[PATCH] x86/pci: Annotate 'pci_root_ops' with __ro_after_init

[PATCH] x86/pci: Annotate 'pci_root_ops' with __ro_after_init

[Zubin Mithra]

When CONFIG_X86_INTEL_MID is set pci_root_ops is written to inside
intel_mid_pci_init(which is marked __init) and not modified after. This
makes pci_root_ops a suitable candidate for annotating as
__ro_after_init.

Signed-off-by: Zubin Mithra <zsm@chromium.org>
---
 arch/x86/pci/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index d4ec117c1142..204ee80cfa63 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -67,7 +67,7 @@ static int pci_write(struct pci_bus *bus, unsigned int devfn, int where, int siz
 				  devfn, where, size, value);
 }
 
-struct pci_ops pci_root_ops = {
+struct pci_ops pci_root_ops __ro_after_init = {
 	.read = pci_read,
 	.write = pci_write,
 };
-- 
2.19.1.930.g4563a0d9d0-goog

Re: [PATCH] x86/pci: Annotate 'pci_root_ops' with __ro_after_init

[Thomas Gleixner]

On Mon, 5 Nov 2018, Zubin Mithra wrote:

Cc+: Bjorn

> When CONFIG_X86_INTEL_MID is set pci_root_ops is written to inside
> intel_mid_pci_init(which is marked __init) and not modified after. This
> makes pci_root_ops a suitable candidate for annotating as
> __ro_after_init.

This is confusing. What about CONFIG_X86_INTEL_MID=n?

What you want to say is:

 pci_root_ops is only modified from intel_mid_pci_init() which is a init
 function, so it can be made __ro_after_init.

or something like this. Hmm?

Other than the nitpick above:

      Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

> Signed-off-by: Zubin Mithra <zsm@chromium.org>
> ---
>  arch/x86/pci/common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index d4ec117c1142..204ee80cfa63 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -67,7 +67,7 @@ static int pci_write(struct pci_bus *bus, unsigned int devfn, int where, int siz
>  				  devfn, where, size, value);
>  }
>  
> -struct pci_ops pci_root_ops = {
> +struct pci_ops pci_root_ops __ro_after_init = {
>  	.read = pci_read,
>  	.write = pci_write,
>  };
> -- 
> 2.19.1.930.g4563a0d9d0-goog
> 
> 

Re: [PATCH] x86/pci: Annotate 'pci_root_ops' with __ro_after_init

[Christoph Hellwig]

On Mon, Nov 05, 2018 at 12:17:35PM -0800, Zubin Mithra wrote:
> When CONFIG_X86_INTEL_MID is set pci_root_ops is written to inside
> intel_mid_pci_init(which is marked __init) and not modified after. This
> makes pci_root_ops a suitable candidate for annotating as
> __ro_after_init.

Yikes.  pci_root_ops really should be const to start with, and we
should use a separate struct for MID.  Having structures that contain
function pointers not marked const is generally a bad idea to start with.