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

Hi Bin,

On 19 January 2015 at 22:01, Bin Meng bmeng.cn@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@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