Re: [Qemu-devel] [PATCH] q35: fix mmconfig and PCI0._CRS

[Igor Mammedov]

On Tue, 28 May 2019 22:43:31 +0200
Gerd Hoffmann <address@hidden> wrote:

> This patch changes the handling of the mmconfig area.  Thanks to the
> pci(e) expander devices we already have the logic to exclude address
> ranges from PCI0._CRS.  We can simply add the mmconfig address range
> to the list get it excluded as well.
> 
> With that in place we can go with a fixed pci hole which covers the
> whole area from the end of (low) ram to the ioapic.
> 
> This will make the whole logic alot less fragile.  No matter where the
> firmware places the mmconfig xbar, things should work correctly.  The
> guest also gets a bit more PCI address space (seabios boot):
> 
>     # cat /proc/iomem
>     [ ... ]
>     7ffdd000-7fffffff : reserved
>     80000000-afffffff : PCI Bus 0000:00            <<-- this is new
>     b0000000-bfffffff : PCI MMCONFIG 0000 [bus 00-ff]
>       b0000000-bfffffff : reserved
>     c0000000-febfffff : PCI Bus 0000:00
>       f8000000-fbffffff : 0000:00:01.0
>     [ ... ]
> 
> So this is a guest visible change.

My impression was that QEMU would/should add into CRS whatever bars
firmware programmed (and it looks like QEMU doesn't do it right).
So I'm not really fond of adding bigger hole just to paper over
existing bug (still might be the way to go). Let me ponder a bit
on it and look into what's isn't working on QEMU side properly.

> 
> Cc: László Érsek <address@hidden>
> Cc: Igor Mammedov <address@hidden>
> Signed-off-by: Gerd Hoffmann <address@hidden>
> ---
>  hw/i386/acpi-build.c | 14 ++++++++++++++
>  hw/pci-host/q35.c    | 31 ++++++++-----------------------
>  2 files changed, 22 insertions(+), 23 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 0d78d738948c..abb0e0ce9f27 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -122,6 +122,8 @@ typedef struct FwCfgTPMConfig {
>      uint8_t tpmppi_version;
>  } QEMU_PACKED FwCfgTPMConfig;
>  
> +static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg);
> +
>  static void init_common_fadt_data(Object *o, AcpiFadtData *data)
>  {
>      uint32_t io = object_property_get_uint(o, ACPI_PM_PROP_PM_IO_BASE, NULL);
> @@ -1807,6 +1809,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>      CrsRangeSet crs_range_set;
>      PCMachineState *pcms = PC_MACHINE(machine);
>      PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
> +    AcpiMcfgInfo mcfg;
>      uint32_t nr_mem = machine->ram_slots;
>      int root_bus_limit = 0xFF;
>      PCIBus *bus = NULL;
> @@ -1921,6 +1924,17 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>          }
>      }
>  
> +    /*
> +     * At this point crs_range_set has all the ranges used by pci
> +     * busses *other* than PCI0.  These ranges will be excluded from
> +     * the PCI0._CRS.  Add mmconfig to the set so it will be excluded
> +     * too.
> +     */
> +    if (acpi_get_mcfg(&mcfg)) {
> +        crs_range_insert(crs_range_set.mem_ranges,
> +                         mcfg.base, mcfg.base + mcfg.size - 1);
> +    }
> +
>      scope = aml_scope("\\_SB.PCI0");
>      /* build PCI0._CRS */
>      crs = aml_resource_template();
> diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
> index 960939f5ed3e..72093320befe 100644
> --- a/hw/pci-host/q35.c
> +++ b/hw/pci-host/q35.c
> @@ -258,15 +258,6 @@ static void q35_host_initfn(Object *obj)
>      object_property_add_link(obj, MCH_HOST_PROP_IO_MEM, TYPE_MEMORY_REGION,
>                               (Object **) &s->mch.address_space_io,
>                               qdev_prop_allow_set_link_before_realize, 0, 
> NULL);
> -
> -    /* Leave enough space for the biggest MCFG BAR */
> -    /* TODO: this matches current bios behaviour, but
> -     * it's not a power of two, which means an MTRR
> -     * can't cover it exactly.
> -     */
> -    range_set_bounds(&s->mch.pci_hole,
> -            MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT + MCH_HOST_BRIDGE_PCIEXBAR_MAX,
> -            IO_APIC_DEFAULT_ADDRESS - 1);
>  }
>  
>  static const TypeInfo q35_host_info = {
> @@ -338,20 +329,6 @@ static void mch_update_pciexbar(MCHPCIState *mch)
>      }
>      addr = pciexbar & addr_mask;
>      pcie_host_mmcfg_update(pehb, enable, addr, length);
> -    /* Leave enough space for the MCFG BAR */
> -    /*
> -     * TODO: this matches current bios behaviour, but it's not a power of 
> two,
> -     * which means an MTRR can't cover it exactly.
> -     */
> -    if (enable) {
> -        range_set_bounds(&mch->pci_hole,
> -                         addr + length,
> -                         IO_APIC_DEFAULT_ADDRESS - 1);
> -    } else {
> -        range_set_bounds(&mch->pci_hole,
> -                         MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT,
> -                         IO_APIC_DEFAULT_ADDRESS - 1);
> -    }
>  }
>  
>  /* PAM */
> @@ -484,6 +461,14 @@ static void mch_update(MCHPCIState *mch)
>      mch_update_pam(mch);
>      mch_update_smram(mch);
>      mch_update_ext_tseg_mbytes(mch);
> +
> +    /*
> +     * pci hole goes from end-of-low-ram to io-apic.
> +     * mmconfig will be excluded by the dsdt builder.
> +     */
> +    range_set_bounds(&mch->pci_hole,
> +                     mch->below_4g_mem_size,
> +                     IO_APIC_DEFAULT_ADDRESS - 1);
>  }
>  
>  static int mch_post_load(void *opaque, int version_id)