diff options
| author | Saurabh Sengar <ssengar@linux.microsoft.com> | 2023-03-28 00:30:04 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2023-04-12 17:45:50 +0200 |
| commit | 5af507bef93c09a94fb8f058213b489178f4cbe5 (patch) | |
| tree | 4b8028b10f38224167c67018ae0fb7142a8f9661 /arch/x86/kernel | |
| parent | f96fb2df3eb31ede1b34b0521560967310267750 (diff) | |
x86/ioapic: Don't return 0 from arch_dynirq_lower_bound()
arch_dynirq_lower_bound() is invoked by the core interrupt code to
retrieve the lowest possible Linux interrupt number for dynamically
allocated interrupts like MSI.
The x86 implementation uses this to exclude the IO/APIC GSI space.
This works correctly as long as there is an IO/APIC registered, but
returns 0 if not. This has been observed in VMs where the BIOS does
not advertise an IO/APIC.
0 is an invalid interrupt number except for the legacy timer interrupt
on x86. The return value is unchecked in the core code, so it ends up
to allocate interrupt number 0 which is subsequently considered to be
invalid by the caller, e.g. the MSI allocation code.
The function has already a check for 0 in the case that an IO/APIC is
registered, as ioapic_dynirq_base is 0 in case of device tree setups.
Consolidate this and zero check for both ioapic_dynirq_base and gsi_top,
which is used in the case that no IO/APIC is registered.
Fixes: 3e5bedc2c258 ("x86/apic: Fix arch_dynirq_lower_bound() bug for DT enabled machines")
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1679988604-20308-1-git-send-email-ssengar@linux.microsoft.com
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/apic/io_apic.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 1f83b052bb74..f980b38b0227 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2477,17 +2477,21 @@ static int io_apic_get_redir_entries(int ioapic) unsigned int arch_dynirq_lower_bound(unsigned int from) { + unsigned int ret; + /* * dmar_alloc_hwirq() may be called before setup_IO_APIC(), so use * gsi_top if ioapic_dynirq_base hasn't been initialized yet. */ - if (!ioapic_initialized) - return gsi_top; + ret = ioapic_dynirq_base ? : gsi_top; + /* - * For DT enabled machines ioapic_dynirq_base is irrelevant and not - * updated. So simply return @from if ioapic_dynirq_base == 0. + * For DT enabled machines ioapic_dynirq_base is irrelevant and + * always 0. gsi_top can be 0 if there is no IO/APIC registered. + * 0 is an invalid interrupt number for dynamic allocations. Return + * @from instead. */ - return ioapic_dynirq_base ? : from; + return ret ? : from; } #ifdef CONFIG_X86_32 |