From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pentafluge.infradead.org (pentafluge.infradead.org [213.146.154.40]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 7821D67B9C for ; Tue, 5 Sep 2006 15:07:59 +1000 (EST) Subject: Re: [POWERPC] merge iSeries i/o operations with the rest From: David Woodhouse To: Stephen Rothwell In-Reply-To: <20060905120817.e52857ee.sfr@canb.auug.org.au> References: <20060905120817.e52857ee.sfr@canb.auug.org.au> Content-Type: text/plain Date: Mon, 04 Sep 2006 22:07:50 -0700 Message-Id: <1157432871.2413.9.camel@shinybook.infradead.org> Mime-Version: 1.0 Cc: ppc-dev , paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2006-09-05 at 12:08 +1000, Stephen Rothwell wrote: > The low level i/o operations are now handled in iSeires by taking a > trap when we access the (inaccessible) io memory region and calling > the Hypervisor from the trap code. There was some discussion of the possibility of using the 'alternatives' mechanism to patch the I/O instructions at run-time when we find we've booted on iSeries -- just turning each one into a jump to a trampoline which does the appropriate hypervisor calls, thus avoiding the overhead of the trap each time. Was that approach not viable, or not noticeably less of a performance hit on iSeries? -- dwmw2