +	char __iomem *virt;
> > +	u16 segment;
> > +	u8 start_bus;
> > +	u8 end_bus;
> > +	char name[PCI_MMCFG_RESOURCE_NAME_LEN];
> > +};
> > +
> >  /*
> >   * The PCI interface treats multi-function devices as independent
> >   * devices.  The slot/function address of each device is encoded
> > -- 
> > 1.8.3.1
> > 

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