> -----Original Message----- > From: zhangfei.gao@xxxxxxxxxxx [mailto:zhangfei.gao@xxxxxxxxxxx] > Sent: 13 June 2022 07:56 > To: paulmck@xxxxxxxxxx > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>; Zhangfei Gao > <zhangfei.gao@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; > rcu@xxxxxxxxxxxxxxx; Lai Jiangshan <jiangshanlai@xxxxxxxxx>; Josh Triplett > <josh@xxxxxxxxxxxxxxxx>; Mathieu Desnoyers > <mathieu.desnoyers@xxxxxxxxxxxx>; Matthew Wilcox <willy@xxxxxxxxxxxxx>; > Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>; > mtosatti@xxxxxxxxxx; Auger Eric <eric.auger@xxxxxxxxxx> > Subject: Re: Commit 282d8998e997 (srcu: Prevent expedited GPs and > blocking readers from consuming CPU) cause qemu boot slow > > By the way, the issue should be only related with qemu apci. not related > with rmr feature > Test with: https://github.com/qemu/qemu/tree/stable-6.1 > > Looks it caused by too many kvm_region_add & kvm_region_del if > acpi=force, Based on the setup I have, I think it has nothing to do with Guest kernel booting with ACPI per se(ie, acpi=force in Qemu kernel cmd line). It is more to do with Qemu having the "-bios QEMU_EFI.fd" which sets up pflash devices resulting in large number of pflash read/write calls(before Guest kernel even boots) which in turn seems to be triggering the below kvm_region_add/del calls. Thanks, Shameer > If no acpi, no print kvm_region_add/del (1000 times print once) > > If with acpi=force, > During qemu boot > kvm_region_add region_add = 1000 > kvm_region_del region_del = 1000 > kvm_region_add region_add = 2000 > kvm_region_del region_del = 2000 > kvm_region_add region_add = 3000 > kvm_region_del region_del = 3000 > kvm_region_add region_add = 4000 > kvm_region_del region_del = 4000 > kvm_region_add region_add = 5000 > kvm_region_del region_del = 5000 > kvm_region_add region_add = 6000 > kvm_region_del region_del = 6000 > > kvm_region_add/kvm_region_del -> > kvm_set_phys_mem-> > kvm_set_user_memory_region-> > kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem) > > [ 361.094493] __synchronize_srcu loop=9000 > [ 361.094501] Call trace: > [ 361.094502] dump_backtrace+0xe4/0xf0 > [ 361.094505] show_stack+0x20/0x70 > [ 361.094507] dump_stack_lvl+0x8c/0xb8 > [ 361.094509] dump_stack+0x18/0x34 > [ 361.094511] __synchronize_srcu+0x120/0x128 > [ 361.094514] synchronize_srcu_expedited+0x2c/0x40 > [ 361.094515] kvm_swap_active_memslots+0x130/0x198 > [ 361.094519] kvm_activate_memslot+0x40/0x68 > [ 361.094520] kvm_set_memslot+0x2f8/0x3b0 > [ 361.094523] __kvm_set_memory_region+0x2e4/0x438 > [ 361.094524] kvm_set_memory_region+0x78/0xb8 > [ 361.094526] kvm_vm_ioctl+0x5a0/0x13e0 > [ 361.094528] __arm64_sys_ioctl+0xb0/0xf8 > [ 361.094530] invoke_syscall+0x4c/0x110 > [ 361.094533] el0_svc_common.constprop.0+0x68/0x128 > [ 361.094536] do_el0_svc+0x34/0xc0 > [ 361.094538] el0_svc+0x30/0x98 > [ 361.094541] el0t_64_sync_handler+0xb8/0xc0 > [ 361.094544] el0t_64_sync+0x18c/0x190 > [ 363.942817] kvm_set_memory_region loop=6000 > >
