Re: [PATCH v3 29/33] KVM: PPC: Book3S HV: Handle differing endianness for H_ENTER_NESTED
From: David Gibson <hidden>
Date: 2018-10-03 06:36:36
Also in:
kvm
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 <redacted>
Looks correct, though, so Reviewed-by: David Gibson <redacted>
quoted hunk ↗ jump to hunk
--- 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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