On 3/7/24 12:05, Manivannan Sadhasivam wrote:
Qcom SoCs making use of ARM SMMU require BDF to SID translation table in
the driver to properly map the SID for the PCIe devices based on their BDF
identifier. This is currently achieved with the help of
qcom_pcie_config_sid_1_9_0() function for SoCs supporting the 1_9_0 config.
But With newer Qcom SoCs starting from SM8450, BDF to SID translation is
set to bypass mode by default in hardware. Due to this, the translation
table that is set in the qcom_pcie_config_sid_1_9_0() is essentially
unused and the default SID is used for all endpoints in SoCs starting from
SM8450.
This is a security concern and also warrants swapping the DeviceID in DT
while using the GIC ITS to handle MSIs from endpoints. The swapping is
currently done like below in DT when using GIC ITS:
/*
* MSIs for BDF (1:0.0) only works with Device ID 0x5980.
* Hence, the IDs are swapped.
*/
msi-map = <0x0 &gic_its 0x5981 0x1>,
<0x100 &gic_its 0x5980 0x1>;
Here, swapping of the DeviceIDs ensure that the endpoint with BDF (1:0.0)
gets the DeviceID 0x5980 which is associated with the default SID as per
the iommu mapping in DT. So MSIs were delivered with IDs swapped so far.
But this also means the Root Port (0:0.0) won't receive any MSIs (for PME,
AER etc...)
So let's fix these issues by clearing the BDF to SID bypass mode for all
SoCs making use of the 1_9_0 config. This allows the PCIe devices to use
the correct SID, thus avoiding the DeviceID swapping hack in DT and also
achieving the isolation between devices.
Cc: <stable@xxxxxxxxxxxxxxx> # 5.11
Fixes: 4c9398822106 ("PCI: qcom: Add support for configuring BDF to SID mapping for SM8250")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
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Looks sensible..
Does switching away from bypass show any performance degradation?
Konrad
