Am 14.12.2012 13:13, schrieb Alexander Graf: > From: Bharat Bhushan <r65...@freescale.com> > > PCI Root complex have TYPE-1 configuration header while PCI endpoint > have type-0 configuration header. The type-1 configuration header have > a BAR (BAR0). In Freescale PCI controller BAR0 is used for mapping pci > address space to CCSR address space. This can used for 2 purposes: 1) > for MSI interrupt generation 2) Allow CCSR registers access when configured > as PCI endpoint, which I am not sure is a use case with QEMU-KVM guest. > > What I observed is that when guest read the size of BAR0 of host controller > configuration header (TYPE1 header) then it always reads it as 0. When > looking into the QEMU hw/ppce500_pci.c, I do not find the PCI controller > device registering BAR0. I do not find any other controller also doing so > may they do not use BAR0. > > There are two issues when BAR0 is not there (which I can think of): > 1) There should be BAR0 emulated for PCI Root complex (TYPE1 header) and > when reading the size of BAR0, it should give size as per real h/w. > > 2) Do we need this BAR0 inbound address translation? > When BAR0 is of non-zero size then it will be configured for PCI > address space to local address(CCSR) space translation on inbound access. > The primary use case is for MSI interrupt generation. The device is > configured with an address offsets in PCI address space, which will be > translated to MSI interrupt generation MPIC registers. Currently I do > not understand the MSI interrupt generation mechanism in QEMU and also > IIRC we do not use QEMU MSI interrupt mechanism on e500 guest machines. > But this BAR0 will be used when using MSI on e500. > > I can see one more issue, There are ATMUs emulated in hw/ppce500_pci.c, > but i do not see these being used for address translation. > So far that works because pci address space and local address space are 1:1 > mapped. BAR0 inbound translation + ATMU translation will complete the address > translation of inbound traffic. > > Signed-off-by: Bharat Bhushan <bharat.bhus...@freescale.com> > [agraf: fix double variable assignment w/o read] > Signed-off-by: Alexander Graf <ag...@suse.de>
Reviewed-by: Andreas Färber <afaer...@suse.de> Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
