Re: [Qemu-devel] [PULL 16/19] kvm: fix ioeventfd endianness on bi-endian architectures

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Wed, 18 Mar 2015 12:25:03 +0100
Paolo Bonzini <pbonzini@redhat.com> wrote:
> From: Greg Kurz <gkurz@linux.vnet.ibm.com>
> 
> KVM expects host endian values. Hosts that don't use the default endianness
> need to negate the swap performed in adjust_endianness().
> 
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Message-Id: <20150313212337.31142.3991.stgit@bahia.local>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---

I forgot to Cc qemu-stable@ but I think we really should have this one
in 2.2 to support ppc64le hosts.

--
G

>  kvm-all.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index 55025cc..335438a 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -528,13 +528,33 @@ int kvm_vm_check_extension(KVMState *s, unsigned int extension)
>      return ret;
>  }
> 
> +static uint32_t adjust_ioeventfd_endianness(uint32_t val, uint32_t size)
> +{
> +#if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
> +    /* The kernel expects ioeventfd values in HOST_WORDS_BIGENDIAN
> +     * endianness, but the memory core hands them in target endianness.
> +     * For example, PPC is always treated as big-endian even if running
> +     * on KVM and on PPC64LE.  Correct here.
> +     */
> +    switch (size) {
> +    case 2:
> +        val = bswap16(val);
> +        break;
> +    case 4:
> +        val = bswap32(val);
> +        break;
> +    }
> +#endif
> +    return val;
> +}
> +
>  static int kvm_set_ioeventfd_mmio(int fd, hwaddr addr, uint32_t val,
>                                    bool assign, uint32_t size, bool datamatch)
>  {
>      int ret;
>      struct kvm_ioeventfd iofd;
> 
> -    iofd.datamatch = datamatch ? val : 0;
> +    iofd.datamatch = datamatch ? adjust_ioeventfd_endianness(val, size) : 0;
>      iofd.addr = addr;
>      iofd.len = size;
>      iofd.flags = 0;
> @@ -564,7 +584,7 @@ static int kvm_set_ioeventfd_pio(int fd, uint16_t addr, uint16_t val,
>                                   bool assign, uint32_t size, bool datamatch)
>  {
>      struct kvm_ioeventfd kick = {
> -        .datamatch = datamatch ? val : 0,
> +        .datamatch = datamatch ? adjust_ioeventfd_endianness(val, size) : 0,
>          .addr = addr,
>          .flags = KVM_IOEVENTFD_FLAG_PIO,
>          .len = size,