| Message ID | 1538479892-14835-30-git-send-email-paulus@ozlabs.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: PPC: Book3S HV: Nested HV virtualization | expand |
On Tue, Oct 02, 2018 at 09:31:28PM +1000, Paul Mackerras wrote: > From: Suraj Jitindar Singh <sjitindarsingh@gmail.com> > > 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@gmail.com> > Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Looks correct, though, so Reviewed-by: David Gibson <david@gibson.dropbear.id.au> > --- > 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)
On Wed, Oct 03, 2018 at 04:13:36PM +1000, David Gibson wrote: > On Tue, Oct 02, 2018 at 09:31:28PM +1000, Paul Mackerras wrote: > > From: Suraj Jitindar Singh <sjitindarsingh@gmail.com> > > > > 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. It means that the L1 hypervisor can pass a pointer to the regs struct in the kvm_vcpu struct rather than having to make a copy, and copy the values back after the H_ENTER_NESTED. I'll reword the commit message to say it's mostly about convenience and to a lesser extent about performance. Paul.
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)