[PATCH] x86/MTRR: avoid several indirect calls

[Jan Beulich <jbeulich@xxxxxxxx>]

The use of (supposedly) vendor-specific hooks is a relic from the days
when Xen was still possible to build as 32-bit binary. There's no
expectation that a new need for such an abstraction would arise. Convert
mttr_if to a mere boolean and all prior calls through it to direct ones,
thus allowing to eliminate 6 ENDBR from .text.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Strictly speaking mtrr_if could go apparently away as well, for
effectively mirroring cpu_has_mtrr now (once mtrr_bp_init() has run).
Replacing the variable uses would be further code churn, though.

--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -287,7 +287,7 @@ static void set_fixed_range(int msr, boo
        }
 }
 
-int cf_check generic_get_free_region(
+int mtrr_get_free_region(
     unsigned long base, unsigned long size, int replace_reg)
 /*  [SUMMARY] Get a free MTRR.
     <base> The starting (base) address of the region.
@@ -303,14 +303,14 @@ int cf_check generic_get_free_region(
        if (replace_reg >= 0 && replace_reg < max)
                return replace_reg;
        for (i = 0; i < max; ++i) {
-               mtrr_if->get(i, &lbase, &lsize, &ltype);
+               mtrr_get(i, &lbase, &lsize, &ltype);
                if (lsize == 0)
                        return i;
        }
        return -ENOSPC;
 }
 
-static void cf_check generic_get_mtrr(
+void mtrr_get(
     unsigned int reg, unsigned long *base, unsigned long *size, mtrr_type 
*type)
 {
        uint64_t _mask, _base;
@@ -500,7 +500,7 @@ static void post_set(bool pge)
        spin_unlock(&set_atomicity_lock);
 }
 
-static void cf_check generic_set_all(void)
+void mtrr_set_all(void)
 {
        unsigned long mask, count;
        unsigned long flags;
@@ -523,7 +523,7 @@ static void cf_check generic_set_all(voi
        }
 }
 
-static void cf_check generic_set_mtrr(
+void mtrr_set(
     unsigned int reg, unsigned long base, unsigned long size, mtrr_type type)
 /*  [SUMMARY] Set variable MTRR register on the local CPU.
     <reg> The register to set.
@@ -567,7 +567,7 @@ static void cf_check generic_set_mtrr(
        local_irq_restore(flags);
 }
 
-int cf_check generic_validate_add_page(
+int mtrr_validate_add_page(
     unsigned long base, unsigned long size, unsigned int type)
 {
        unsigned long lbase, last;
@@ -586,21 +586,9 @@ int cf_check generic_validate_add_page(
 }
 
 
-static int cf_check generic_have_wrcomb(void)
+bool mtrr_have_wrcomb(void)
 {
        unsigned long config;
        rdmsrl(MSR_MTRRcap, config);
        return (config & (1ULL << 10));
 }
-
-/* generic structure...
- */
-const struct mtrr_ops generic_mtrr_ops = {
-       .use_intel_if      = true,
-       .set_all           = generic_set_all,
-       .get               = generic_get_mtrr,
-       .get_free_region   = generic_get_free_region,
-       .set               = generic_set_mtrr,
-       .validate_add_page = generic_validate_add_page,
-       .have_wrcomb       = generic_have_wrcomb,
-};
--- a/xen/arch/x86/cpu/mtrr/main.c
+++ b/xen/arch/x86/cpu/mtrr/main.c
@@ -57,7 +57,7 @@ static DEFINE_MUTEX(mtrr_mutex);
 u64 __read_mostly size_or_mask;
 u64 __read_mostly size_and_mask;
 
-const struct mtrr_ops *__read_mostly mtrr_if = NULL;
+static bool __ro_after_init mtrr_if;
 
 static void set_mtrr(unsigned int reg, unsigned long base,
                     unsigned long size, mtrr_type type);
@@ -78,23 +78,12 @@ static const char *mtrr_attrib_to_str(in
        return (x <= 6) ? mtrr_strings[x] : "?";
 }
 
-/*  Returns non-zero if we have the write-combining memory type  */
-static int have_wrcomb(void)
-{
-       return (mtrr_if->have_wrcomb ? mtrr_if->have_wrcomb() : 0);
-}
-
 /*  This function returns the number of variable MTRRs  */
 static void __init set_num_var_ranges(void)
 {
-       unsigned long config = 0;
+       unsigned long config;
 
-       if (use_intel()) {
-               rdmsrl(MSR_MTRRcap, config);
-       } else if (is_cpu(AMD))
-               config = 2;
-       else if (is_cpu(CENTAUR))
-               config = 8;
+       rdmsrl(MSR_MTRRcap, config);
        num_var_ranges = MASK_EXTR(config, MTRRcap_VCNT);
 }
 
