Re: [PATCH v2] x86/amd_nb: unexport amd_cache_northbridges()

["Chatradhi, Naveen Krishna" <nchatrad@amd.com>]

Hi Boris,

On 3/25/2022 12:40 AM, Borislav Petkov wrote:
> [CAUTION: External Email]
>
> On Thu, Mar 24, 2022 at 05:57:29PM +0530, Naveen Krishna Chatradhi wrote:
>> From: Muralidhara M K <muralimk@amd.com>
>>
>> amd_cache_northbridges() is exported by amd_nb.c and is used by
>> amd64-agp.c and amd64_edac.c modules.
>>
>> init_amd_nbs() already calls amd_cache_northbridges() unconditionally,
>> during fs_initcall() phase, which happens before the device_initcall().
> No, that's not even trying. I went and did your work for you. Please
> try harder in the future to really really explain why you're doing what
> you're doing so that a reader of your commit message can easily follow
> your logic and not have to do research just to figure out why your
> change is ok.

Understood, will try and explain better for future patches.

Thank you

>
> ---
>  From f5e82ad4c749afb63cdebba6729452e516bc1fa9 Mon Sep 17 00:00:00 2001
> From: Muralidhara M K <muralimk@amd.com>
> Date: Thu, 24 Mar 2022 17:57:29 +0530
> Subject: [PATCH] x86/amd_nb: Unexport amd_cache_northbridges()
>
> amd_cache_northbridges() is exported by amd_nb.c and is called by
> amd64-agp.c and amd64_edac.c modules at module_init() time so that NB
> descriptors are properly cached before those drivers can use them.
>
> However, the init_amd_nbs() initcall already does call
> amd_cache_northbridges() unconditionally and thus makes sure the NB
> descriptors are enumerated.
>
> That initcall is a fs_initcall type which is on the 5th group (starting
> from 0) of initcalls that gets run in increasing numerical order by the
> init code.
>
> The module_init() call is turned into an __initcall() in the MODULE=n
> case and those are device-level initcalls, i.e., group 6.
>
> Therefore, the northbridges caching is already finished by the time
> module initialization starts and thus the correct initialization order
> is retained.
>
> Unexport amd_cache_northbridges(), update dependent modules to
> call amd_nb_num() instead. While at it, simplify the checks in
> amd_cache_northbridges().
>
>    [ bp: Heavily massage and *actually* explain why the change is ok. ]
>
> Signed-off-by: Muralidhara M K <muralimk@amd.com>
> Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr%2F20220324122729.221765-1-nchatrad%40amd.com&amp;data=04%7C01%7CNaveenKrishna.Chatradhi%40amd.com%7Cad77d5aa72554663e79d08da0dca506b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637837460434170931%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=MsZNFF0%2F5x%2BJkuOPtL%2BNFZRxtBe548sVkEbyHOUcTcQ%3D&amp;reserved=0
> ---
>   arch/x86/include/asm/amd_nb.h | 1 -
>   arch/x86/kernel/amd_nb.c      | 7 +++----
>   drivers/char/agp/amd64-agp.c  | 2 +-
>   drivers/edac/amd64_edac.c     | 2 +-
>   4 files changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/amd_nb.h b/arch/x86/include/asm/amd_nb.h
> index 00d1a400b7a1..ed0eaf65c437 100644
> --- a/arch/x86/include/asm/amd_nb.h
> +++ b/arch/x86/include/asm/amd_nb.h
> @@ -16,7 +16,6 @@ extern const struct amd_nb_bus_dev_range amd_nb_bus_dev_ranges[];
>
>   extern bool early_is_amd_nb(u32 value);
>   extern struct resource *amd_get_mmconfig_range(struct resource *res);
> -extern int amd_cache_northbridges(void);
>   extern void amd_flush_garts(void);
>   extern int amd_numa_init(void);
>   extern int amd_get_subcaches(int);
> diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
> index 020c906f7934..190e0f763375 100644
> --- a/arch/x86/kernel/amd_nb.c
> +++ b/arch/x86/kernel/amd_nb.c
> @@ -188,7 +188,7 @@ int amd_smn_write(u16 node, u32 address, u32 value)
>   EXPORT_SYMBOL_GPL(amd_smn_write);
>
>
> -int amd_cache_northbridges(void)
> +static int amd_cache_northbridges(void)
>   {
>          const struct pci_device_id *misc_ids = amd_nb_misc_ids;
>          const struct pci_device_id *link_ids = amd_nb_link_ids;
> @@ -210,14 +210,14 @@ int amd_cache_northbridges(void)
>          }
>
>          misc = NULL;
> -       while ((misc = next_northbridge(misc, misc_ids)) != NULL)
> +       while ((misc = next_northbridge(misc, misc_ids)))
>                  misc_count++;
>
>          if (!misc_count)
>                  return -ENODEV;
>
>          root = NULL;
> -       while ((root = next_northbridge(root, root_ids)) != NULL)
> +       while ((root = next_northbridge(root, root_ids)))
>                  root_count++;
>
>          if (root_count) {
> @@ -290,7 +290,6 @@ int amd_cache_northbridges(void)
>
>          return 0;
>   }
> -EXPORT_SYMBOL_GPL(amd_cache_northbridges);
>
>   /*
>    * Ignores subdevice/subvendor but as far as I can figure out
> diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c
> index dc78a4fb879e..84a4aa9312cf 100644
> --- a/drivers/char/agp/amd64-agp.c
> +++ b/drivers/char/agp/amd64-agp.c
> @@ -327,7 +327,7 @@ static int cache_nbs(struct pci_dev *pdev, u32 cap_ptr)
>   {
>          int i;
>
> -       if (amd_cache_northbridges() < 0)
> +       if (!amd_nb_num())
>                  return -ENODEV;
>
>          if (!amd_nb_has_feature(AMD_NB_GART))
> diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
> index fba609ada0e6..af2c578f8ab3 100644
> --- a/drivers/edac/amd64_edac.c
> +++ b/drivers/edac/amd64_edac.c
> @@ -4269,7 +4269,7 @@ static int __init amd64_edac_init(void)
>          if (!x86_match_cpu(amd64_cpuids))
>                  return -ENODEV;
>
> -       if (amd_cache_northbridges() < 0)
> +       if (!amd_nb_num())
>                  return -ENODEV;
>
>          opstate_init();
> --
> 2.35.1
>
> --
> Regards/Gruss,
>      Boris.
>
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