Commit d078eed3 authored by David Gibson's avatar David Gibson Committed by Benjamin Herrenschmidt
Browse files

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: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Reviewed-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 7a8bf874

arch/powerpc/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -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;

arch/powerpc/kvm/powerpc.c

+18 −20
Original line number Diff line number Diff line
@@ -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;
@@ -870,10 +868,10 @@ 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 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;

		}

	}

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