Re: git: a7e483ee146a - main - vm_phys: Add a sysctl to dump registered fictitious memory ranges

In reply to: Mark Johnston : "git: a7e483ee146a - main - vm_phys: Add a sysctl to dump registered fictitious memory ranges"
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From: A FreeBSD User <freebsd_at_walstatt-de.de>
Date: Sun, 19 Jul 2026 09:48:09 UTC
Am Tage des Herren Sun, 19 Jul 2026 00:37:19 +0000
Mark Johnston <markj@FreeBSD.org> schrieb:

> The branch main has been updated by markj:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=a7e483ee146a93ac89357676fdb9af62ac58b4bc
> 
> commit a7e483ee146a93ac89357676fdb9af62ac58b4bc
> Author:     Mark Johnston <markj@FreeBSD.org>
> AuthorDate: 2026-07-19 00:29:40 +0000
> Commit:     Mark Johnston <markj@FreeBSD.org>
> CommitDate: 2026-07-19 00:29:40 +0000
> 
>     vm_phys: Add a sysctl to dump registered fictitious memory ranges
>     
>     I've wanted this a couple of times in the past.  Save the memattr in
>     the fictitious memory segment structure so that we can report it from
>     the sysctl handler, and add conversion routines for each platform.
>     
>     Reviewed by:    kib
>     MFC after:      2 weeks
>     Differential Revision:  https://reviews.freebsd.org/D58283
> ---
>  sys/amd64/include/vm.h   | 23 +++++++++++++++++++++++
>  sys/arm/include/vm.h     | 19 +++++++++++++++++++
>  sys/arm64/include/vm.h   | 25 +++++++++++++++++++++++--
>  sys/i386/include/vm.h    | 23 +++++++++++++++++++++++
>  sys/powerpc/include/vm.h | 25 +++++++++++++++++++++++++
>  sys/riscv/include/vm.h   | 17 +++++++++++++++++
>  sys/vm/vm_phys.c         | 41 +++++++++++++++++++++++++++++++++++++++++
>  7 files changed, 171 insertions(+), 2 deletions(-)
> 
> diff --git a/sys/amd64/include/vm.h b/sys/amd64/include/vm.h
> index 2e156b1cb1be..7219f8650a9f 100644
> --- a/sys/amd64/include/vm.h
> +++ b/sys/amd64/include/vm.h
> @@ -43,4 +43,27 @@
>  #define	VM_MEMATTR_DEFAULT		VM_MEMATTR_WRITE_BACK
>  #define	VM_MEMATTR_DEVICE		VM_MEMATTR_UNCACHEABLE
>  
> +#ifdef _KERNEL
> +static inline const char *
> +vm_memattr_name(vm_memattr_t memattr)
> +{
> +	switch (memattr) {
> +	case VM_MEMATTR_UNCACHEABLE:
> +		return ("uncacheable");
> +	case VM_MEMATTR_WRITE_COMBINING:
> +		return ("write-combining");
> +	case VM_MEMATTR_WRITE_THROUGH:
> +		return ("write-through");
> +	case VM_MEMATTR_WRITE_PROTECTED:
> +		return ("write-protected");
> +	case VM_MEMATTR_WRITE_BACK:
> +		return ("write-back");
> +	case VM_MEMATTR_WEAK_UNCACHEABLE:
> +		return ("weak-uncacheable");
> +	default:
> +		return (NULL);
> +	}
> +}
> +#endif
> +
>  #endif /* !_MACHINE_VM_H_ */
> diff --git a/sys/arm/include/vm.h b/sys/arm/include/vm.h
> index 697b48689bd8..373f51adec82 100644
> --- a/sys/arm/include/vm.h
> +++ b/sys/arm/include/vm.h
> @@ -41,6 +41,25 @@
>  /* Don't export aliased VM_MEMATTR to userland */
>  #define VM_MEMATTR_WRITE_COMBINING 	VM_MEMATTR_WRITE_THROUGH /* for DRM */
>  #define VM_MEMATTR_WRITE_BACK		VM_MEMATTR_WB_WA	/* for DRM */
> +
> +static inline const char *
> +vm_memattr_name(vm_memattr_t memattr)
> +{
> +	switch (memattr) {
> +	case VM_MEMATTR_WB_WA:
> +		return ("write-back, write-allocate");
> +	case VM_MEMATTR_NOCACHE:
> +		return ("uncacheable");
> +	case VM_MEMATTR_DEVICE:
> +		return ("device");
> +	case VM_MEMATTR_SO:
