Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] KVM: vmx: hyper-v: don't pass EPT configuration info to vmx_hv_remote_flush_tlb() | Date | Thu, 11 Oct 2018 15:00:47 +0200 |
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Tianyu Lan <lantianyu1986@gmail.com> writes:
> On Thu, Oct 11, 2018 at 8:18 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote: >> >> Tianyu Lan <lantianyu1986@gmail.com> writes: >> >> > On Thu, Oct 11, 2018 at 6:32 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote: >> >> >> >> I'm observing random crashes in multi-vCPU L2 guests running on KVM on >> >> Hyper-V. I bisected the issue to the commit 877ad952be3d ("KVM: vmx: Add >> >> tlb_remote_flush callback support"). Hyper-V TLFS states: >> >> >> >> "AddressSpace specifies an address space ID (an EPT PML4 table pointer)" >> >> >> >> So apparently, Hyper-V doesn't expect us to pass naked EPTP, only PML4 >> >> pointer should be used. Strip off EPT configuration information before >> >> calling into vmx_hv_remote_flush_tlb(). >> > >> > Hi Vitaly: >> > : Thanks to fix this. Sorry, I didn't meet the issue.. >> > I think we may just store EPT PML4 table pointer without EPT >> > configuration information >> > in the ept_pointer field for this case. >> > >> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> > index 619307b3e6bb..e316058b41a6 100644 >> > --- a/arch/x86/kvm/vmx.c >> > +++ b/arch/x86/kvm/vmx.c >> > @@ -5379,7 +5379,7 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, >> > unsigned long cr3) >> > >> > if (kvm_x86_ops->tlb_remote_flush) { >> > spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock); >> > - to_vmx(vcpu)->ept_pointer = eptp; >> > + to_vmx(vcpu)->ept_pointer = cr3; >> >> True, we can do that (and I even had a version of my patch doing so) >> but 'ept_pointer' will likely need to be renamed as it's not obvious >> why vcpu->ept_pointer != eptp. >> > > Yes. that need to rename ept_pointer. >
Honestly, I would prefer to keep more information cached, e.g. if someone needs EPT configuration data later he can easily get it from ept_pointer and by putting raw cr3 there we'll just keep less.
But I don't have a strong opinion, I'll leave it up to the maintainers to tell us how to proceed)
>> Alternatively, we can filter lower 12 bits out in >> hyperv_flush_guest_mapping() but I would rename 'as' parameter to eptp >> then. > > OK. I got it. Thanks.
-- Vitaly
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