On 24/09/20 08:31, Huacai Chen wrote: > Hi, Sean, > > On Thu, Sep 24, 2020 at 3:00 AM Sean Christopherson > <sean.j.christopherson@xxxxxxxxx> wrote: >> >> Swap the order of hardware_enable_all() and kvm_arch_init_vm() to >> accommodate Intel's Trust Domain Extension (TDX), which needs VMX to be >> fully enabled during VM init in order to make SEAMCALLs. >> >> This also provides consistent ordering between kvm_create_vm() and >> kvm_destroy_vm() with respect to calling kvm_arch_destroy_vm() and >> hardware_disable_all(). > Do you means that hardware_enable_all() enable VMX, kvm_arch_init_vm() > enable TDX, and TDX depends on VMX enabled at first? If so, can TDX be > also enabled at hardware_enable_all()? kvm_arch_init_vm() enables TDX *for the VM*, and to do that it needs VMX instructions (specifically SEAMCALL, which is a hypervisor->"ultravisor" call). Because that action is VM-specific it cannot be done in hardware_enable_all(). Paolo > The swapping seems not affect MIPS, but I observed a fact: > kvm_arch_hardware_enable() not only be called at > hardware_enable_all(), but also be called at kvm_starting_cpu(). Even > if you swap the order, new starting CPUs are not enabled VMX before > kvm_arch_init_vm(). (Maybe I am wrong because I'm not familiar with > VMX/TDX). > > Huacai >> >> Cc: Marc Zyngier <maz@xxxxxxxxxx> >> Cc: James Morse <james.morse@xxxxxxx> >> Cc: Julien Thierry <julien.thierry.kdev@xxxxxxxxx> >> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx> >> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >> Cc: Huacai Chen <chenhc@xxxxxxxxxx> >> Cc: Aleksandar Markovic <aleksandar.qemu.devel@xxxxxxxxx> >> Cc: linux-mips@xxxxxxxxxxxxxxx >> Cc: Paul Mackerras <paulus@xxxxxxxxxx> >> Cc: kvm-ppc@xxxxxxxxxxxxxxx >> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> >> Cc: Janosch Frank <frankja@xxxxxxxxxxxxx> >> Cc: David Hildenbrand <david@xxxxxxxxxx> >> Cc: Cornelia Huck <cohuck@xxxxxxxxxx> >> Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> >> Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> >> Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx> >> Cc: Jim Mattson <jmattson@xxxxxxxxxx> >> Cc: Joerg Roedel <joro@xxxxxxxxxx> >> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> >> --- >> >> Obviously not required until the TDX series comes along, but IMO KVM >> should be consistent with respect to enabling and disabling virt support >> in hardware. >> >> Tested only on Intel hardware. Unless I missed something, this only >> affects x86, Arm and MIPS as hardware enabling is a nop for s390 and PPC. >> Arm looks safe (based on my mostly clueless reading of the code), but I >> have no idea if this will cause problem for MIPS, which is doing all kinds >> of things in hardware_enable() that I don't pretend to fully understand. >> >> virt/kvm/kvm_main.c | 16 ++++++++-------- >> 1 file changed, 8 insertions(+), 8 deletions(-) >> >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index cf88233b819a..58fa19bcfc90 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -766,7 +766,7 @@ static struct kvm *kvm_create_vm(unsigned long type) >> struct kvm_memslots *slots = kvm_alloc_memslots(); >> >> if (!slots) >> - goto out_err_no_arch_destroy_vm; >> + goto out_err_no_disable; >> /* Generations must be different for each address space. */ >> slots->generation = i; >> rcu_assign_pointer(kvm->memslots[i], slots); >> @@ -776,19 +776,19 @@ static struct kvm *kvm_create_vm(unsigned long type) >> rcu_assign_pointer(kvm->buses[i], >> kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL_ACCOUNT)); >> if (!kvm->buses[i]) >> - goto out_err_no_arch_destroy_vm; >> + goto out_err_no_disable; >> } >> >> kvm->max_halt_poll_ns = halt_poll_ns; >> >> - r = kvm_arch_init_vm(kvm, type); >> - if (r) >> - goto out_err_no_arch_destroy_vm; >> - >> r = hardware_enable_all(); >> if (r) >> goto out_err_no_disable; >> >> + r = kvm_arch_init_vm(kvm, type); >> + if (r) >> + goto out_err_no_arch_destroy_vm; >> + >> #ifdef CONFIG_HAVE_KVM_IRQFD >> INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list); >> #endif >> @@ -815,10 +815,10 @@ static struct kvm *kvm_create_vm(unsigned long type) >> mmu_notifier_unregister(&kvm->mmu_notifier, current->mm); >> #endif >> out_err_no_mmu_notifier: >> - hardware_disable_all(); >> -out_err_no_disable: >> kvm_arch_destroy_vm(kvm); >> out_err_no_arch_destroy_vm: >> + hardware_disable_all(); >> +out_err_no_disable: >> WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count)); >> for (i = 0; i < KVM_NR_BUSES; i++) >> kfree(kvm_get_bus(kvm, i)); >> -- >> 2.28.0 >> >