> +		return ("strongly-ordered");
> +	case VM_MEMATTR_WRITE_THROUGH:
> +		return ("write-through");
> +	default:
> +		return (NULL);
> +	}
> +}
>  #endif
>  
>  #endif /* !_MACHINE_VM_H_ */
> diff --git a/sys/arm64/include/vm.h b/sys/arm64/include/vm.h
> index 4d9f2860f654..87a1839b7dac 100644
> --- a/sys/arm64/include/vm.h
> +++ b/sys/arm64/include/vm.h
> @@ -39,11 +39,32 @@
>  #define	VM_MEMATTR_DEVICE		VM_MEMATTR_DEVICE_nGnRE
>  #define	VM_MEMATTR_DEVICE_NP		VM_MEMATTR_DEVICE_nGnRnE
>  
> +#define	VM_MEMATTR_DEFAULT		VM_MEMATTR_WRITE_BACK
> +
>  #ifdef _KERNEL
>  /* If defined vmstat will try to use both of these in a switch statement */
>  #define	VM_MEMATTR_WRITE_COMBINING	VM_MEMATTR_WRITE_THROUGH
> -#endif
>  
> -#define	VM_MEMATTR_DEFAULT	VM_MEMATTR_WRITE_BACK
> +static inline const char *
> +vm_memattr_name(vm_memattr_t memattr)
> +{
> +	switch (memattr) {
> +	case VM_MEMATTR_DEVICE_nGnRnE:
> +		return ("device-nGnRnE");
> +	case VM_MEMATTR_UNCACHEABLE:
> +		return ("uncacheable");
> +	case VM_MEMATTR_WRITE_BACK:
> +		return ("write-back");
> +	case VM_MEMATTR_WRITE_THROUGH:
> +		return ("write-through");
> +	case VM_MEMATTR_DEVICE_nGnRE:
> +		return ("device-nGnRE");
> +	case VM_MEMATTR_TAGGED:
> +		return ("tagged");
> +	default:
> +		return (NULL);
> +	}
> +}
> +#endif
>  
>  #endif /* !_MACHINE_VM_H_ */
> diff --git a/sys/i386/include/vm.h b/sys/i386/include/vm.h
> index 2e156b1cb1be..7219f8650a9f 100644
> --- a/sys/i386/include/vm.h
> +++ b/sys/i386/include/vm.h
> @@ -43,4 +43,27 @@
>  #define	VM_MEMATTR_DEFAULT		VM_MEMATTR_WRITE_BACK
>  #define	VM_MEMATTR_DEVICE		VM_MEMATTR_UNCACHEABLE
>  
> +#ifdef _KERNEL
> +static inline const char *
> +vm_memattr_name(vm_memattr_t memattr)
> +{
> +	switch (memattr) {
> +	case VM_MEMATTR_UNCACHEABLE:
> +		return ("uncacheable");
> +	case VM_MEMATTR_WRITE_COMBINING:
> +		return ("write-combining");
> +	case VM_MEMATTR_WRITE_THROUGH:
> +		return ("write-through");
> +	case VM_MEMATTR_WRITE_PROTECTED:
> +		return ("write-protected");
> +	case VM_MEMATTR_WRITE_BACK:
> +		return ("write-back");
> +	case VM_MEMATTR_WEAK_UNCACHEABLE:
> +		return ("weak-uncacheable");
> +	default:
> +		return (NULL);
> +	}
> +}
> +#endif
> +
>  #endif /* !_MACHINE_VM_H_ */
> diff --git a/sys/powerpc/include/vm.h b/sys/powerpc/include/vm.h
> index 5c99cda51257..87d0faf44f2e 100644
> --- a/sys/powerpc/include/vm.h
> +++ b/sys/powerpc/include/vm.h
> @@ -42,4 +42,29 @@
>  
>  #define	VM_MEMATTR_DEVICE		VM_MEMATTR_DEFAULT
>  
> +#ifdef _KERNEL
> +static inline const char *
> +vm_memattr_name(vm_memattr_t memattr)
> +{
> +	switch (memattr) {
> +	case VM_MEMATTR_DEFAULT:
> +		return ("default");
> +	case VM_MEMATTR_UNCACHEABLE:
> +		return ("uncacheable");
> +	case VM_MEMATTR_CACHEABLE:
> +		return ("cacheable");
> +	case VM_MEMATTR_WRITE_COMBINING:
> +		return ("write-combining");
> +	case VM_MEMATTR_WRITE_BACK:
> +		return ("write-back");
> +	case VM_MEMATTR_WRITE_THROUGH:
> +		return ("write-through");
> +	case VM_MEMATTR_PREFETCHABLE:
> +		return ("prefetchable");
> +	default:
> +		return (NULL);
> +	}
> +}
> +#endif
> +
>  #endif /* !_MACHINE_VM_H_ */
> diff --git a/sys/riscv/include/vm.h b/sys/riscv/include/vm.h
> index b6c0a7725124..66211fcc2580 100644
> --- a/sys/riscv/include/vm.h
> +++ b/sys/riscv/include/vm.h
> @@ -38,4 +38,21 @@
