linux-kernel - [PATCH] x86/ioapic: Don't return 0 as valid virq

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Date:   Thu,  2 Mar 2023 11:34:46 -0800
From:   Saurabh Sengar <ssengar@...ux.microsoft.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        johan+linaro@...nel.org, isaku.yamahata@...el.com,
        mikelley@...rosoft.com, linux-kernel@...r.kernel.org
Subject: [PATCH] x86/ioapic: Don't return 0 as valid virq

Zero is invalid virq and should't be returned as a valid value for
lower irq bound. If IO-APIC and gsi_top are not initialized return
the 'from' value as virq.

Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
---
 arch/x86/kernel/apic/io_apic.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a868b76cd3d4..000cc6159b8b 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2483,9 +2483,11 @@ 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.
+	 *
+	 * Incase gsi_top is also not initialized return @from.
 	 */
 	if (!ioapic_initialized)
-		return gsi_top;
+		return gsi_top ? : from;
 	/*
 	 * For DT enabled machines ioapic_dynirq_base is irrelevant and not
 	 * updated. So simply return @from if ioapic_dynirq_base == 0.
-- 
2.34.1