linux-kernel - [PATCH] x86/jailhouse: Respect pci=lastbus command line settings

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Date:   Fri, 19 Jan 2018 11:06:30 +0100
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     x86 <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>
Cc:     Jailhouse <jailhouse-dev@...glegroups.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/jailhouse: Respect pci=lastbus command line settings

Limiting the scan width to the known last bus via the command line can
accelerate the boot noteworthy.

Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
 arch/x86/kernel/jailhouse.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c
index 2b7ebbe9043d..b68fd895235a 100644
--- a/arch/x86/kernel/jailhouse.c
+++ b/arch/x86/kernel/jailhouse.c
@@ -119,8 +119,10 @@ static int __init jailhouse_pci_arch_init(void)
 	/*
 	 * There are no bridges on the virtual PCI root bus under Jailhouse,
 	 * thus no other way to discover all devices than a full scan.
+	 * Respect any overrides via the command line, though.
 	 */
-	pcibios_last_bus = 0xff;
+	if (pcibios_last_bus < 0)
+		pcibios_last_bus = 0xff;
 
 	return 0;
 }