Re: [Qemu-arm] [PATCH v3 11/15] target/arm/kvm64: Add kvm_arch_get/put_sve

[Richard Henderson]

On 8/2/19 5:25 AM, Andrew Jones wrote:
> +/*
> + * SVE registers are encoded in KVM's memory in an endianness-invariant 
> format.
> + * The byte at offset i from the start of the in-memory representation 
> contains
> + * the bits [(7 + 8 * i) : (8 * i)] of the register value. As this means the
> + * lowest offsets are stored in the lowest memory addresses, then that nearly
> + * matches QEMU's representation, which is to use an array of host-endian
> + * uint64_t's, where the lower offsets are at the lower indices. To complete
> + * the translation we just need to byte swap the uint64_t's on big-endian 
> hosts.
> + */
> +#ifdef HOST_WORDS_BIGENDIAN
> +static uint64_t *sve_bswap64(uint64_t *dst, uint64_t *src, int nr)
> +{
> +    int i;
> +
> +    for (i = 0; i < nr; ++i) {
> +        dst[i] = bswap64(src[i]);
> +    }
> +
> +    return dst;
> +}
> +#endif

Maybe better as

static uint64_t *sve_bswap64(uint64_t *tmp, uint64_t *src, int nr)
{
#ifdef HOST_WORDS_BIGENDIAN
    int i;

    for (i = 0; i < nr; ++i) {
        tmp[i] = bswap64(src[i]);
    }

    return tmp;
#else
    return src;
#endif
}

and then the rest of the ifdefs can be removed.

Otherwise,
Reviewed-by: Richard Henderson <address@hidden>


r~