@@ -149,10 +138,10 @@ static void cf_check ipi_handler(void *i
        if (data->smp_reg == ~0U) /* update all mtrr registers */
                /* At the cpu hot-add time this will reinitialize mtrr 
                 * registres on the existing cpus. It is ok.  */
-               mtrr_if->set_all();
+               mtrr_set_all();
        else /* single mtrr register update */
-               mtrr_if->set(data->smp_reg, data->smp_base, 
-                            data->smp_size, data->smp_type);
+               mtrr_set(data->smp_reg, data->smp_base,
+                        data->smp_size, data->smp_type);
 
        atomic_dec(&data->count);
        while(atomic_read(&data->gate))
@@ -198,10 +187,9 @@ static inline int types_compatible(mtrr_
  * of CPUs. As each CPU disables interrupts, it'll decrement it once. We wait
  * until it hits 0 and proceed. We set the data.gate flag and reset data.count.
  * Meanwhile, they are waiting for that flag to be set. Once it's set, each 
- * CPU goes through the transition of updating MTRRs. The CPU vendors may each 
do it 
- * differently, so we call mtrr_if->set() callback and let them take care of 
it.
- * When they're done, they again decrement data->count and wait for data.gate 
to 
- * be reset. 
+ * CPU goes through the transition of updating MTRRs.
+ * When mtrr_set() is done, they again decrement data->count and wait for
+ * data.gate to be reset.
  * When we finish, we wait for data.count to hit 0 and toggle the data.gate 
flag.
  * Everyone then enables interrupts and we all continue on.
  *
@@ -251,9 +239,9 @@ static void set_mtrr(unsigned int reg, u
        if (reg == ~0U)  /* update all mtrr registers */
                /* at boot or resume time, this will reinitialize the mtrrs on 
                 * the bp. It is ok. */
-               mtrr_if->set_all();
+               mtrr_set_all();
        else /* update the single mtrr register */
-               mtrr_if->set(reg,base,size,type);
+               mtrr_set(reg, base, size, type);
 
        /* wait for the others */
        while (atomic_read(&data.count))
@@ -319,7 +307,7 @@ int mtrr_add_page(unsigned long base, un
        if (!mtrr_if)
                return -ENXIO;
                
-       if ((error = mtrr_if->validate_add_page(base,size,type)))
+       if ((error = mtrr_validate_add_page(base, size, type)))
                return error;
 
        if (type >= MTRR_NUM_TYPES) {
@@ -328,7 +316,7 @@ int mtrr_add_page(unsigned long base, un
        }
 
        /*  If the type is WC, check that this processor supports it  */
-       if ((type == X86_MT_WC) && !have_wrcomb()) {
+       if ((type == X86_MT_WC) && mtrr_have_wrcomb()) {
                printk(KERN_WARNING
                       "mtrr: your processor doesn't support 
write-combining\n");
                return -EOPNOTSUPP;
@@ -350,7 +338,7 @@ int mtrr_add_page(unsigned long base, un
        /*  Search for existing MTRR  */
        mutex_lock(&mtrr_mutex);
        for (i = 0; i < num_var_ranges; ++i) {
-               mtrr_if->get(i, &lbase, &lsize, &ltype);
+               mtrr_get(i, &lbase, &lsize, &ltype);
                if (!lsize || base > lbase + lsize - 1 || base + size - 1 < 
lbase)
                        continue;
                /*  At this point we know there is some kind of 
overlap/enclosure  */
@@ -385,7 +373,7 @@ int mtrr_add_page(unsigned long base, un
                goto out;
        }
        /*  Search for an empty MTRR  */
-       i = mtrr_if->get_free_region(base, size, replace);
+       i = mtrr_get_free_region(base, size, replace);
        if (i >= 0) {
                set_mtrr(i, base, size, type);
                if (likely(replace < 0))
@@ -494,7 +482,7 @@ int mtrr_del_page(int reg, unsigned long
        if (reg < 0) {
                /*  Search for existing MTRR  */
                for (i = 0; i < max; ++i) {
-                       mtrr_if->get(i, &lbase, &lsize, &ltype);
+                       mtrr_get(i, &lbase, &lsize, &ltype);
                        if (lbase == base && lsize == size) {
                                reg = i;
                                break;
@@ -510,7 +498,7 @@ int mtrr_del_page(int reg, unsigned long
                printk(KERN_WARNING "mtrr: register: %d too big\n", reg);
                goto out;
        }
-       mtrr_if->get(reg, &lbase, &lsize, &ltype);
+       mtrr_get(reg, &lbase, &lsize, &ltype);
        if (lsize < 1) {
                printk(KERN_WARNING "mtrr: MTRR %d not used\n", reg);
                goto out;
@@ -568,7 +556,7 @@ struct mtrr_value {
 void __init mtrr_bp_init(void)
 {
        if (cpu_has_mtrr) {
-               mtrr_if = &generic_mtrr_ops;
+               mtrr_if = true;
                size_or_mask = ~((1ULL << (paddr_bits - PAGE_SHIFT)) - 1);
                size_and_mask = ~size_or_mask & 0xfffff00000ULL;
        }
@@ -576,14 +564,13 @@ void __init mtrr_bp_init(void)
        if (mtrr_if) {
                set_num_var_ranges();
                init_table();
-               if (use_intel())
-                       get_mtrr_state();
+               get_mtrr_state();
        }
 }
 
