Date: Sat, 30 Sep 1995 22:50:18 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, davidg@Root.COM Cc: hackers@freebsd.org, julian@ref.tfs.com Subject: Re: correctness of isa.c Message-ID: <199509301250.WAA02664@godzilla.zeta.org.au>
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> It has no i386 dependencies as far as the interface of the function, but the >function itself has almost no independencies. :-) This makes it (pmap_mapdev()) like cpu_switch() - machine-dependent internally but worth having for all arch's. >> Why doesn't VM distinguish between the types of physical and virtual >>addresses? > I don't understand this question. Different types? Do you mean kernel/user >or managed/unmanaged, or what? The same C type, vm_offset_t, is used for both physical and virtual addresses. This is bad if physical addresses have a different number of bits than virtual addresses and the type big enough for both is too inefficient or isn't a scalar type. E.g., i386 virtual addresses really have 16 bits of segment info and 32 bits of offset. We can get away with not supporting them generally only because there is no way the general case can be efficient so no one wants it. Bruce
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