From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 5/8] KVM: x86: use MDA for interrupt matching Date: Fri, 30 Jan 2015 10:03:49 +0100 Message-ID: <54CB48F5.9060503@redhat.com> References: <1422568135-28402-1-git-send-email-rkrcmar@redhat.com> <1422568135-28402-6-git-send-email-rkrcmar@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm@vger.kernel.org, Nadav Amit , Gleb Natapov To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1422568135-28402-6-git-send-email-rkrcmar@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 29/01/2015 22:48, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote: > In mixed modes, we musn't deliver xAPIC IPIs like x2APIC and vice ver= sa. > Instead of preserving the information in apic_send_ipi(), we regain i= t > by converting all destinations into correct APIC MDA in the slow path= =2E > This allows easier reasoning about subsequent matching. >=20 > kvm_apic_broadcast() had an interesting design decision: > it didn't consider IOxAPIC 0xff as broadcast in x2APIC mode ... > everything worked because IOxAPIC can't set that in physical mode and > logical mode considered it as a message for first 8 VCPUs. > This patch interprets IOxAPIC 0xff as x2APIC broadcast. >=20 > Signed-off-by: Radim Kr=C4=8Dm=C3=A1=C5=99 > --- > arch/x86/kvm/lapic.c | 40 +++++++++++++++++++++++++++++++++------- > 1 file changed, 33 insertions(+), 7 deletions(-) >=20 > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index aae043f38548..871ce6a2485b 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -581,15 +581,24 @@ static void apic_set_tpr(struct kvm_lapic *apic= , u32 tpr) > apic_update_ppr(apic); > } > =20 > -static bool kvm_apic_broadcast(struct kvm_lapic *apic, u32 dest) > +static bool kvm_apic_broadcast(struct kvm_lapic *apic, u32 mda) > { > - return dest =3D=3D (apic_x2apic_mode(apic) ? > - X2APIC_BROADCAST : APIC_BROADCAST); > + if (apic_x2apic_mode(apic)) > + return mda =3D=3D X2APIC_BROADCAST; > + > + /* XXX: verify that xAPIC accepts x2APIC broadcast */ > + return GET_APIC_DEST_FIELD(mda) =3D=3D APIC_BROADCAST; > } > =20 > -static bool kvm_apic_match_physical_addr(struct kvm_lapic *apic, u32= dest) > +static bool kvm_apic_match_physical_addr(struct kvm_lapic *apic, u32= mda) > { > - return kvm_apic_id(apic) =3D=3D dest || kvm_apic_broadcast(apic, de= st); > + if (kvm_apic_broadcast(apic, mda)) > + return true; > + > + if (apic_x2apic_mode(apic)) > + return mda =3D=3D kvm_apic_id(apic); > + > + return mda =3D=3D SET_APIC_DEST_FIELD(kvm_apic_id(apic)); > } > =20 > static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 = mda) > @@ -606,6 +615,7 @@ static bool kvm_apic_match_logical_addr(struct kv= m_lapic *apic, u32 mda) > && (logical_id & mda & 0xffff); > =20 > logical_id =3D GET_APIC_LOGICAL_ID(logical_id); > + mda =3D GET_APIC_DEST_FIELD(mda); > =20 > switch (kvm_apic_get_reg(apic, APIC_DFR)) { > case APIC_DFR_FLAT: > @@ -620,10 +630,26 @@ static bool kvm_apic_match_logical_addr(struct = kvm_lapic *apic, u32 mda) > } > } > =20 > +/* KVM APIC implementation has two quirks > + * - dest always begins at 0 while xAPIC MDA has offset 24, > + * - IOxAPIC messages have to be delivered (directly) to x2APIC. > + */ > +static u32 > +kvm_apic_mda(unsigned int dest, struct kvm_lapic *ipi, bool x2apic_d= est) Please pass two struct kvm_lapic, so that you can write bool ipi =3D source !=3D NULL; bool x2apic_mda =3D apic_x2apic_mode(ipi ? source : dest); Looks a little nicer to me at least. > +{ > + bool x2apic_mda =3D ipi ? apic_x2apic_mode(ipi) : x2apic_dest; > + > + if (!ipi && dest =3D=3D APIC_BROADCAST) > + dest =3D X2APIC_BROADCAST; This works, but it is not super-clear that you are shifting left by 24 here, and right in kvm_apic_broadcast(). What if you just make it if (!ipi && dest =3D=3D APIC_BROADCAST && x2apic_mda) return X2APIC_BROADCAST. ? Paolo > + > + return x2apic_mda ? dest : SET_APIC_DEST_FIELD(dest); > +} > + > bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *so= urce, > int short_hand, unsigned int dest, int dest_mode) > { > struct kvm_lapic *target =3D vcpu->arch.apic; > + u32 mda =3D kvm_apic_mda(dest, source, apic_x2apic_mode(target)); > =20 > apic_debug("target %p, source %p, dest 0x%x, " > "dest_mode 0x%x, short_hand 0x%x\n", > @@ -633,9 +659,9 @@ bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, s= truct kvm_lapic *source, > switch (short_hand) { > case APIC_DEST_NOSHORT: > if (dest_mode =3D=3D APIC_DEST_PHYSICAL) > - return kvm_apic_match_physical_addr(target, dest); > + return kvm_apic_match_physical_addr(target, mda); > else > - return kvm_apic_match_logical_addr(target, dest); > + return kvm_apic_match_logical_addr(target, mda); > case APIC_DEST_SELF: > return target =3D=3D source; > case APIC_DEST_ALLINC: >=20