On 04/10/2016 11:07, Thomas Huth wrote:
> Transactional memory is currently only supported on KVM-HV, and
> not yet on KVM-PR. So it's better to check the device tree first
> and fail gracefully if it is not available.
>
> Reviewed-by: Laurent Vivier <lvivier@xxxxxxxxxx>
> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
> ---
> v3:
> - Removed unnecessary check for "plen >= 26" in cpu_has_tm()
>
> v2:
> - Reworked the check for the "ibm,pa-features" and added a comment
> - Use a dedicated variable "has_tm" instead of "i" in main()
>
> powerpc/tm.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 42 insertions(+), 1 deletion(-)
>
> diff --git a/powerpc/tm.c b/powerpc/tm.c
> index 6ce750a..b611061 100644
> --- a/powerpc/tm.c
> +++ b/powerpc/tm.c
> @@ -10,6 +10,41 @@
> #include <asm/processor.h>
> #include <asm/handlers.h>
> #include <asm/smp.h>
> +#include <asm/setup.h>
> +#include <devicetree.h>
> +
> +/* Check "ibm,pa-features" property of a CPU node for the TM flag */
> +static void cpu_has_tm(int fdtnode, u32 regval __unused, void *ptr)
> +{
> + const struct fdt_property *prop;
> + int plen;
> +
> + prop = fdt_get_property(dt_fdt(), fdtnode, "ibm,pa-features", &plen);
> + if (!prop) /* No features means TM is also not available */
> + return;
> + /* Sanity check for the property layout (first two bytes are header) */
> + assert(plen >= 8 && prop->data[1] == 0 && prop->data[0] <= plen - 2);
> +
> + /*
> + * The "Transactional Memory Category Support" flags are at byte
> + * offset 22 and 23 of the attribute type 0, so when adding the
> + * two bytes for the header, we've got to look at offset 24 for
> + * the TM support bit.
> + */
> + if (prop->data[0] >= 24 && (prop->data[24] & 0x80) != 0)
> + *(int *)ptr += 1;
> +}
in the future, if we think we can have more than the type 0, we should
scan the property with something like:
off = 0
while (off + 1 < plen) {
if (prop->data[off + 1] != 0) {
off += 2 + prop->data[off];
continue;
}
... check TM ...
}
but I don't think we need that now...
Laurent
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