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authorSaurabh Sengar <ssengar@linux.microsoft.com>2023-03-28 00:30:04 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-05-17 11:35:39 +0200
commit442470948c0401c8b56bec51353fa0efc7b67b73 (patch)
tree71d2797ee02b78425a2198ee2bad034a4ed788d5 /arch/x86/kernel/apic
parent824683dbec234a01bd49a0589ee3323594a6f4cf (diff)
x86/ioapic: Don't return 0 from arch_dynirq_lower_bound()
[ 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.microsoft.com Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch/x86/kernel/apic')
-rw-r--r--arch/x86/kernel/apic/io_apic.c14
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 1622cff009c9..e4d63392c619 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2455,17 +2455,21 @@ 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