powerpc: Cleanup KVM emulated load/store endian handling

Sometimes the KVM code on powerpc needs to emulate load or store
instructions from the guest, which can include both normal and byte
reversed forms.

We currently (AFAICT) handle this correctly, but some variable names are
very misleading.  In particular we use "is_bigendian" in several places to
actually mean "is the IO the same endian as the host", but we now support
little-endian powerpc hosts.  This also ties into the misleadingly named
ld_le*() and st_le*() functions, which in fact always byteswap, even on
an LE host.

This patch cleans this up by renaming to more accurate "host_swabbed", and
uses the generic swab*() functions instead of the powerpc specific and
misleadingly named ld_le*() and st_le*() functions.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 8ef05121d3cd90b51e1215cdf75a60368e18970c..c610961720c72aa075ee808f3f49044bb3664e5b 100644 (file)
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -585,7 +585,7 @@ struct kvm_vcpu_arch {
        pgd_t *pgdir;
 
        u8 io_gpr; /* GPR used as IO source/target */
-       u8 mmio_is_bigendian;
+       u8 mmio_host_swabbed;
        u8 mmio_sign_extend;
        u8 osi_needed;
        u8 osi_enabled;

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 27c0face86f45cdac10ac74ba309de04094a8367..41c5f8f8a20dbeff0e7cddf63fd5b685cffac144 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -720,7 +720,7 @@ static void kvmppc_complete_mmio_load(struct kvm_vcpu *vcpu,
                return;
        }
 
-       if (vcpu->arch.mmio_is_bigendian) {
+       if (!vcpu->arch.mmio_host_swabbed) {
                switch (run->mmio.len) {
                case 8: gpr = *(u64 *)run->mmio.data; break;
                case 4: gpr = *(u32 *)run->mmio.data; break;
@@ -728,10 +728,10 @@ static void kvmppc_complete_mmio_load(struct kvm_vcpu *vcpu,
                case 1: gpr = *(u8 *)run->mmio.data; break;
                }
        } else {
-               /* Convert BE data from userland back to LE. */
                switch (run->mmio.len) {
-               case 4: gpr = ld_le32((u32 *)run->mmio.data); break;
-               case 2: gpr = ld_le16((u16 *)run->mmio.data); break;
+               case 8: gpr = swab64(*(u64 *)run->mmio.data); break;
+               case 4: gpr = swab32(*(u32 *)run->mmio.data); break;
+               case 2: gpr = swab16(*(u16 *)run->mmio.data); break;
                case 1: gpr = *(u8 *)run->mmio.data; break;
                }
        }
@@ -780,14 +780,13 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
                       int is_default_endian)
 {
        int idx, ret;
-       int is_bigendian;
+       bool host_swabbed;
 
+       /* Pity C doesn't have a logical XOR operator */
        if (kvmppc_need_byteswap(vcpu)) {
-               /* Default endianness is "little endian". */
-               is_bigendian = !is_default_endian;
+               host_swabbed = is_default_endian;
        } else {
-               /* Default endianness is "big endian". */
-               is_bigendian = is_default_endian;
+               host_swabbed = !is_default_endian;
        }
 
        if (bytes > sizeof(run->mmio.data)) {
@@ -800,7 +799,7 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
        run->mmio.is_write = 0;
 
        vcpu->arch.io_gpr = rt;
-       vcpu->arch.mmio_is_bigendian = is_bigendian;
+       vcpu->arch.mmio_host_swabbed = host_swabbed;
        vcpu->mmio_needed = 1;
        vcpu->mmio_is_write = 0;
        vcpu->arch.mmio_sign_extend = 0;
@@ -840,14 +839,13 @@ int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
 {
        void *data = run->mmio.data;
        int idx, ret;
-       int is_bigendian;
+       bool host_swabbed;
 
+       /* Pity C doesn't have a logical XOR operator */
        if (kvmppc_need_byteswap(vcpu)) {
-               /* Default endianness is "little endian". */
-               is_bigendian = !is_default_endian;
+               host_swabbed = is_default_endian;
        } else {
-               /* Default endianness is "big endian". */
-               is_bigendian = is_default_endian;
+               host_swabbed = !is_default_endian;
        }
 
        if (bytes > sizeof(run->mmio.data)) {
@@ -862,7 +860,7 @@ int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
        vcpu->mmio_is_write = 1;
 
        /* Store the value at the lowest bytes in 'data'. */
-       if (is_bigendian) {
+       if (!host_swabbed) {
                switch (bytes) {
                case 8: *(u64 *)data = val; break;
                case 4: *(u32 *)data = val; break;
@@ -870,11 +868,11 @@ int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
                case 1: *(u8  *)data = val; break;
                }
        } else {
-               /* Store LE value into 'data'. */
                switch (bytes) {
-               case 4: st_le32(data, val); break;
-               case 2: st_le16(data, val); break;
-               case 1: *(u8 *)data = val; break;
+               case 8: *(u64 *)data = swab64(val); break;
+               case 4: *(u32 *)data = swab32(val); break;
+               case 2: *(u16 *)data = swab16(val); break;
+               case 1: *(u8  *)data = val; break;
                }
        }