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@xxxxxxxxxx> --- 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
