[Qemu-devel] Re: [PATCH 3/5] Use the correct mask to size the PCI option ROM BAR.

[Gleb Natapov <gleb@redhat.com>]

On Mon, Oct 12, 2009 at 01:03:36PM +0200, Michael S. Tsirkin wrote:
> On Mon, Oct 12, 2009 at 12:08:21PM +0200, Gleb Natapov wrote:
> > On Mon, Oct 12, 2009 at 11:52:25AM +0200, Michael S. Tsirkin wrote:
> > > On Mon, Oct 12, 2009 at 08:50:24AM +0200, Gleb Natapov wrote:
> > > > Send patch with your favorite interpretation to qemu pcbios/seabios.
> > > > The regression concern from my previous mail applicable here as well.
> > > 
> > > Okay. Can you ack the following?
> > > 
> > I can if you'll add PCI spec reference for me to double check.
> 
> 
> > Also I prefer strict spec reading :)
> 
> OK, the issue is that reserved bits in BARs are not
> defined as read-only.  So here's a strict one:
> can you ack?
> 
> --->
> 
> seabios: fix ROM and I/O sizing
> 
> For ROM BARs, bit 0 is writeable (enable bit), which we not
> only don't want to set, but it will stick and make us think
> it's an I/O port resource.
> Further, PCI spec defines the following bits as reserved:
> - bit 1 in I/O BAR
> - bits 10:1 in ROM BAR
> and we should be careful and write 0 there.
> For memory, bits 0-3 are reserved, so it's safe to handle it
> in the same way as I/O.
> 
> See 6.2.5.1 for I/O and memory, and 6.2.5.2 for ROM;
> pages 225 and 228 in PCI spec revision 3.0.
> 
Section 6.2.5.1 says:
Software saves the original value of the Base Address register, writes
0 FFFF FFFFh to the register, then reads it back.

Section 6.2.5.2 says:
Device independent configuration software can determine how much address
space the device requires by writing a value of all 1's to the address
portion of the register and then reading the value back. (address
portion are bits 31-11).

So we should write PCI_ROM_ADDRESS_MASK in case of ROM and 0xffffffff
in case of regular BAR.

> See also Qemu pcbios commit 6ddb9f5c742b2b82b1755d7ec2a127f6e20e3806
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  src/pciinit.c |    8 +++++---
>  1 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/pciinit.c b/src/pciinit.c
> index 1d0f784..29b3901 100644
> --- a/src/pciinit.c
> +++ b/src/pciinit.c
> @@ -139,11 +139,13 @@ static void pci_bios_init_device(u16 bdf)
>              int ofs;
>              u32 val, size;
>  
> -            if (i == PCI_ROM_SLOT)
> +            if (i == PCI_ROM_SLOT) {
>                  ofs = PCI_ROM_ADDRESS;
> -            else
> +                pci_config_writel(bdf, ofs, PCI_ROM_ADDRESS_MASK);
> +            } else {
>                  ofs = PCI_BASE_ADDRESS_0 + i * 4;
> -            pci_config_writel(bdf, ofs, 0xffffffff);
> +                pci_config_writel(bdf, ofs, PCI_BASE_ADDRESS_IO_MASK);
> +            }
>              val = pci_config_readl(bdf, ofs);
>              if (val != 0) {
>                  size = (~(val & ~0xf)) + 1;
> -- 
> 1.6.3.3
> 
> 

--
			Gleb.