On Tue, Oct 02, 2018 at 09:31:28PM +1000, Paul Mackerras wrote:
> From: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
>
> The hcall H_ENTER_NESTED takes as the two parameters the address in
> L1 guest memory of a hv_regs struct and a pt_regs struct which the
> L1 guest would like to use to run a L2 guest and in which are returned
> the exit state of the L2 guest. For efficiency, these are in the
> endianness of the L1 guest, rather than being always big-endian as is
> usually the case for PAPR hypercalls.
Does that actually make a difference for efficiency? I thought the
presence of the byte-reversing loads and stores meant byteswapping was
basically zero-cost on POWER.
> When reading/writing these structures, this patch handles the case
> where the endianness of the L1 guest differs from that of the L0
> hypervisor, by byteswapping the structures after reading and before
> writing them back.
>
> Since all the fields of the pt_regs are of the same type, i.e.,
> unsigned long, we treat it as an array of unsigned longs. The fields
> of struct hv_guest_state are not all the same, so its fields are
> byteswapped individually.
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Looks correct, though, so
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
> arch/powerpc/kvm/book3s_hv_nested.c | 51 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 50 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
> index 7b1088a..228dc11 100644
> --- a/arch/powerpc/kvm/book3s_hv_nested.c
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -51,6 +51,48 @@ void kvmhv_save_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
> hr->ppr = vcpu->arch.ppr;
> }
>
> +static void byteswap_pt_regs(struct pt_regs *regs)
> +{
> + unsigned long *addr = (unsigned long *) regs;
> +
> + for (; addr < ((unsigned long *) (regs + 1)); addr++)
> + *addr = swab64(*addr);
> +}
> +
> +static void byteswap_hv_regs(struct hv_guest_state *hr)
> +{
> + hr->version = swab64(hr->version);
> + hr->lpid = swab32(hr->lpid);
> + hr->vcpu_token = swab32(hr->vcpu_token);
> + hr->lpcr = swab64(hr->lpcr);
> + hr->pcr = swab64(hr->pcr);
> + hr->amor = swab64(hr->amor);
> + hr->dpdes = swab64(hr->dpdes);
> + hr->hfscr = swab64(hr->hfscr);
> + hr->tb_offset = swab64(hr->tb_offset);
> + hr->dawr0 = swab64(hr->dawr0);
> + hr->dawrx0 = swab64(hr->dawrx0);
> + hr->ciabr = swab64(hr->ciabr);
> + hr->hdec_expiry = swab64(hr->hdec_expiry);
> + hr->purr = swab64(hr->purr);
> + hr->spurr = swab64(hr->spurr);
> + hr->ic = swab64(hr->ic);
> + hr->vtb = swab64(hr->vtb);
> + hr->hdar = swab64(hr->hdar);
> + hr->hdsisr = swab64(hr->hdsisr);
> + hr->heir = swab64(hr->heir);
> + hr->asdr = swab64(hr->asdr);
> + hr->srr0 = swab64(hr->srr0);
> + hr->srr1 = swab64(hr->srr1);
> + hr->sprg[0] = swab64(hr->sprg[0]);
> + hr->sprg[1] = swab64(hr->sprg[1]);
> + hr->sprg[2] = swab64(hr->sprg[2]);
> + hr->sprg[3] = swab64(hr->sprg[3]);
> + hr->pidr = swab64(hr->pidr);
> + hr->cfar = swab64(hr->cfar);
> + hr->ppr = swab64(hr->ppr);
> +}
> +
> static void save_hv_return_state(struct kvm_vcpu *vcpu, int trap,
> struct hv_guest_state *hr)
> {
> @@ -175,6 +217,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
> sizeof(struct hv_guest_state));
> if (err)
> return H_PARAMETER;
> + if (kvmppc_need_byteswap(vcpu))
> + byteswap_hv_regs(&l2_hv);
> if (l2_hv.version != HV_GUEST_STATE_VERSION)
> return H_P2;
>
> @@ -183,7 +227,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
> sizeof(struct pt_regs));
> if (err)
> return H_PARAMETER;
> -
> + if (kvmppc_need_byteswap(vcpu))
> + byteswap_pt_regs(&l2_regs);
> if (l2_hv.vcpu_token >= NR_CPUS)
> return H_PARAMETER;
>
> @@ -255,6 +300,10 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
> kvmhv_put_nested(l2);
>
> /* copy l2_hv_state and regs back to guest */
> + if (kvmppc_need_byteswap(vcpu)) {
> + byteswap_hv_regs(&l2_hv);
> + byteswap_pt_regs(&l2_regs);
> + }
> err = kvm_vcpu_write_guest(vcpu, hv_ptr, &l2_hv,
> sizeof(struct hv_guest_state));
> if (err)
--
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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