linux-kernel - [PATCH] powerpc/chrp: Revert "Move PHB discovery" and "Make hydra

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Message-Id: <20210716221159.3587039-1-linux@roeck-us.net>
Date:   Fri, 16 Jul 2021 15:11:59 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>,
        Oliver O'Halloran <oohall@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] powerpc/chrp: Revert "Move PHB discovery" and "Make hydra_init() static"

This patch reverts commit 407d418f2fd4 ("powerpc/chrp: Move PHB
discovery") and commit 9634afa67bfd ("powerpc/chrp: Make hydra_init()
static").

Running the upstream kernel on Qemu's brand new "pegasos2" emulation
results in a variety of backtraces such as

Kernel attempted to write user page (a1) - exploit attempt? (uid: 0)
------------[ cut here ]------------
Bug: Write fault blocked by KUAP!
WARNING: CPU: 0 PID: 0 at arch/powerpc/mm/fault.c:230 do_page_fault+0x4f4/0x920
CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.2 #40
NIP:  c0021824 LR: c0021824 CTR: 00000000
REGS: c1085d50 TRAP: 0700   Not tainted  (5.13.2)
MSR:  00021032 <ME,IR,DR,RI>  CR: 24042254  XER: 00000000

GPR00: c0021824 c1085e10 c0f8c520 00000021 3fffefff c1085c60 c1085c58 00000000
GPR08: 00001032 00000000 00000000 c0ffb3ec 44042254 00000000 00000000 00000004
GPR16: 00000000 ffffffff 000000c4 000000d0 0188c6e0 01006000 00000001 40b14000
GPR24: c0ec000c 00000300 02000000 00000000 42000000 000000a1 00000000 c1085e60
NIP [c0021824] do_page_fault+0x4f4/0x920
LR [c0021824] do_page_fault+0x4f4/0x920
Call Trace:
[c1085e10] [c0021824] do_page_fault+0x4f4/0x920 (unreliable)
[c1085e50] [c0004254] DataAccess_virt+0xd4/0xe4

and the system fails to boot. Bisect points to commit 407d418f2fd4
("powerpc/chrp: Move PHB discovery"). Reverting this patch together with
commit 9634afa67bfd ("powerpc/chrp: Make hydra_init() static") fixes
the problem.

Cc: Oliver O'Halloran <oohall@...il.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Fixes: 407d418f2fd4 ("powerpc/chrp: Move PHB discovery")
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 arch/powerpc/include/asm/hydra.h    |  2 ++
 arch/powerpc/platforms/chrp/pci.c   | 11 ++---------
 arch/powerpc/platforms/chrp/setup.c | 12 +++++++++++-
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/hydra.h b/arch/powerpc/include/asm/hydra.h
index d024447283a0..ae02eb53d6ef 100644
--- a/arch/powerpc/include/asm/hydra.h
+++ b/arch/powerpc/include/asm/hydra.h
@@ -94,6 +94,8 @@ extern volatile struct Hydra __iomem *Hydra;
 #define HYDRA_INT_EXT7		18	/* Power Off Request */
 #define HYDRA_INT_SPARE		19
 
+extern int hydra_init(void);
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASMPPC_HYDRA_H */
diff --git a/arch/powerpc/platforms/chrp/pci.c b/arch/powerpc/platforms/chrp/pci.c
index 76e6256cb0a7..b2c2bf35b76c 100644
--- a/arch/powerpc/platforms/chrp/pci.c
+++ b/arch/powerpc/platforms/chrp/pci.c
@@ -131,7 +131,8 @@ static struct pci_ops rtas_pci_ops =
 
 volatile struct Hydra __iomem *Hydra = NULL;
 
-static int __init hydra_init(void)
+int __init
+hydra_init(void)
 {
 	struct device_node *np;
 	struct resource r;
@@ -313,14 +314,6 @@ chrp_find_bridges(void)
 		}
 	}
 	of_node_put(root);
-
-	/*
-	 *  "Temporary" fixes for PCI devices.
-	 *  -- Geert
-	 */
-	hydra_init();		/* Mac I/O */
-
-	pci_create_OF_bus_map();
 }
 
 /* SL82C105 IDE Control/Status Register */
diff --git a/arch/powerpc/platforms/chrp/setup.c b/arch/powerpc/platforms/chrp/setup.c
index 3cfc382841e5..c45435aa5e36 100644
--- a/arch/powerpc/platforms/chrp/setup.c
+++ b/arch/powerpc/platforms/chrp/setup.c
@@ -334,11 +334,22 @@ static void __init chrp_setup_arch(void)
 	/* On pegasos, enable the L2 cache if not already done by OF */
 	pegasos_set_l2cr();
 
+	/* Lookup PCI host bridges */
+	chrp_find_bridges();
+
+	/*
+	 *  Temporary fixes for PCI devices.
+	 *  -- Geert
+	 */
+	hydra_init();		/* Mac I/O */
+
 	/*
 	 *  Fix the Super I/O configuration
 	 */
 	sio_init();
 
+	pci_create_OF_bus_map();
+
 	/*
 	 * Print the banner, then scroll down so boot progress
 	 * can be printed.  -- Cort
@@ -571,7 +582,6 @@ define_machine(chrp) {
 	.name			= "CHRP",
 	.probe			= chrp_probe,
 	.setup_arch		= chrp_setup_arch,
-	.discover_phbs		= chrp_find_bridges,
 	.init			= chrp_init2,
 	.show_cpuinfo		= chrp_show_cpuinfo,
 	.init_IRQ		= chrp_init_IRQ,
-- 
2.25.1