From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38876) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ce7CF-000102-G6 for qemu-devel@nongnu.org; Wed, 15 Feb 2017 16:33:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ce7CC-00004v-Cn for qemu-devel@nongnu.org; Wed, 15 Feb 2017 16:33:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54536) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ce7CC-0008WS-70 for qemu-devel@nongnu.org; Wed, 15 Feb 2017 16:33:04 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 23E588553C for ; Wed, 15 Feb 2017 21:33:04 +0000 (UTC) Date: Wed, 15 Feb 2017 14:33:01 -0700 From: Alex Williamson Message-ID: <20170215143301.363029a2@t450s.home> In-Reply-To: <1487191768-8489-1-git-send-email-mst@redhat.com> References: <1487191768-8489-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] pci/pcie: don't assume cap id 0 is reserved List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org, Peter Xu , Marcel Apfelbaum On Wed, 15 Feb 2017 22:49:47 +0200 "Michael S. Tsirkin" wrote: > VFIO actually wants to create a capability with ID == 0. > This is done to make guest drivers skip the given capability. > pcie_add_capability then trips up on this capability > when looking for end of capability list. > > To support this use-case, it's easy enough to switch to > e.g. 0xffffffff for these comparisons - we can be sure > it will never match a 16-bit capability ID. > > Signed-off-by: Michael S. Tsirkin > --- Reviewed-by: Alex Williamson > hw/pci/pcie.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c > index cbd4bb4..f4dd177 100644 > --- a/hw/pci/pcie.c > +++ b/hw/pci/pcie.c > @@ -610,7 +610,8 @@ bool pcie_cap_is_arifwd_enabled(const PCIDevice *dev) > * uint16_t ext_cap_size > */ > > -static uint16_t pcie_find_capability_list(PCIDevice *dev, uint16_t cap_id, > +/* Passing a cap_id value > 0xffff will return 0 and put end of list in prev */ > +static uint16_t pcie_find_capability_list(PCIDevice *dev, uint32_t cap_id, > uint16_t *prev_p) > { > uint16_t prev = 0; > @@ -679,9 +680,11 @@ void pcie_add_capability(PCIDevice *dev, > } else { > uint16_t prev; > > - /* 0 is reserved cap id. use internally to find the last capability > - in the linked list */ > - next = pcie_find_capability_list(dev, 0, &prev); > + /* > + * 0xffffffff is not a valid cap id (it's a 16 bit field). use > + * internally to find the last capability in the linked list. > + */ > + next = pcie_find_capability_list(dev, 0xffffffff, &prev); > > assert(prev >= PCI_CONFIG_SPACE_SIZE); > assert(next == 0);