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Message-Id: <20200722001513.298315-1-jusual@redhat.com>
Date: Wed, 22 Jul 2020 02:15:13 +0200
From: Julia Suvorova <jusual@...hat.com>
To: linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Julia Suvorova <jusual@...hat.com>
Subject: [PATCH] x86/PCI: Use MMCONFIG by default for KVM guests
Scanning for PCI devices at boot takes a long time for KVM guests. It
can be reduced if KVM will handle all configuration space accesses for
non-existent devices without going to userspace [1]. But for this to
work, all accesses must go through MMCONFIG.
This change allows to use pci_mmcfg as raw_pci_ops for 64-bit KVM
guests making MMCONFIG the default access method.
[1] https://lkml.org/lkml/2020/5/14/936
Signed-off-by: Julia Suvorova <jusual@...hat.com>
---
arch/x86/pci/direct.c | 5 +++++
arch/x86/pci/mmconfig_64.c | 3 +++
2 files changed, 8 insertions(+)
diff --git a/arch/x86/pci/direct.c b/arch/x86/pci/direct.c
index a51074c55982..8ff6b65d8f48 100644
--- a/arch/x86/pci/direct.c
+++ b/arch/x86/pci/direct.c
@@ -6,6 +6,7 @@
#include <linux/pci.h>
#include <linux/init.h>
#include <linux/dmi.h>
+#include <linux/kvm_para.h>
#include <asm/pci_x86.h>
/*
@@ -264,6 +265,10 @@ void __init pci_direct_init(int type)
{
if (type == 0)
return;
+
+ if (raw_pci_ext_ops && kvm_para_available())
+ return;
+
printk(KERN_INFO "PCI: Using configuration type %d for base access\n",
type);
if (type == 1) {
diff --git a/arch/x86/pci/mmconfig_64.c b/arch/x86/pci/mmconfig_64.c
index 0c7b6e66c644..9eb772821766 100644
--- a/arch/x86/pci/mmconfig_64.c
+++ b/arch/x86/pci/mmconfig_64.c
@@ -10,6 +10,7 @@
#include <linux/init.h>
#include <linux/acpi.h>
#include <linux/bitmap.h>
+#include <linux/kvm_para.h>
#include <linux/rcupdate.h>
#include <asm/e820/api.h>
#include <asm/pci_x86.h>
@@ -122,6 +123,8 @@ int __init pci_mmcfg_arch_init(void)
}
raw_pci_ext_ops = &pci_mmcfg;
+ if (kvm_para_available())
+ raw_pci_ops = &pci_mmcfg;
return 1;
}
--
2.25.4
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