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Re: [PATCH 1/3] ppc/pnv: Tune the POWER9 PCIe Host bridge model

From: Frederic Barrat
Subject: Re: [PATCH 1/3] ppc/pnv: Tune the POWER9 PCIe Host bridge model
Date: Mon, 29 Nov 2021 15:40:38 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0

On 26/11/2021 10:09, Cédric Le Goater wrote:
On 11/16/21 18:01, Frederic Barrat wrote:
The PHB v4 found on POWER9 doesn't request any LSI, so let's clear the
Interrupt Pin register in the config space so that the model matches
the hardware.

If we don't, then we inherit from the default pcie root bridge, which
requests a LSI. And because we don't map it correctly in the device
tree, all PHBs allocate the same bogus hw interrupt. We end up with
inconsistent interrupt controller (xive) data. The problem goes away
if we don't allocate the LSI in the first place.

Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
  hw/pci-host/pnv_phb4.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
index 5c375a9f28..1659d55b4f 100644
--- a/hw/pci-host/pnv_phb4.c
+++ b/hw/pci-host/pnv_phb4.c
@@ -1234,10 +1234,13 @@ static void pnv_phb4_reset(DeviceState *dev)
      PCIDevice *root_dev = PCI_DEVICE(&phb->root);
-     * Configure PCI device id at reset using a property.
+     * Configure the PCI device at reset:
+     *   - set the Vendor and Device ID to for the root bridge
+     *   - no LSI
      pci_config_set_vendor_id(root_dev->config, PCI_VENDOR_ID_IBM);
      pci_config_set_device_id(root_dev->config, phb->device_id);
+    pci_config_set_interrupt_pin(root_dev->config, 0);
  static const char *pnv_phb4_root_bus_path(PCIHostState *host_bridge,

FYI, I am seeing an issue with FreeBSD when booting from iso :


I see what's going on... Since the phb4 model borrows most of its code from the pcie_root bridge, there are several instances of code such as:

    if (msix_enabled(dev)) {
        do something;
    } else if (msi_enabled(dev)) {
        do something else;
    } else {
        yet something else which assumes a LSI;

With this series, I removed the LSI from the phb4 root port to match the hardware and fixed one such code pattern in patch 3. But there are others, and we hit one of those when installing from the free bsd iso.

So this is going to need more work.




SIGTERM received, booting...
KDB: debugger backends: ddb
KDB: current backend: ddb
Copyright (c) 1992-2021 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
     The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 14.0-CURRENT #0 main-n250301-4827bf76bce: Thu Oct 28 06:53:58 UTC 2021 root@releng1.nyi.freebsd.org:/usr/obj/usr/src/powerpc.powerpc64/sys/GENERIC64 powerpc FreeBSD clang version 12.0.1 (git@github.com:llvm/llvm-project.git llvmorg-12.0.1-0-gfed41342a82f)
WARNING: WITNESS option enabled, expect reduced performance.
VT: init without driver.
ofw_initrd: initrd loaded at 0x28000000-0x28c7928c
cpu0: IBM POWER9 revision 2.0, 1000.00 MHz
cpu0: Features dc007182<PPC32,PPC64,ALTIVEC,FPU,MMU,SMT,ISNOOP,ARCH205,ARCH206,VSX,TRUELE> cpu0: Features2 bee00000<ARCH207,DSCR,ISEL,TAR,VCRYPTO,ARCH300,IEEE128,DARN>
real memory  = 1014484992 (967 MB)
avail memory = 117903360 (112 MB)
random: registering fast source PowerISA DARN random number generator
random: fast provider: "PowerISA DARN random number generator"
arc4random: WARNING: initial seeding bypassed the cryptographic random device because it was not yet seeded and the knob 'bypass_before_seeding' was enabled.
random: entropy device external interface
kbd0 at kbdmux0
ofwbus0: <Open Firmware Device Tree> on nexus0
opal0: <OPAL Abstraction Firmware> irq 1048560,1048561,1048562,1048563,1048564,1048565,1048566,1048567,1048568,1048569,1048570,1048571,1048572,1048573 on ofwbus0
opal0: registered as a time-of-day clock, resolution 0.002000s
simplebus0: <Flattened device tree simple bus> mem 0x6030000000000-0x60300ffffffff on ofwbus0 pcib0: <OPAL Host-PCI bridge> mem 0x600c3c0000000-0x600c3c0000fff,0x600c300000000-0x600c30fffffff on ofwbus0
pci0: <OFW PCI bus> numa-domain 0 on pcib0
qemu-system-ppc64: ../hw/pci/pci.c:1487: pci_irq_handler: Assertion `0 <= irq_num && irq_num < PCI_NUM_PINS' failed.

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