Date: Thu, 2 Dec 2010 09:46:03 -0500 From: Andrew Duane <aduane@juniper.net> To: Warner Losh <imp@bsdimp.com>, "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org>, Alan Cox <alc@cs.rice.edu> Subject: RE: vm_page_startup() Message-ID: <AC6674AB7BC78549BB231821ABF7A9AE9079119F4B@EMBX01-WF.jnpr.net> In-Reply-To: <4CF71F79.3020500@bsdimp.com> References: <4CF5E518.20508@rice.edu>,<4CF71F79.3020500@bsdimp.com>
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I much prefer the latter suggestion: making the code #ifdef'd on a feature,=
and having each platform define (or not) the feature. I've seen what happe=
ns when code in this space grows too many architecture ifdef's.....
--
Andrew Duane Juniper Networks
978-589-0551 10 Technology Park Dr
aduane@juniper.net Westford, MA 01886-3418
________________________________________
From: owner-freebsd-mips@freebsd.org [owner-freebsd-mips@freebsd.org] On Be=
half Of Warner Losh [imp@bsdimp.com]
Sent: Wednesday, December 01, 2010 11:24 PM
To: freebsd-mips@freebsd.org; Alan Cox
Subject: Re: vm_page_startup()
On 11/30/2010 23:03, Alan Cox wrote:
> Given this bit of code in the MIPS pmap:
>
> vm_offset_t
> pmap_map(vm_offset_t *virt, vm_offset_t start, vm_offset_t end, int prot)
> {
> vm_offset_t va, sva;
>
> if (MIPS_DIRECT_MAPPABLE(end))
> return (MIPS_PHYS_TO_DIRECT(start));
All mips architectures have at least a small direct map...
> The following in vm_page_startup() can apply to MIPS (as well as amd64):
>
> #ifdef __amd64__
> /*
> * pmap_map on amd64 comes out of the direct-map, not kvm like i386,
> * so the pages must be tracked for a crashdump to include this data.
> * This includes the vm_page_array and the early UMA bootstrap pages.
> */
> for (pa =3D new_end; pa < phys_avail[biggestone + 1]; pa +=3D PAGE_SIZ=
E)
> dump_add_page(pa);
> #endif
>
> Even if a particular MIPS-based machine didn't wind up using the
> direct map for the pmap_map calls in vm_page_startup() there would be
> no harm in having called dump_add_page(). On the other hand, if you
> don't call dump_add_page() when the direct map is used, you're crash
> dump will be missing some kernel data structures.
So would you suggest having:
#if defined(__mips__) || defined(__amd64__)
or
#if __VM_HAS_DIRECT_MAP
and adding that define to pmap.h for mips and amd64? I'm leaning to the
latter, since I don't like #ifdef arch in vm/* code on general
principles, but you're the maintainer...
Warner
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