Date: Sun, 20 Apr 2003 22:53:32 -0700 From: Marcel Moolenaar <marcel@xcllnt.net> To: freebsd-hackers@FreeBSD.org Subject: Is pmap_kextract() allowed to fault? Message-ID: <20030421055332.GA4680@dhcp01.pn.xcllnt.net>
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Gang, On ia64 pmap_kextract() uses the tpa instruction which given a virtual address returns the physical address based on the translation registers and cache (ie TLB). This can fault when there's currently no mapping for the virtual address. Since all other architectures have a non-faulting implementation (AFAICT), I'm a bit worried that we might get into trouble on ia64. I couldn't find anything about pmap_kextract(), so maybe anybody can enlighten me: 1. Is pmap_kextract() allowed to fault? 2. Is pmap_kextract() used often enough that using the cpu's TLB is a possible performance speedup even if there are costly faults that can sometimes happen? Note: an implementation not based on the tpa instruction would look pretty much the same as the current sparc64 implementation. Just so you know... Thanks, -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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