On Wed, May 10, 2017 at 04:42:57PM +1000, Paul Mackerras wrote:
> POWER9 running a radix guest will take some hypervisor interrupts
> without going to real mode (turning off the MMU). This means that
> early hypercall handlers may now be called in virtual mode. Most of
> the handlers work just fine in both modes, but there are some that
> can crash the host if called in virtual mode, notably the TCE (IOMMU)
> hypercalls H_PUT_TCE, H_STUFF_TCE and H_PUT_TCE_INDIRECT. These
> already have both a real-mode and a virtual-mode version, so we
> arrange for the real-mode version to return H_TOO_HARD for radix
> guests, which will result in the virtual-mode version being called.
>
> The other hypercall which is sensitive to the MMU mode is H_RANDOM.
> It doesn't have a virtual-mode version, so this adds code to enable
> it to be called in either mode.
>
> An alternative solution was considered which would refuse to call any
> of the early hypercall handlers when doing a virtual-mode exit from a
> radix guest. However, the XICS-on-XIVE code depends on the XICS
> hypercalls being handled early even for virtual-mode exits, because
> the handlers need to be called before the XIVE vCPU state has been
> pulled off the hardware. Therefore that solution would have become
> quite invasive and complicated, and was rejected in favour of the
> simpler, though less elegant, solution presented here.
>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Tested-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Longer term we want a saner dispatch path for hypercalls in radix
mode, which will avoid this problem, but this is a worthwhile interim
fix.
> ---
> This version applies to my kvm-ppc-next branch. I'll post a backport
> to 4.12 as well.
>
> arch/powerpc/kvm/book3s_64_vio_hv.c | 13 +++++++++++++
> arch/powerpc/kvm/book3s_hv_builtin.c | 9 ++++++++-
> 2 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
> index eda0a8f6fae8..3adfd2f5301c 100644
> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> @@ -301,6 +301,10 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> /* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
> /* liobn, ioba, tce); */
>
> + /* For radix, we might be in virtual mode, so punt */
> + if (kvm_is_radix(vcpu->kvm))
> + return H_TOO_HARD;
> +
> stt = kvmppc_find_table(vcpu->kvm, liobn);
> if (!stt)
> return H_TOO_HARD;
> @@ -381,6 +385,10 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> bool prereg = false;
> struct kvmppc_spapr_tce_iommu_table *stit;
>
> + /* For radix, we might be in virtual mode, so punt */
> + if (kvm_is_radix(vcpu->kvm))
> + return H_TOO_HARD;
> +
> stt = kvmppc_find_table(vcpu->kvm, liobn);
> if (!stt)
> return H_TOO_HARD;
> @@ -491,6 +499,10 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
> long i, ret;
> struct kvmppc_spapr_tce_iommu_table *stit;
>
> + /* For radix, we might be in virtual mode, so punt */
> + if (kvm_is_radix(vcpu->kvm))
> + return H_TOO_HARD;
> +
> stt = kvmppc_find_table(vcpu->kvm, liobn);
> if (!stt)
> return H_TOO_HARD;
> @@ -527,6 +539,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
> return H_SUCCESS;
> }
>
> +/* This can be called in either virtual mode or real mode */
> long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> unsigned long ioba)
> {
> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
> index 846b40cb3a62..aea540c53607 100644
> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
> @@ -206,7 +206,14 @@ EXPORT_SYMBOL_GPL(kvmppc_hwrng_present);
>
> long kvmppc_h_random(struct kvm_vcpu *vcpu)
> {
> - if (powernv_get_random_real_mode(&vcpu->arch.gpr[4]))
> + int r;
> +
> + /* Only need to do the expensive mfmsr() on radix */
> + if (kvm_is_radix(vcpu->kvm) && (mfmsr() & MSR_IR))
> + r = powernv_get_random_long(&vcpu->arch.gpr[4]);
> + else
> + r = powernv_get_random_real_mode(&vcpu->arch.gpr[4]);
> + if (r)
> return H_SUCCESS;
>
> return H_HARDWARE;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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