CCing a larger audience. Please review. On 10/23/2018 03:51 PM, Jaggi, Manish wrote: > From: Manish Jaggi <manish.jaggi@xxxxxxxxxx> > > This patch introduces an error code KVM_EINVARIANT which is returned > by KVM when userland tries to set an invariant register. > > The need for this error code is in VM Migration for arm64. > ARM64 systems use mainly -machine virt -cpu host as parameter to qemu. > Migration requires both Source and destination machines to have same > physical cpu. There are cases where the overall architecture of CPU is > same but the next version of the chip with some bug fixes which have no > effect on qemu operation. In such cases invariant registers like MIDR > have a different value. > Currently Migration fails in such cases. > > Rather than sending a EINVAL, a specifc error code will help > userland program the guest invariant register by querying the migrated > host machines invariant registers. > > Qemu will have a parameter -hostinvariant along with checking of this > error code. So it can be safely assumed that the feature is opt-in > > Corresponding Qemu patchset can be found at : > https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg05048.html > > > Signed-off-by: Manish Jaggi <manish.jaggi@xxxxxxxxxx> > --- > arch/arm64/kvm/sys_regs.c | 9 ++++----- > include/uapi/linux/kvm_para.h | 1 + > 2 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 22fbbdb..78ffc02 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1111,7 +1111,7 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr, > > /* This is what we mean by invariant: you can't change it. */ > if (val != read_id_reg(rd, raz)) > - return -EINVAL; > + return -KVM_EINVARIANT; > > return 0; > } > @@ -2254,9 +2254,8 @@ static int set_invariant_sys_reg(u64 id, void __user *uaddr) > return err; > > /* This is what we mean by invariant: you can't change it. */ > - if (r->val != val) > - return -EINVAL; > - > + if (r->val != val) > + return -KVM_EINVARIANT; > return 0; > } > > @@ -2335,7 +2334,7 @@ static int demux_c15_set(u64 id, void __user *uaddr) > > /* This is also invariant: you can't change it. */ > if (newval != get_ccsidr(val)) > - return -EINVAL; > + return -KVM_EINVARIANT; > return 0; > default: > return -ENOENT; > diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h > index 6c0ce49..4358669 100644 > --- a/include/uapi/linux/kvm_para.h > +++ b/include/uapi/linux/kvm_para.h > @@ -17,6 +17,7 @@ > #define KVM_E2BIG E2BIG > #define KVM_EPERM EPERM > #define KVM_EOPNOTSUPP 95 > +#define KVM_EINVARIANT 96 > > #define KVM_HC_VAPIC_POLL_IRQ 1 > #define KVM_HC_MMU_OP 2 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
