From e90f6988d8dc9a910a849937a4c0c054b65d3903 Mon Sep 17 00:00:00 2001
From: Christian Helmuth <christian.helmuth@genode-labs.com>
Date: Thu, 23 May 2024 17:04:16 +0200
Subject: [PATCH] pci_decode: disable MSI/MSI-X capabilities

Default disabled initialization prevents follow-up errors if one
capability is already enabled on boot, but platform_drv decides to
enable the other one. The PCI spec explicitly states that "Behavior is
undefined if both MSI and MSI-X are enabled simultaneously".

Fixes #5228
---
 repos/os/src/app/pci_decode/main.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/repos/os/src/app/pci_decode/main.cc b/repos/os/src/app/pci_decode/main.cc
index b9ec181280..b46d299e78 100644
--- a/repos/os/src/app/pci_decode/main.cc
+++ b/repos/os/src/app/pci_decode/main.cc
@@ -145,6 +145,10 @@ bus_t Main::parse_pci_function(Bdf             bdf,
 	bool      msi_x   = cfg.msi_x_cap.constructed();
 	irq_pin_t irq_pin = cfg.read<Config::Irq_pin>();
 
+	/* disable MSI/MSI-X by default */
+	if (msi) cfg.msi_cap->write<Pci::Config::Msi_capability::Control::Enable>(0);
+	if (msi_x) cfg.msi_x_cap->write<Pci::Config::Msi_x_capability::Control::Enable>(0);
+
 	gen.node("device", [&]
 	{
 		auto string = [&] (uint64_t v) { return String<16>(Hex(v)); };