From: Saurabh Sengar ssengar@linux.microsoft.com
[ Upstream commit 5af507bef93c09a94fb8f058213b489178f4cbe5 ]
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.mi... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/apic/io_apic.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index a868b76cd3d42..efa87b6bb1cde 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2480,17 +2480,21 @@ 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