[PATCH AUTOSEL 4.9 14/27] x86/apic: Fix arch_dynirq_lower_bound() bug for DT enabled machines

From: Sasha Levin
Date: Wed Sep 04 2019 - 12:02:50 EST

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

[ Upstream commit 3e5bedc2c258341702ddffbd7688c5e6eb01eafa ]

Rahul Tanwar reported the following bug on DT systems:

> 'ioapic_dynirq_base' contains the virtual IRQ base number. Presently, it is
> updated to the end of hardware IRQ numbers but this is done only when IOAPIC
> configuration type is IOAPIC_DOMAIN_LEGACY or IOAPIC_DOMAIN_STRICT. There is
> a third type IOAPIC_DOMAIN_DYNAMIC which applies when IOAPIC configuration
> comes from devicetree.
> See dtb_add_ioapic() in arch/x86/kernel/devicetree.c
> In case of IOAPIC_DOMAIN_DYNAMIC (DT/OF based system), 'ioapic_dynirq_base'
> remains to zero initialized value. This means that for OF based systems,
> virtual IRQ base will get set to zero.

Such systems will very likely not even boot.

For DT enabled machines ioapic_dynirq_base is irrelevant and not
updated, so simply map the IRQ base 1:1 instead.

Reported-by: Rahul Tanwar <rahul.tanwar@xxxxxxxxxxxxxxx>
Tested-by: Rahul Tanwar <rahul.tanwar@xxxxxxxxxxxxxxx>
Tested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: alan@xxxxxxxxxxxxxxx
Cc: bp@xxxxxxxxx
Cc: cheol.yong.kim@xxxxxxxxx
Cc: qi-ming.wu@xxxxxxxxx
Cc: rahul.tanwar@xxxxxxxxx
Cc: rppt@xxxxxxxxxxxxx
Cc: tony.luck@xxxxxxxxx
Link: http://lkml.kernel.org/r/20190821081330.1187-1-rahul.tanwar@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
arch/x86/kernel/apic/io_apic.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index d34629d70421f..09dd95cabfc28 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2346,7 +2346,13 @@ unsigned int arch_dynirq_lower_bound(unsigned int from)
* dmar_alloc_hwirq() may be called before setup_IO_APIC(), so use
* gsi_top if ioapic_dynirq_base hasn't been initialized yet.
- return ioapic_initialized ? ioapic_dynirq_base : gsi_top;
+ if (!ioapic_initialized)
+ return gsi_top;
+ /*
+ * For DT enabled machines ioapic_dynirq_base is irrelevant and not
+ * updated. So simply return @from if ioapic_dynirq_base == 0.
+ */
+ return ioapic_dynirq_base ? : from;

#ifdef CONFIG_X86_32