| Message ID | 1380210568-23175-3-git-send-email-jonathan.austin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Sep 26, 2013 at 04:49:27PM +0100, Jonathan Austin wrote: > KVM does not have a notion of multiple clusters for CPUs, just a linear > array of CPUs. When using a system with cores in more than one cluster, the > current method for calculating the virtual MPIDR will leak the (physical) > cluster information into the virtual MPIDR. One effect of this is that > Linux under KVM fails to boot multiple CPUs that aren't in the 0th cluster. > > This patch does away with exposing the real MPIDR fields in favour of simply > using the virtual CPU number (but preserving the U bit, as before). > > Signed-off-by: Jonathan Austin <jonathan.austin@arm.com> > Acked-by: Marc Zyngier <marc.zyngier@arm.com> > --- > arch/arm/kvm/coproc_a15.c | 11 ++++------- > 1 file changed, 4 insertions(+), 7 deletions(-) > > diff --git a/arch/arm/kvm/coproc_a15.c b/arch/arm/kvm/coproc_a15.c > index cf93472..bbd4b88 100644 > --- a/arch/arm/kvm/coproc_a15.c > +++ b/arch/arm/kvm/coproc_a15.c > @@ -27,14 +27,11 @@ > static void reset_mpidr(struct kvm_vcpu *vcpu, const struct coproc_reg *r) > { > /* > - * Compute guest MPIDR: > - * (Even if we present only one VCPU to the guest on an SMP > - * host we don't set the U bit in the MPIDR, or vice versa, as > - * revealing the underlying hardware properties is likely to > - * be the best choice). > + * Compute guest MPIDR. No need to mess around with different clusters > + * but we read the 'U' bit from the underlying hardware directly. > */ > - vcpu->arch.cp15[c0_MPIDR] = (read_cpuid_mpidr() & ~MPIDR_LEVEL_MASK) > - | (vcpu->vcpu_id & MPIDR_LEVEL_MASK); > + vcpu->arch.cp15[c0_MPIDR] = (read_cpuid_mpidr() & MPIDR_SMP_BITMASK) > + | vcpu->vcpu_id; > } > > #include "coproc.h" > -- > 1.7.9.5 > > Makes sense. ack. -Christoffer
diff --git a/arch/arm/kvm/coproc_a15.c b/arch/arm/kvm/coproc_a15.c index cf93472..bbd4b88 100644 --- a/arch/arm/kvm/coproc_a15.c +++ b/arch/arm/kvm/coproc_a15.c @@ -27,14 +27,11 @@ static void reset_mpidr(struct kvm_vcpu *vcpu, const struct coproc_reg *r) { /* - * Compute guest MPIDR: - * (Even if we present only one VCPU to the guest on an SMP - * host we don't set the U bit in the MPIDR, or vice versa, as - * revealing the underlying hardware properties is likely to - * be the best choice). + * Compute guest MPIDR. No need to mess around with different clusters + * but we read the 'U' bit from the underlying hardware directly. */ - vcpu->arch.cp15[c0_MPIDR] = (read_cpuid_mpidr() & ~MPIDR_LEVEL_MASK) - | (vcpu->vcpu_id & MPIDR_LEVEL_MASK); + vcpu->arch.cp15[c0_MPIDR] = (read_cpuid_mpidr() & MPIDR_SMP_BITMASK) + | vcpu->vcpu_id; } #include "coproc.h"