 void mtrr_ap_init(void)
 {
-       if (!mtrr_if || !use_intel() || hold_mtrr_updates_on_aps)
+       if (!mtrr_if || hold_mtrr_updates_on_aps)
                return;
        /*
         * Ideally we should hold mtrr_mutex here to avoid mtrr entries changed,
@@ -612,32 +599,25 @@ void mtrr_save_state(void)
 
 void mtrr_aps_sync_begin(void)
 {
-       if (!use_intel())
-               return;
        hold_mtrr_updates_on_aps = 1;
 }
 
 void mtrr_aps_sync_end(void)
 {
-       if (!use_intel())
-               return;
        set_mtrr(~0U, 0, 0, 0);
        hold_mtrr_updates_on_aps = 0;
 }
 
 void mtrr_bp_restore(void)
 {
-       if (!use_intel())
-               return;
-       mtrr_if->set_all();
+       mtrr_set_all();
 }
 
 static int __init cf_check mtrr_init_finialize(void)
 {
        if (!mtrr_if)
                return 0;
-       if (use_intel())
-               mtrr_state_warn();
+       mtrr_state_warn();
        return 0;
 }
 __initcall(mtrr_init_finialize);
--- a/xen/arch/x86/cpu/mtrr/mtrr.h
+++ b/xen/arch/x86/cpu/mtrr/mtrr.h
@@ -6,40 +6,21 @@
 #define MTRR_CHANGE_MASK_VARIABLE  0x02
 #define MTRR_CHANGE_MASK_DEFTYPE   0x04
 
-
-struct mtrr_ops {
-       u32     vendor;
-       bool    use_intel_if;
-//     void    (*init)(void);
-       void    (*set)(unsigned int reg, unsigned long base,
-                      unsigned long size, mtrr_type type);
-       void    (*set_all)(void);
-
-       void    (*get)(unsigned int reg, unsigned long *base,
-                      unsigned long *size, mtrr_type * type);
-       int     (*get_free_region)(unsigned long base, unsigned long size,
-                                  int replace_reg);
-       int     (*validate_add_page)(unsigned long base, unsigned long size,
-                                    unsigned int type);
-       int     (*have_wrcomb)(void);
-};
-
-int cf_check generic_get_free_region(
+void mtrr_get(
+    unsigned int reg, unsigned long *base, unsigned long *size,
+    mtrr_type *type);
+void mtrr_set(
+    unsigned int reg, unsigned long base, unsigned long size, mtrr_type type);
+void mtrr_set_all(void);
+int mtrr_get_free_region(
     unsigned long base, unsigned long size, int replace_reg);
-int cf_check generic_validate_add_page(
+int mtrr_validate_add_page(
     unsigned long base, unsigned long size, unsigned int type);
-
-extern const struct mtrr_ops generic_mtrr_ops;
+bool mtrr_have_wrcomb(void);
 
 void get_mtrr_state(void);
 
-extern void set_mtrr_ops(const struct mtrr_ops *);
-
 extern u64 size_or_mask, size_and_mask;
-extern const struct mtrr_ops *mtrr_if;
-
-#define is_cpu(vnd)    (mtrr_if && mtrr_if->vendor == X86_VENDOR_##vnd)
-#define use_intel()    (mtrr_if && mtrr_if->use_intel_if)
 
 extern unsigned int num_var_ranges;
 
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -295,7 +295,7 @@ ret_t do_platform_op(
         ret = -EINVAL;
         if ( op->u.read_memtype.reg < num_var_ranges )
         {
-            mtrr_if->get(op->u.read_memtype.reg, &mfn, &nr_mfns, &type);
+            mtrr_get(op->u.read_memtype.reg, &mfn, &nr_mfns, &type);
             op->u.read_memtype.mfn     = mfn;
             op->u.read_memtype.nr_mfns = nr_mfns;
             op->u.read_memtype.type    = type;