Sorry for the late response > -----Original Message----- > From: Avi Kivity [mailto:avi@xxxxxxxxxx] > Sent: Friday, September 07, 2012 12:02 AM > To: Li, Jiongxi > Cc: kvm@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/5]KVM: x86, apicv: add APICv register virtualization > support > > On 09/05/2012 08:41 AM, Li, Jiongxi wrote: > > - APIC read doesn't cause VM-Exit > > - APIC write becomes trap-like > > > > > > +/* emulate APIC access in a trap manner */ int > > +kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset) { > > + u32 val; > > + > > + /* hw has done the conditional check and inst decode */ > > + offset &= 0xff0; > > + if ((offset != APIC_EOI) && > > + apic_reg_read(vcpu->arch.apic, offset, 4, &val)) > > + return 1; > > TMICT is a write-only register IIRC. > I haven't seen TMICT write-only in SDM. Also in there is ' apic_get_reg(apci,APIC_TMICT)' call in 'apic_get_tmcct' function. > > + > > + /* TODO: optimize to just emulate side effect w/o one more write */ > > + return apic_reg_write(vcpu->arch.apic, offset, val); > > val may be uninitialized here. > Can you elaborate that? For APIC_EOI, there is no need to use val. For apic_reg_read fails case, it will return before apic_reg_write > > +} > > +EXPORT_SYMBOL_GPL(kvm_apic_write_nodecode); > > + > > void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu) { > > > > +static bool __read_mostly enable_apicv_reg = 0; > > Enable by default. > > > +module_param(enable_apicv_reg, bool, S_IRUGO); > > Let's have one module parameter for all related features, called apicv. > So modeprobe kvm-intel apicv=0 disables it. Ok, We will change that > > > > > +static int handle_apic_write(struct kvm_vcpu *vcpu) { > > + unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION); > > + u32 offset = exit_qualification & 0xfff; > > + > > + /* APIC-write VM exit is trap-like and thus no need to adjust IP */ > > + return kvm_apic_write_nodecode(vcpu, offset) == 0; } > > Return 1 here means exit to userspace. This will go crazy. > > You need to return 0 always. If this is an msr write to a read-only register, you > need to inject a #GP (IIRC). Oks. > > > > -- > error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
