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pcie: enable Extended tag field support

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>From what I read PCI has 32 transactions, PCI Express devices can handle
256 with Extended tag enabled (spec mentions also larger values but I
lack PCIe knowledge).

QEMU leaves 'Extended tag field' with 0 as value:

Capabilities: [e0] Express (v1) Root Complex Integrated Endpoint, IntMsgNum 0
        DevCap: MaxPayload 128 bytes, PhantFunc 0
                ExtTag- RBE+ FLReset- TEE-IO-

SBSA ACS has test 824 which checks for PCIe device capabilities. BSA
specification [1] (SBSA is on top of BSA) in section F.3.2 lists
expected values for Device Capabilities Register:

Device Capabilities Register     Requirement
Role based error reporting       RCEC and RCiEP: Hardwired to 1
Endpoint L0s acceptable latency  RCEC and RCiEP: Hardwired to 0
L1 acceptable latency            RCEC and RCiEP: Hardwired to 0
Captured slot power limit scale  RCEC and RCiEP: Hardwired to 0
Captured slot power limit value  RCEC and RCiEP: Hardwired to 0
Max payload size                 value must be compliant with PCIe spec
Phantom functions                RCEC and RCiEP: Recommendation is to
                                 hardwire this bit to 0.
Extended tag field               Hardwired to 1

1. https://developer.arm.com/documentation/den0094/c/

This change enables Extended tag field. All versioned platforms should
have it disabled for older versions (tested with Arm/virt).

Signed-off-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Message-Id: <20241023113820.486017-1-marcin.juszkiewicz@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Marcin Juszkiewicz 2024-10-23 13:38:20 +02:00 • committed by Michael S. Tsirkin
parent 6ce12bd297
commit 449dca6ac9
4 changed files with 14 additions and 2 deletions
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2
hw/pci/pci.c
View file

@ -100,6 +100,8 @@ static Property pci_props[] = {
QEMU_PCIE_ARI_NEXTFN_1_BITNR, false),
DEFINE_PROP_SIZE32("x-max-bounce-buffer-size", PCIDevice,
max_bounce_buffer_size, DEFAULT_MAX_BOUNCE_BUFFER_SIZE),
DEFINE_PROP_BIT("x-pcie-ext-tag", PCIDevice, cap_present,
QEMU_PCIE_EXT_TAG_BITNR, true),
{ .name = "busnr", .info = &prop_pci_busnr },
DEFINE_PROP_END_OF_LIST()
};