[U-Boot] [PATCH 3/3] x86: Test mtrr support flag before accessing mtrr msr

[Simon Glass]

Hi Bin,

On 19 January 2015 at 22:01, Bin Meng <bmeng.cn at gmail.com> wrote:
> On some x86 processors (like Intel Quark) the MTRR registers are not
> supported. This is reflected by the CPUID (EAX 01H) result EDX[12].
> Accessing the MTRR registers on such processors will cause #GP so we
> must test the support flag before accessing MTRR MSRs.
>
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
> ---
>
>  arch/x86/cpu/mtrr.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/arch/x86/cpu/mtrr.c b/arch/x86/cpu/mtrr.c
> index ac8765f..68f1b04 100644
> --- a/arch/x86/cpu/mtrr.c
> +++ b/arch/x86/cpu/mtrr.c
> @@ -22,6 +22,9 @@ DECLARE_GLOBAL_DATA_PTR;
>  /* Prepare to adjust MTRRs */
>  void mtrr_open(struct mtrr_state *state)
>  {
> +       if (!gd->arch.has_mtrr)
> +               return;
> +
>         state->enable_cache = dcache_status();
>
>         if (state->enable_cache)
> @@ -33,6 +36,9 @@ void mtrr_open(struct mtrr_state *state)
>  /* Clean up after adjusting MTRRs, and enable them */
>  void mtrr_close(struct mtrr_state *state)
>  {
> +       if (!gd->arch.has_mtrr)
> +               return;
> +
>         wrmsrl(MTRR_DEF_TYPE_MSR, state->deftype | MTRR_DEF_TYPE_EN);
>         if (state->enable_cache)
>                 enable_caches();
> @@ -45,6 +51,9 @@ int mtrr_commit(bool do_caches)
>         uint64_t mask;
>         int i;
>
> +       if (!gd->arch.has_mtrr)
> +               return 0;
> +
>         mtrr_open(&state);
>         for (i = 0; i < gd->arch.mtrr_req_count; i++, req++) {
>                 mask = ~(req->size - 1);
> @@ -66,6 +75,9 @@ int mtrr_add_request(int type, uint64_t start, uint64_t size)
>         struct mtrr_request *req;
>         uint64_t mask;
>
> +       if (!gd->arch.has_mtrr)
> +               return 0;

Shouldn't this (and the above) return -ENOSYS?

> +
>         if (gd->arch.mtrr_req_count == MAX_MTRR_REQUESTS)
>                 return -ENOSPC;
>         req = &gd->arch.mtrr_req[gd->arch.mtrr_req_count++];
> --
> 1.8.2.1
>

Regards,
Simon