Re: [Xen-devel] [PATCH v2] piix: define a TOM register to report the base of PCI

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

On Mon, Feb 25, 2013 at 02:53:37PM +0800, Xudong Hao wrote:
> v2:
> * Use "piix: " in the subject rather than "qemu: "
> * Define TOM register as one byte
> * Define default TOM value instead of hardcode 0xe0000000 in more that one 
> place
> * Use API pci_set_byte for pci config access
> * Use dev->config instead of the indirect d->dev.config
> 
> Define a TOM(top of memory) register to report the base of PCI memory, update
> memory region dynamically. TOM register are defined to one byte in PCI 
> configure
> space, because that only upper 4 bit of PCI memory takes effect for Xen, so
> it requires bios set TOM with 16M-aligned.
> 
> Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
> Signed-off-by: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>

Could you supply some motivation for this patch?

> ---
>  hw/pc.h       |  7 +++---
>  hw/pc_piix.c  | 12 +++-------
>  hw/piix_pci.c | 73 
> +++++++++++++++++++++++++++++++++++++++++++----------------
>  3 files changed, 59 insertions(+), 33 deletions(-)
> 
> diff --git a/hw/pc.h b/hw/pc.h
> index fbcf43d..62adcc5 100644
> --- a/hw/pc.h
> +++ b/hw/pc.h
> @@ -129,15 +129,14 @@ extern int no_hpet;
>  struct PCII440FXState;
>  typedef struct PCII440FXState PCII440FXState;
>  
> +#define I440FX_TOM     0xe0000000
> +#define I440FX_XEN_TOM 0xf0000000
> +
>  PCIBus *i440fx_init(PCII440FXState **pi440fx_state, int *piix_devfn,
>                      ISABus **isa_bus, qemu_irq *pic,
>                      MemoryRegion *address_space_mem,
>                      MemoryRegion *address_space_io,
>                      ram_addr_t ram_size,
> -                    hwaddr pci_hole_start,
> -                    hwaddr pci_hole_size,
> -                    hwaddr pci_hole64_start,
> -                    hwaddr pci_hole64_size,
>                      MemoryRegion *pci_memory,
>                      MemoryRegion *ram_memory);
>  
> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 0a6923d..2eef510 100644
> --- a/hw/pc_piix.c
> +++ b/hw/pc_piix.c
> @@ -93,9 +93,9 @@ static void pc_init1(MemoryRegion *system_memory,
>          kvmclock_create();
>      }
>  
> -    if (ram_size >= 0xe0000000 ) {
> -        above_4g_mem_size = ram_size - 0xe0000000;
> -        below_4g_mem_size = 0xe0000000;
> +    if (ram_size >= I440FX_TOM) {
> +        above_4g_mem_size = ram_size - I440FX_TOM;
> +        below_4g_mem_size = I440FX_TOM;
>      } else {
>          above_4g_mem_size = 0;
>          below_4g_mem_size = ram_size;
> @@ -130,12 +130,6 @@ static void pc_init1(MemoryRegion *system_memory,
>      if (pci_enabled) {
>          pci_bus = i440fx_init(&i440fx_state, &piix3_devfn, &isa_bus, gsi,
>                                system_memory, system_io, ram_size,
> -                              below_4g_mem_size,
> -                              0x100000000ULL - below_4g_mem_size,
> -                              0x100000000ULL + above_4g_mem_size,
> -                              (sizeof(hwaddr) == 4
> -                               ? 0
> -                               : ((uint64_t)1 << 62)),
>                                pci_memory, ram_memory);
>      } else {
>          pci_bus = NULL;
> diff --git a/hw/piix_pci.c b/hw/piix_pci.c
> index 3d79c73..3e5a25c 100644
> --- a/hw/piix_pci.c
> +++ b/hw/piix_pci.c
> @@ -86,6 +86,14 @@ struct PCII440FXState {
>  #define I440FX_PAM_SIZE 7
>  #define I440FX_SMRAM    0x72
>  
> +/* The maximum vaule of TOM(top of memory) register in I440FX
> + * is 1G, so it doesn't meet any popular virutal machines, so
> + * define another register to report the base of PCI memory.
> + * Use one byte 0xb0 for the upper 8 bit, they are originally
> + * resevered for host bridge.
> + * */
> +#define I440FX_PCI_HOLE_BASE 0xb0

Do you have to use a fixed address? As others said, it's a hack.
How about adding a special device for this hackery?

> +
>  static void piix3_set_irq(void *opaque, int pirq, int level);
>  static PCIINTxRoute piix3_route_intx_pin_to_irq(void *opaque, int pci_intx);
>  static void piix3_write_config_xen(PCIDevice *dev,
> @@ -101,6 +109,43 @@ static int pci_slot_get_pirq(PCIDevice *pci_dev, int 
> pci_intx)
>      return (pci_intx + slot_addend) & 3;
>  }
>  
> +
> +static void i440fx_update_pci_mem_hole(PCII440FXState *f, bool del)
> +{
> +    ram_addr_t above_4g_mem_size;
> +    hwaddr pci_hole_start, pci_hole_size, pci_hole64_start, pci_hole64_size;
> +
> +    pci_hole_start = pci_default_read_config(&f->dev, I440FX_PCI_HOLE_BASE, 
> 1) << 24;
> +    pci_hole_size = 0x100000000ULL - pci_hole_start;
> +
> +    if (ram_size >= pci_hole_start) {
> +        above_4g_mem_size = ram_size - pci_hole_start;
> +    } else {
> +        above_4g_mem_size = 0;
> +    }
> +    pci_hole64_start = 0x100000000ULL + above_4g_mem_size;
> +    pci_hole64_size = sizeof(hwaddr) == 4 ? 0 : ((uint64_t)1 << 62);
> +
> +    if (del) {
> +        memory_region_del_subregion(f->system_memory, &f->pci_hole);
> +        if (pci_hole64_size) {
> +            memory_region_del_subregion(f->system_memory, 
> &f->pci_hole_64bit);
> +        }
> +    }
> +
> +    memory_region_init_alias(&f->pci_hole, "pci-hole", f->pci_address_space,
> +                             pci_hole_start, pci_hole_size);
> +    memory_region_add_subregion(f->system_memory, pci_hole_start, 
> &f->pci_hole);
> +    memory_region_init_alias(&f->pci_hole_64bit, "pci-hole64",
> +                             f->pci_address_space,
> +                             pci_hole64_start, pci_hole64_size);
> +    if (pci_hole64_size) {
> +        memory_region_add_subregion(f->system_memory, pci_hole64_start,
> +                                    &f->pci_hole_64bit);
> +    }
> +}
> +
> +

If you do things like this, won't ACPI tables become incorrect?

-- 
MST

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