Liran Alon <liran.alon@xxxxxxxxxx> writes:
>> On 26 Mar 2019, at 15:07, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
>>
>> Commit 5bea5123cbf0 ("KVM: VMX: check nested state and CR4.VMXE against
>> SMM") introduced a check to vmx_set_cr4() forbidding to set VMXE from SMM.
>> The check is correct, however, there is a special case when RSM is called
>> to leave SMM: rsm_enter_protected_mode() is called with HF_SMM_MASK still
>> set and in case VMXE was set before entering SMM we're failing to return.
>>
>> Resolve the issue by temporary dropping HF_SMM_MASK around set_cr4() calls
>> when ops->set_cr() is called from RSM.
>>
>> Reported-by: Jon Doron <arilou@xxxxxxxxx>
>> Suggested-by: Liran Alon <liran.alon@xxxxxxxxxx>
>> Fixes: 5bea5123cbf0 ("KVM: VMX: check nested state and CR4.VMXE against SMM")
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>
> Patch looks good to me.
> Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>
Thanks!
>
>> ---
>> - Instread of putting the temporary HF_SMM_MASK drop to
>> rsm_enter_protected_mode() (as was suggested by Liran), move it to
>> emulator_set_cr() modifying its interface. emulate.c seems to be
>> vcpu-specifics-free at this moment, we may want to keep it this way.
>> - It seems that Hyper-V+UEFI on KVM is still broken, I'm observing sporadic
>> hangs even with this patch. These hangs, however, seem to be unrelated to
>> rsm.
>
> Feel free to share details on these hangs ;)
>
You've asked for it)
The immediate issue I'm observing is some sort of a lockup which is easy
to trigger with e.g. "-usb -device usb-tablet" on Qemu command line; it
seems we get too many interrupts and combined with preemtion timer for
L2 we're not making any progress:
kvm_userspace_exit: reason KVM_EXIT_IOAPIC_EOI (26)
kvm_set_irq: gsi 18 level 1 source 0
kvm_msi_set_irq: dst 0 vec 177 (Fixed|physical|level)
kvm_apic_accept_irq: apicid 0 vec 177 (Fixed|edge)
kvm_fpu: load
kvm_entry: vcpu 0
kvm_exit: reason VMRESUME rip 0xfffff80000848115 info 0 0
kvm_entry: vcpu 0
kvm_exit: reason PREEMPTION_TIMER rip 0xfffff800f4448e01 info 0 0
kvm_nested_vmexit: rip fffff800f4448e01 reason PREEMPTION_TIMER info1 0 info2 0 int_info 0 int_info_err 0
kvm_nested_vmexit_inject: reason EXTERNAL_INTERRUPT info1 0 info2 0 int_info 800000b1 int_info_err 0
kvm_entry: vcpu 0
kvm_exit: reason APIC_ACCESS rip 0xfffff8000081fe11 info 10b0 0
kvm_apic: apic_write APIC_EOI = 0x0
kvm_eoi: apicid 0 vector 177
kvm_fpu: unload
kvm_userspace_exit: reason KVM_EXIT_IOAPIC_EOI (26)
...
(and the pattern repeats)
Maybe it is a usb-only/Qemu-only problem, maybe not.
--
Vitaly