>  #define	VM_MEMATTR_LAST		VM_MEMATTR_DEVICE
>  #define	VM_MEMATTR_TOTAL	(VM_MEMATTR_LAST + 1)
>  
> +#ifdef _KERNEL
> +static inline const char *
> +vm_memattr_name(vm_memattr_t memattr)
> +{
> +	switch (memattr) {
> +	case VM_MEMATTR_PMA:
> +		return ("write-back");
> +	case VM_MEMATTR_UNCACHEABLE:
> +		return ("uncacheable");
> +	case VM_MEMATTR_DEVICE:
> +		return ("device");
> +	default:
> +		return (NULL);
> +	}
> +}
> +#endif
> +
>  #endif /* !_MACHINE_VM_H_ */
> diff --git a/sys/vm/vm_phys.c b/sys/vm/vm_phys.c
> index 1737020436c6..975754264fee 100644
> --- a/sys/vm/vm_phys.c
> +++ b/sys/vm/vm_phys.c
> @@ -108,6 +108,7 @@ struct vm_phys_fictitious_seg {
>  	vm_paddr_t	start;
>  	vm_paddr_t	end;
>  	vm_page_t	first_page;
> +	vm_memattr_t	memattr;
>  };
>  
>  RB_GENERATE_STATIC(fict_tree, vm_phys_fictitious_seg, node,
> @@ -172,6 +173,12 @@ SYSCTL_OID(_vm, OID_AUTO, phys_segs,
>      sysctl_vm_phys_segs, "A",
>      "Phys Seg Info");
>  
> +static int sysctl_vm_phys_fictitious_segs(SYSCTL_HANDLER_ARGS);
> +SYSCTL_OID(_vm, OID_AUTO, phys_fictitious_segs,
> +    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
> +    sysctl_vm_phys_fictitious_segs, "A",
> +    "Fictitious Phys Seg Info");
> +
>  #ifdef NUMA
>  static int sysctl_vm_phys_locality(SYSCTL_HANDLER_ARGS);
>  SYSCTL_OID(_vm, OID_AUTO, phys_locality,
> @@ -341,6 +348,39 @@ sysctl_vm_phys_segs(SYSCTL_HANDLER_ARGS)
>  	return (error);
>  }
>  
> +static int
> +sysctl_vm_phys_fictitious_segs(SYSCTL_HANDLER_ARGS)
> +{
> +	struct sbuf sbuf;
> +	struct vm_phys_fictitious_seg *seg;
> +	int error;
> +
> +	error = sysctl_wire_old_buffer(req, 0);
> +	if (error != 0)
> +		return (error);
> +	sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
> +	rw_rlock(&vm_phys_fictitious_reg_lock);
> +	RB_FOREACH(seg, fict_tree, &vm_phys_fictitious_tree) {
> +		const char *name;
> +		char buf[8];
> +
> +		sbuf_printf(&sbuf, "\nstart:     %#jx\n",
> +		    (uintmax_t)seg->start);
> +		sbuf_printf(&sbuf, "end:       %#jx\n",
> +		    (uintmax_t)seg->end);
> +		name = vm_memattr_name(seg->memattr);
> +		if (name == NULL) {
> +			(void)snprintf(buf, sizeof(buf), "0x%02x", seg->memattr);
> +			name = buf;
> +		}
> +		sbuf_printf(&sbuf, "attr:      %s\n", name);
> +	}
> +	rw_runlock(&vm_phys_fictitious_reg_lock);
> +	error = sbuf_finish(&sbuf);
> +	sbuf_delete(&sbuf);
> +	return (error);
> +}
> +
>  /*
>   * Return affinity, or -1 if there's no affinity information.
>   */
> @@ -1155,6 +1195,7 @@ alloc:
>  	seg->start = start;
>  	seg->end = end;
>  	seg->first_page = fp;
> +	seg->memattr = memattr;
>  
>  	rw_wlock(&vm_phys_fictitious_reg_lock);
>  	RB_INSERT(fict_tree, &vm_phys_fictitious_tree, seg);
> 
After upgrading sources with this commit, both GPU ports

graphics/drm-66-kmod
graphics/drm-612-kmod

fail with undeclared indentifier NULL as shown below:

[...]

--- drm_client.o ---
In file included from
/usr/obj/usr/src/amd64.amd64/sys/THOR/usr/ports/graphics/drm-612-kmod/work/drm-kmod-drm_v6.12.85_2/drivers/gpu/drm/drm_client.c:6:
In file included from /usr/src/sys/compat/linuxkpi/common/include/linux/iosys-map.h:6: In file
included from /usr/src/sys/compat/linuxkpi/common/include/linux/io.h:35: ./machine/vm.h:64:11:
error: use of undeclared identifier 'NULL' 64 |                 return (NULL);

-- 

A FreeBSD user