linux-kernel - Re: [PATCHv2 4/4] arm64: add host pv-vcpu-state support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJWu+oqCyj3H0=1KNo3c+crdcktYinFoTQJ5jHgU8gjeF4d2yA@mail.gmail.com>
Date:   Tue, 20 Jul 2021 14:44:53 -0400
From:   Joel Fernandes <joelaf@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Will Deacon <will@...nel.org>,
        Suleiman Souhlal <suleiman@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCHv2 4/4] arm64: add host pv-vcpu-state support

On Mon, Jul 12, 2021 at 12:24 PM Marc Zyngier <maz@...nel.org> wrote:
>
[...]
> > +}
> > +
> > +static inline bool
> > +kvm_arm_is_vcpu_state_enabled(struct kvm_vcpu_arch *vcpu_arch)
> > +{
> > +     return (vcpu_arch->vcpu_state.base != GPA_INVALID);
> > +}
> > +
> > +void kvm_update_vcpu_preempted(struct kvm_vcpu *vcpu, bool preempted);
> > +
> >  void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
> >
> >  struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
> > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> > index 989bb5dad2c8..2a3ee82c6d90 100644
> > --- a/arch/arm64/kvm/Makefile
> > +++ b/arch/arm64/kvm/Makefile
> > @@ -12,7 +12,8 @@ obj-$(CONFIG_KVM) += hyp/
> >
> >  kvm-y := $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o \
> >        $(KVM)/vfio.o $(KVM)/irqchip.o $(KVM)/binary_stats.o \
> > -      arm.o mmu.o mmio.o psci.o perf.o hypercalls.o pvtime.o \
> > +      arm.o mmu.o mmio.o psci.o perf.o hypercalls.o \
> > +      pvtime.o pv-vcpu-state.o \
> >        inject_fault.o va_layout.o handle_exit.o \
> >        guest.o debug.o reset.o sys_regs.o \
> >        vgic-sys-reg-v3.o fpsimd.o pmu.o \
> > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> > index e9a2b8f27792..43e995c9fddb 100644
> > --- a/arch/arm64/kvm/arm.c
> > +++ b/arch/arm64/kvm/arm.c
> > @@ -332,6 +332,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> >       kvm_arm_reset_debug_ptr(vcpu);
> >
> >       kvm_arm_pvtime_vcpu_init(&vcpu->arch);
> > +     kvm_arm_vcpu_state_init(&vcpu->arch);
> >
> >       vcpu->arch.hw_mmu = &vcpu->kvm->arch.mmu;
> >
> > @@ -429,10 +430,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> >       if (vcpu_has_ptrauth(vcpu))
> >               vcpu_ptrauth_disable(vcpu);
> >       kvm_arch_vcpu_load_debug_state_flags(vcpu);
> > +     kvm_update_vcpu_preempted(vcpu, false);
> >  }
> >
> >  void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> >  {
> > +     kvm_update_vcpu_preempted(vcpu, true);
>
> This doesn't look right. With this, you are now telling the guest that
> a vcpu that is blocked on WFI is preempted. This really isn't the
> case, as it has voluntarily entered a low-power mode while waiting for
> an interrupt. Indeed, the vcpu isn't running. A physical CPU wouldn't
> be running either.

Can that be cured by just checking vcpu->preempted before calling
kvm_update_vcpu_preempted() ?

- Joel