Re: [PATCH v2.2] x86/amd_node, platform/x86/amd/hsmp: Have HSMP use SMN through AMD_NODE

[Yazen Ghannam <yazen.ghannam@amd.com>]

On Tue, Dec 24, 2024 at 06:44:17AM +0530, Suma Hegde wrote:
> Hi Yazen,
> 
> 
> On 12/17/2024 12:03 AM, Yazen Ghannam wrote:
> > On Sat, Dec 14, 2024 at 11:05:07AM +0100, Borislav Petkov wrote:
> > > On Fri, Dec 13, 2024 at 03:22:06PM +0000, Yazen Ghannam wrote:
> > > > The HSMP interface is just an SMN interface with different offsets.
> > > > 
> > > > Define an HSMP wrapper in the SMN code and have the HSMP platform driver
> > > > use that rather than a local solution.
> > > > 
> > > > Also, remove the "root" member from AMD_NB, since there are no more
> > > > users of it.
> > > > 
> > > > Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> > > > ---
> > > > 
> > > > Notes:
> > > >      Link:
> > > >      https://lore.kernel.org/20241212172711.1944927-1-yazen.ghannam@amd.com
> > > >      v2.1-v2.2:
> > > >      * Include <linux/build_bug.h> for static_assert()
> > > >      v2->v2.1:
> > > >      * Include static_assert() and comment for sysfs attributes.
> > > >      v1->v2:
> > > >      * Rebase on recent HSMP rework.
> > > > 
> > > >   arch/x86/include/asm/amd_nb.h         |  1 -
> > > >   arch/x86/include/asm/amd_node.h       |  3 +++
> > > >   arch/x86/kernel/amd_nb.c              |  1 -
> > > >   arch/x86/kernel/amd_node.c            |  9 +++++++
> > > >   drivers/platform/x86/amd/hsmp/Kconfig |  2 +-
> > > >   drivers/platform/x86/amd/hsmp/acpi.c  |  7 +++---
> > > >   drivers/platform/x86/amd/hsmp/hsmp.c  |  1 -
> > > >   drivers/platform/x86/amd/hsmp/hsmp.h  |  3 ---
> > > >   drivers/platform/x86/amd/hsmp/plat.c  | 36 +++++++++------------------
> > > >   9 files changed, 29 insertions(+), 34 deletions(-)
> > > ld: drivers/platform/x86/amd/hsmp/plat.o: in function `amd_hsmp_pci_rdwr':
> > > /home/amd/kernel/linux/drivers/platform/x86/amd/hsmp/plat.c:44: undefined reference to `amd_smn_hsmp_rdwr'
> > > make[2]: *** [scripts/Makefile.vmlinux:77: vmlinux] Error 1
> > > make[1]: *** [/home/amd/bpetkov/kernel/linux/Makefile:1225: vmlinux] Error 2
> > > make[1]: *** Waiting for unfinished jobs....
> > > make: *** [Makefile:251: __sub-make] Error 2
> > > 
> > > Config attached.
> > > 
> > I think the fix is this:
> > 
> > diff --git a/drivers/platform/x86/amd/hsmp/Kconfig b/drivers/platform/x86/amd/hsmp/Kconfig
> > index d6f7a62d55b5..fc90ef11a8ad 100644
> > --- a/drivers/platform/x86/amd/hsmp/Kconfig
> > +++ b/drivers/platform/x86/amd/hsmp/Kconfig
> > @@ -7,7 +7,6 @@ config AMD_HSMP
> >   	tristate
> >   menu "AMD HSMP Driver"
> > -	depends on AMD_NODE || COMPILE_TEST
> >   config AMD_HSMP_ACPI
> >   	tristate "AMD HSMP ACPI device driver"
> > @@ -29,6 +28,7 @@ config AMD_HSMP_ACPI
> >   config AMD_HSMP_PLAT
> >   	tristate "AMD HSMP platform device driver"
> > +	depends on AMD_NODE
> >   	select AMD_HSMP
> >   	help
> >   	  Host System Management Port (HSMP) interface is a mailbox interface
> > 
> > With all the recent rework, only AMD_HSMP_PLAT has a hard dependency on
> > AMD_NODE due to needing the SMN register access interface.
> > 
> > Various HSMP files still pull in <asm/amd_node.h>, but they just need
> > defines and an inline function.
> > 
> > It seems COMPILE_TEST is not needed, since this change allows
> > AMD_HSMP_ACPI to build without AMD_NODE which seems like the intent.
> 
> COMPILE_TEST was added to provide build coverage to HSMP based on Ilpo's
> suggestion.
> 
> We can probably add #ifdef CONFIG_AMD_NODE and #else as below to fix this
> instead of removing COMPILE_TEST?
> 
> #ifdef CONFIG_AMD_NODE
> /* Should only be used by the HSMP driver. */
> int __must_check amd_smn_hsmp_rdwr(u16 node, u32 address, u32 *value, bool
> write);
> #else
> static int amd_smn_hsmp_rdwr(u16 node, u32 address, u32 *value, bool write);
> {
>         return 0;
> }
> 
> #endif
> 
> May be Ilpo can comment more.
> 

Thanks Suma for the feedback.

If the intent is to increase build coverage, then I think AMD_HSMP_ACPI
also needs COMPILE_TEST.

We could do the following in addition to the #ifdef.

---
 drivers/platform/x86/amd/hsmp/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/amd/hsmp/Kconfig b/drivers/platform/x86/amd/hsmp/Kconfig
index d6f7a62d55b5..b60933806eed 100644
--- a/drivers/platform/x86/amd/hsmp/Kconfig
+++ b/drivers/platform/x86/amd/hsmp/Kconfig
@@ -7,11 +7,10 @@ config AMD_HSMP
 	tristate
 
 menu "AMD HSMP Driver"
-	depends on AMD_NODE || COMPILE_TEST
 
 config AMD_HSMP_ACPI
 	tristate "AMD HSMP ACPI device driver"
-	depends on ACPI
+	depends on ACPI || COMPILE_TEST
 	select AMD_HSMP
 	help
 	  Host System Management Port (HSMP) interface is a mailbox interface
@@ -29,6 +28,7 @@ config AMD_HSMP_ACPI
 
 config AMD_HSMP_PLAT
 	tristate "AMD HSMP platform device driver"
+	depends on AMD_NODE || COMPILE_TEST
 	select AMD_HSMP
 	help
 	  Host System Management Port (HSMP) interface is a mailbox interface
-- 

The scope of AMD_NODE is reduced to only what needs it. And each option
can be independently built to increase coverage.

How does this sound?

Thanks,
Yazen