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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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2dea4c84bc
This issue just appeared in kvm-84 when running on 2.6.28.7 (x86-64) with PREEMPT enabled. We're getting syslog warnings like this many (but not all) times qemu tells KVM to run the VCPU: BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-x86/28938 caller is kvm_arch_vcpu_ioctl_run+0x5d1/0xc70 [kvm] Pid: 28938, comm: qemu-system-x86 2.6.28.7-mtyrel-64bit Call Trace: debug_smp_processor_id+0xf7/0x100 kvm_arch_vcpu_ioctl_run+0x5d1/0xc70 [kvm] ? __wake_up+0x4e/0x70 ? wake_futex+0x27/0x40 kvm_vcpu_ioctl+0x2e9/0x5a0 [kvm] enqueue_hrtimer+0x8a/0x110 _spin_unlock_irqrestore+0x27/0x50 vfs_ioctl+0x31/0xa0 do_vfs_ioctl+0x74/0x480 sys_futex+0xb4/0x140 sys_ioctl+0x99/0xa0 system_call_fastpath+0x16/0x1b As it turns out, the call trace is messed up due to gcc's inlining, but I isolated the problem anyway: kvm_write_guest_time() is being used in a non-thread-safe manner on preemptable kernels. Basically kvm_write_guest_time()'s body needs to be surrounded by preempt_disable() and preempt_enable(), since the kernel won't let us query any per-CPU data (indirectly using smp_processor_id()) without preemption disabled. The attached patch fixes this issue by disabling preemption inside kvm_write_guest_time(). [marcelo: surround only __get_cpu_var calls since the warning is harmless] Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com> |
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| .. | ||
| i8254.c | ||
| i8254.h | ||
| i8259.c | ||
| irq.c | ||
| irq.h | ||
| Kconfig | ||
| kvm_cache_regs.h | ||
| kvm_svm.h | ||
| lapic.c | ||
| lapic.h | ||
| Makefile | ||
| mmu.c | ||
| mmu.h | ||
| paging_tmpl.h | ||
| svm.c | ||
| tss.h | ||
| vmx.c | ||
| x86_emulate.c | ||
| x86.c | ||
| x86.h | ||