From: Paolo Bonzini <pbonzini@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>, kvm <kvm@vger.kernel.org>,
Bandan Das <bsd@redhat.com>
Subject: Re: nVMX: Shadowing of CPU_BASED_VM_EXEC_CONTROL broken
Date: Wed, 08 Oct 2014 10:47:52 +0200 [thread overview]
Message-ID: <5434FA38.5040601@redhat.com> (raw)
In-Reply-To: <5434F5F9.3030803@siemens.com>
Il 08/10/2014 10:29, Jan Kiszka ha scritto:
> Hi all,
>
> after migrating a Jailhouse VM to a newer host platform with shadow VMCS
> support I found a bug. As you may know, Jailhouse doesn't intercept
> interrupts, thus also never requests an interrupt window. Nevertheless:
>
> qemu-system-x86-5777 [001] 74970.625324: kvm_mmio: mmio write len 4 gpa 0xfebf5008 val 0x20 qemu-system-x86-5777 [001] 74970.625325: kvm_userspace_exit: reason KVM_EXIT_MMIO (6)
> qemu-system-x86-5777 [001] 74970.625330: kvm_entry: vcpu 1
> qemu-system-x86-5777 [001] 74970.625333: kvm_exit: reason PENDING_INTERRUPT rip 0xffffffff81043e54 info 0 0
> qemu-system-x86-5777 [001] 74970.625333: kvm_nested_vmexit: rip: 0xffffffff81043e54 reason: PENDING_INTERRUPT ext_inf1: 0x0000000000000000 ext_inf2: 0x0000000000000000 ext_int: 0x00000000 ext_int_err: 0x00000000
> qemu-system-x86-5777 [001] 74970.625334: kvm_nested_vmexit_inject: reason: PENDING_INTERRUPT ext_inf1: 0x0000000000000000 ext_inf2: 0x0000000000000000 ext_int: 0x00000000 ext_int_err: 0x00000000
> qemu-system-x86-5777 [001] 74970.625339: kvm_entry: vcpu 1
> qemu-system-x86-5777 [001] 74970.625341: kvm_exit: reason EPT_MISCONFIG rip 0xfffffffff0002307 info 0 0
> qemu-system-x86-5777 [001] 74970.625343: kvm_emulate_insn: 0:fffffffff0002307:8b 40 20 (prot64)
>
> And then Jailhouse crashes (which is also interesting to understand why
> - L1 host state is corrupt). Anyway, the point is that we leak
> CPU_BASED_VIRTUAL_INTR_PENDING from L0 into vmcs12. L0 sets it before
> entering L2, and then we transfer it from the hardware state to vmc12 on
> exit because that VMCS field is shadowed. The crash disappears when
> disabling VMCS shadowing.
>
> Can we simply stop shadowing CPU_BASED_VM_EXEC_CONTROL when
> CPU_BASED_VIRTUAL_INTR_PENDING is injected to L2?
The main problem is that we have a single shadowing bitmap for all
virtual machines. I cannot think of a simple solution except not
shadowing that field at all.
Paolo
next prev parent reply other threads:[~2014-10-08 8:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-08 8:29 nVMX: Shadowing of CPU_BASED_VM_EXEC_CONTROL broken Jan Kiszka
2014-10-08 8:47 ` Paolo Bonzini [this message]
2014-10-08 8:54 ` Jan Kiszka
2014-10-08 9:25 ` Wanpeng Li
2014-10-08 9:51 ` Jan Kiszka
2014-10-08 10:20 ` Paolo Bonzini
2014-10-08 10:29 ` Jan Kiszka
2014-10-08 10:34 ` Paolo Bonzini
2014-10-08 15:07 ` Jan Kiszka
2014-10-08 15:44 ` Paolo Bonzini
2014-10-08 16:07 ` Jan Kiszka
2014-10-08 23:34 ` Wanpeng Li
2014-10-08 23:58 ` Wanpeng Li
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