Re: [Qemu-devel] [PATCH v2] map 64-bit PCI BARs at location provided by emulator

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Oct 13, 2013 at 02:13:44PM +0200, Igor Mammedov wrote:
> Currently 64-bit PCI BARs are unconditionally mapped by BIOS right
> over 4G + RamSizeOver4G location, which doesn't allow to reserve
> extra space before 64-bit PCI window. For memory hotplug an extra
> RAM space might be reserved after present 64-bit RAM end and BIOS
> should map 64-bit PCI BARs after it.
> 
> Introduce "etc/pcimem64-start" romfile to provide BIOS a hint
> where it should start mapping of 64-bit PCI BARs. If romfile is
> missing, BIOS reverts to legacy behavior and starts mapping right
> after high memory.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> v2:
>   * place 64-bit window behind high RAM end if "etc/pcimem64-start"
>     points below it.

Hmm I had an alternative suggestion of passing smbios
tables in from QEMU (seabios already has a mechanism for this).
We could then simply increase the existing RamSize variable.

What do you think about this idea?


> ---
>  src/fw/pciinit.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> index b29db99..798309b 100644
> --- a/src/fw/pciinit.c
> +++ b/src/fw/pciinit.c
> @@ -18,6 +18,8 @@
>  #include "paravirt.h" // RamSize
>  #include "string.h" // memset
>  #include "util.h" // pci_setup
> +#include "byteorder.h" // le64_to_cpu
> +#include "romfile.h" // romfile_loadint
>  
>  #define PCI_DEVICE_MEM_MIN     0x1000
>  #define PCI_BRIDGE_IO_MIN      0x1000
> @@ -764,6 +766,15 @@ static void pci_bios_map_devices(struct pci_bus *busses)
>  {
>      if (pci_bios_init_root_regions(busses)) {
>          struct pci_region r64_mem, r64_pref;
> +        u64 ram64_end = 0x100000000ULL + RamSizeOver4G;
> +        u64 base64 = le64_to_cpu(romfile_loadint("etc/pcimem64-start",
> +                                 ram64_end));
> +        if (base64 < ram64_end) {
> +            dprintf(1, "ignorig etc/pcimem64-start [0x%llx] below present RAM, "
> +                       "placing 64-bit PCI window behind RAM end: %llx",
> +                        base64, ram64_end);
> +            base64 = ram64_end;
> +        }
>          r64_mem.list.first = NULL;
>          r64_pref.list.first = NULL;
>          pci_region_migrate_64bit_entries(&busses[0].r[PCI_REGION_TYPE_MEM],
> @@ -779,7 +790,7 @@ static void pci_bios_map_devices(struct pci_bus *busses)
>          u64 align_mem = pci_region_align(&r64_mem);
>          u64 align_pref = pci_region_align(&r64_pref);
>  
> -        r64_mem.base = ALIGN(0x100000000LL + RamSizeOver4G, align_mem);
> +        r64_mem.base = ALIGN(base64, align_mem);
>          r64_pref.base = ALIGN(r64_mem.base + sum_mem, align_pref);
>          pcimem64_start = r64_mem.base;
>          pcimem64_end = r64_pref.base + sum_pref;
> -- 
> 1.8.3.1