amd64/178357: [patch] export CPU physical and virtual address sizes in sysctl oids using do_cpuid

[John Baldwin]

On Sunday, May 05, 2013 6:43:54 pm Sofian Brabez wrote:
> 
> >Number:         178357
> >Category:       amd64
> >Synopsis:       [patch] export CPU physical and virtual address sizes in 
sysctl oids using do_cpuid
> >Confidential:   no
> >Severity:       non-critical
> >Priority:       low
> >Responsible:    freebsd-amd64
> >State:          open
> >Quarter:        
> >Keywords:       
> >Date-Required:
> >Class:          change-request
> >Submitter-Id:   current-users
> >Arrival-Date:   Sun May 05 22:50:00 UTC 2013
> >Closed-Date:
> >Last-Modified:
> >Originator:     Sofian Brabez
> >Release:        FreeBSD 10.0-CURRENT amd64
> >Organization:
> >Environment:
> System: FreeBSD ogoshi.lan 10.0-CURRENT FreeBSD 10.0-CURRENT #3 r250287M: 
Sun May 5 21:59:15 CEST 2013 
root at ogoshi.lan:/usr/obj/usr/home/sbz/freebsd/svn/src/sys/GENERIC amd64
> 
> >Description:
> This patch export CPU Physical and Virtual address sizes through the sysctl 
interface
> using do_cpuid function.
> 
> It also patch the sys/modules/linprocfs module add this information in the
> /usr/compat/linux/proc/cpuinfo output like it's done in Linux /proc/cpuinfo.
> 
> More details can be found here: http://people.freebsd.org/~sbz/cpu/
> >How-To-Repeat:
> >Fix:
> 
> Apply the given patch.
> 
> --- address_sizes.diff begins here ---
> Index: amd64/amd64/identcpu.c
> ===================================================================
> --- amd64/amd64/identcpu.c	(revision 250287)
> +++ amd64/amd64/identcpu.c	(working copy)
> @@ -109,6 +109,12 @@
>  SYSCTL_INT(_hw, OID_AUTO, clockrate, CTLFLAG_RD, 
>      &hw_clockrate, 0, "CPU instruction clock rate");
>  
> +SYSCTL_UINT(_machdep, OID_AUTO, cpu_physical_address_bits, CTLFLAG_RD,
> +    &cpu_pma_bits, 0, "CPU physical address bits");
> +
> +SYSCTL_UINT(_machdep, OID_AUTO, cpu_virtual_address_bits, CTLFLAG_RD,
> +    &cpu_vma_bits, 0, "CPU virtual address bits");
> +
>  static eventhandler_tag tsc_post_tag;
>  
>  static char cpu_brand[48];
> @@ -516,6 +522,16 @@
>  	cpu_feature = regs[3];
>  	cpu_feature2 = regs[2];
>  
> +	/* Intel CPUID Specification chapter 5.2.7 
> +	 * eax=0x80000008
> +	 * */
> +	do_cpuid(0x80000008, regs);
> +
> +	/* upper bits are virtual size */
> +	cpu_vma_bits = ((regs[0] >> 8) & 0xFF);
> +	/* lower bits are physical size */
> +	cpu_pma_bits = (regs[0] & 0xFF);
> +
>  	/*
>  	 * Clear "Limit CPUID Maxval" bit and get the largest standard CPUID
>  	 * function number again if it is set from BIOS.  It is necessary
> Index: amd64/amd64/initcpu.c
> ===================================================================
> --- amd64/amd64/initcpu.c	(revision 250287)
> +++ amd64/amd64/initcpu.c	(working copy)
> @@ -66,10 +66,12 @@
>  u_int	cpu_high;		/* Highest arg to CPUID */
>  u_int	cpu_exthigh;		/* Highest arg to extended CPUID */
>  u_int	cpu_id;			/* Stepping ID */
> +u_int	cpu_pma_bits;		/* CPU physical address bits */
>  u_int	cpu_procinfo;		/* HyperThreading Info / Brand Index / CLFUSH 
*/
>  u_int	cpu_procinfo2;		/* Multicore info */
>  char	cpu_vendor[20];		/* CPU Origin code */
>  u_int	cpu_vendor_id;		/* CPU vendor ID */
> +u_int	cpu_vma_bits;		/* CPU virtual address bits */
>  u_int	cpu_fxsr;		/* SSE enabled */
>  u_int	cpu_mxcsr_mask;		/* Valid bits in mxcsr */
>  u_int	cpu_clflush_line_size = 32;
> Index: amd64/include/md_var.h
> ===================================================================
> --- amd64/include/md_var.h	(revision 250287)
> +++ amd64/include/md_var.h	(working copy)
> @@ -54,10 +54,12 @@
>  extern	u_int	cpu_id;
>  extern	u_int	cpu_max_ext_state_size;
>  extern	u_int	cpu_mxcsr_mask;
> +extern u_int	cpu_pma_bits;
>  extern	u_int	cpu_procinfo;
>  extern	u_int	cpu_procinfo2;
>  extern	char	cpu_vendor[];
>  extern	u_int	cpu_vendor_id;
> +extern u_int	cpu_vma_bits;
>  extern	char	ctx_switch_xsave[];
>  extern	char	kstack[];
>  extern	char	sigcode[];
> Index: compat/linprocfs/linprocfs.c
> ===================================================================
> --- compat/linprocfs/linprocfs.c	(revision 250287)
> +++ compat/linprocfs/linprocfs.c	(working copy)
> @@ -310,6 +310,12 @@
>  		    fqmhz, fqkhz, fqmhz, fqkhz);
>  	}
>  
> +	if (cpu_vma_bits != 0 && cpu_vma_bits != 0) {

I think you want s/vma/pma/ here for the first check.

> +		sbuf_printf(sb,
> +		    "address sizes\t: %u bits physical, %u bits virtual\n",
> +		    cpu_pma_bits, cpu_vma_bits);
> +	}
> +
>  	return (0);
>  }
>  #endif /* __i386__ || __amd64__ */

I don't know that we need to create new sysctls for this since userland 
processes can just run cpuid directly.  I would be fine adding this to 
linprocfs however.

I think if we want to start exporting cpuid info via sysctl we should think 
about designing a consistent interface for doing so rather than adding ad-hoc 
sysctls for certain fields.

-- 
John Baldwin