From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=37211 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PDIB3-00070T-My for qemu-devel@nongnu.org; Tue, 02 Nov 2010 10:49:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PDHlZ-0004lI-Ej for qemu-devel@nongnu.org; Tue, 02 Nov 2010 10:23:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54731) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PDHlZ-0004l4-7v for qemu-devel@nongnu.org; Tue, 02 Nov 2010 10:23:13 -0400 From: Alex Williamson In-Reply-To: <20101102140736.GB29373@redhat.com> References: <20101102053544.10424.42769.stgit@s20.home> <20101102053751.10424.7525.stgit@s20.home> <20101102092508.GA3390@redhat.com> <1288706438.3045.7.camel@x201> <20101102140736.GB29373@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 02 Nov 2010 08:23:10 -0600 Message-ID: <1288707790.3045.18.camel@x201> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH 3/3] msi: Store the capability size in PCIDevice List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: yamahata@valinux.co.jp, qemu-devel@nongnu.org On Tue, 2010-11-02 at 16:07 +0200, Michael S. Tsirkin wrote: > On Tue, Nov 02, 2010 at 08:00:38AM -0600, Alex Williamson wrote: > > On Tue, 2010-11-02 at 11:25 +0200, Michael S. Tsirkin wrote: > > > On Mon, Nov 01, 2010 at 11:37:53PM -0600, Alex Williamson wrote: > > > > Avoid needing to get the MSI capability flags every time we need to > > > > check the capability length. This also makes it accessible outside > > > > of msi.c, making it easier for users to filter config space writes > > > > using msi_cap and msi_cap_size. > > > > > > I think for this last use-case, we are better off with returning a > > > boolean from msi_write_config which tells us whether the write is in > > > range. This has the advantage in that it will also work well for other > > > capabilities. Or second best, if that is insufficient for some reason, > > > export an msi_cap_size function. > > > > Returning whether the write was in range isn't enough. For device > > assignment, I need to know whether the capability was enabled or > > disabled. This currently means checking the enable state before and > > after calling msi_write_config and doing the appropriate backend setup. > > Sounds good. Why does this mean you need the capability size? > bool was_enabled = msi_enabled(dev); > msi_write_config(..) > if (was_enabled != msi_enabled(dev)) { > } Because this code makes me sad... bool msi_was_enabled, msix_was_enabled, msi_is_enabled, msix_is_enabled; msi_was_enabled = msi_enabled(dev); msix_was_enabled = msix_enabled(dev); pci_default_write_config(... msi_write_config(... msix_write_config(... msi_is_enabled = msi_enabled(dev); msix_is_enabled = msix_enabled(dev); if (msi_was_enabled && !msi_is_enabled) disable_msi(... if (!msi_was_enabled && msi_is_enabled) enable_msi(... if (msix_was_enabled && !msix_is_enabled) disable_msi(... if (!msix_was_enabled && msix_is_enabled) enable_msix(... Confining msi tests to an msi related write and msix tests to an msix related write makes me slightly happier. I really think we need callbacks though so common msi/msix code can figure out if we've made a transition. Alex > > I think the only way I could blindly call the msi/x write config > > routines is if we init the capability with enable/disable callbacks. > > I'd be ok with an msi_cap_size function if we don't want to go that far > > too. What do you prefer? Thanks,