On Wed, Jul 22, 2020 at 12:47 PM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote: > Julia Suvorova <jusual@xxxxxxxxxx> writes: > > 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. I'm not sure it won't break anything. > > [1] https://lkml.org/lkml/2020/5/14/936 use Link: tag and better to use lore.kernel.org. > This implies mmconfig access method is always functional (when present) > for all KVM guests, regardless of hypervisor version/which KVM userspace > is is use/... In case the assumption is true the patch looks good (to > me) but in case it isn't or if we think that more control over this > is needed we may want to introduce a PV feature bit for KVM. > > Also, I'm thinking about moving this to arch/x86/kernel/kvm.c: we can > override x86_init.pci.arch_init and reassign raw_pci_ops after doing > pci_arch_init(). % git grep -n -w x86_init.pci.arch_init -- arch/x86/ arch/x86/hyperv/hv_init.c:400: x86_init.pci.arch_init = hv_pci_init; arch/x86/kernel/apic/apic_numachip.c:203: x86_init.pci.arch_init = pci_numachip_init; arch/x86/kernel/jailhouse.c:207: x86_init.pci.arch_init = jailhouse_pci_arch_init; arch/x86/pci/init.c:20: if (x86_init.pci.arch_init && !x86_init.pci.arch_init()) arch/x86/platform/intel-mid/intel-mid.c:172: x86_init.pci.arch_init = intel_mid_pci_init; arch/x86/platform/olpc/olpc.c:309: x86_init.pci.arch_init = pci_olpc_init; arch/x86/xen/enlighten_pv.c:1411: x86_init.pci.arch_init = pci_xen_init; Are you going to update all these? Or how this is supposed to work (I may be missing something)? -- With Best Regards, Andy Shevchenko
