Re: [PATCH v2 0/4] Add extra pci roots support for Arm

Laszlo Ersek

+Alex, +Ray

comment below

On 12/04/20 07:48, Jiahui Cen wrote:
Hi Laszlo,

During the modification of this patch series, I got a confusing problem
that the EDK2's Alignment seems not fit with Linux on ARM.

EDK2, in CalculateResourceAperture, aligns the offset of child nodes
in descending order and uses the *Bridge's alignment* to align the
total length of Bridge.

However, Linux, in pbus_size_mem, would align the size of child nodes
and use *the half of max alignment of child nodes* to align the total
length of Bridge.

eg. A Root Bridge with Bus [d2]
where [d2:01.00] is a pcie-pci-bridge with BAR0 (mem, 64-bit, non-pref) [size=256]
[d3:01.00] is a PCI Device with BAR0 (mem, 64-bit, pref) [size=128K]
BAR4 (mem, 64-bit, pref) [size=64M]

In EDK2, the Resource Map would be:
PciBus: Resource Map for Root Bridge PciRoot(0xD2)
Type = Mem64; Base = 0x8004000000; Length = 0x4200000; Alignment = 0x3FFFFFF
Base = 0x8004000000; Length = 0x4100000; Alignment = 0x3FFFFFF; Owner = PPB [D2|01|00:**]; Type = PMem64
Base = 0x8008100000; Length = 0x100; Alignment = 0xFFF; Owner = PPB [D2|01|00:10]

PciBus: Resource Map for Bridge [D2|01|00]
Type = PMem64; Base = 0x8004000000; Length = 0x4100000; Alignment = 0x3FFFFFF
Base = 0x8004000000; Length = 0x4000000; Alignment = 0x3FFFFFF; Owner = PCI [D3|01|00:20]
Base = 0x8008000000; Length = 0x20000; Alignment = 0x1FFFF; Owner = PCI [D3|01|00:10]
Type = Mem64; Base = 0x8008100000; Length = 0x100; Alignment = 0xFFF

It shows that with EDK2's alignment [d2:01.00] only requires
a PMem64 resource range of 0x4100000.

However in Linux, [d2:01.00]'s BAR14 (Prefetchable Memory
Resource behind the Bridge) requires a PMem64 resource range
of 0x06000000, which comes from (0x4000000 + 0x20000) with
alignment=0x1FFFFFF the half of the max alignment 0x3FFFFFF.

Therefore, the assignment for [d2:01.00]'s BAR14 will fail.

The difference could make the resource range allocated in EDK2 smaller
than the resource range needed in Linux, which causes the assignment
failure in Linux.

The same difference also occurs when io resource allocation.

To handle this senario, is it necessary to calculate the resource map
in Linux way?
I don't know why this difference in BAR placement exists between edk2
and Linux, and/or perhaps even between x86_64 Linux and aarch64 Linux. I
don't really remember seeing this issue with OVMF.

It could have something to do with differences in ACPI table composition
as well.

I don't know if we've ever tested hotplug behind pxb.

Furthermore, Linux Kernel will treat pcie-root-port as a hotplugable
bridge and try to require more resource. But EDK2 seems not support
hotplug padding for ARM?
Try including "OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.inf" in
ArmVirtQemu. See commit fe4049471bdf for documentation.

QEMU's pcie-root-port device should expose the same reservation/padding
properties to the user when using the "virt" machine of
qemu-system-aarch64, I think.



On 2020/11/11 22:33, Laszlo Ersek wrote:
On 11/09/20 14:05, Jiahui Cen wrote:
Changes with v1
Separated into four patches.
Factor the same logic parts into a new library.

(1) Each commit message in the series should reference this bugzilla.

But, in itself, that's no reason for a repost; such an update can be
made by maintainers when they merge the series.

(2) This is a feature addition, so it's merge material for the next
development cycle
(Also it depends on the QEMU work being merged first.) I'm going to
proceed with the review now.



This patch series adds support for extra pci roots for ARM.

In order to avoid duplicated codes, we introduce a new library
PciHostBridgeUtilityLib which extracts common interfaces from
OvmfPkg/PciHostBridgeLib. It provides conflicts informing and extra pci
roots scanning. Using the utility lib, the uefi could scan for extra
root buses and recognize multiple roots for ARM.

Cc: Jordan Justen <jordan.l.justen@...>
Cc: Laszlo Ersek <lersek@...>
Cc: Ard Biesheuvel <ard.biesheuvel@...>
Cc: Leif Lindholm <leif@...>
Signed-off-by: Yubo Miao <miaoyubo@...>
Signed-off-by: Jiahui Cen <cenjiahui@...>

Yubo Miao (4):
OvmfPkg: Extract functions form PciHostBridgeLib
ArmVirtPkg: Use extracted PciHostBridgeUtilityLib
OvmfPkg: Extract functions of extra pci roots
ArmVirtPkg: Support extra pci roots

ArmVirtPkg/ | 1 +
OvmfPkg/OvmfPkgIa32.dsc | 1 +
OvmfPkg/OvmfPkgIa32X64.dsc | 1 +
OvmfPkg/OvmfPkgX64.dsc | 1 +
OvmfPkg/OvmfXen.dsc | 1 +
ArmVirtPkg/Library/FdtPciHostBridgeLib/FdtPciHostBridgeLib.inf | 5 +
OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf | 1 +
OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.inf | 51 ++++
OvmfPkg/Include/Library/PciHostBridgeUtilityLib.h | 98 +++++++
ArmVirtPkg/Library/FdtPciHostBridgeLib/FdtPciHostBridgeLib.c | 221 ++++++++-------
OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c | 234 +---------------
OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.c | 283 ++++++++++++++++++++
12 files changed, 563 insertions(+), 335 deletions(-)
create mode 100644 OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.inf
create mode 100644 OvmfPkg/Include/Library/PciHostBridgeUtilityLib.h
create mode 100644 OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.c


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