[xen master] x86/APIC: make connections between seemingly arbitrary numbers

[patchbot@xxxxxxx]

commit 5c04f6b4878ef92356f67fc3a192c6375ef28ec8
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Apr 5 11:38:04 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Apr 5 11:38:04 2022 +0200

    x86/APIC: make connections between seemingly arbitrary numbers
    
    Making adjustments to arbitrarily chosen values shouldn't require
    auditing the code for possible derived numbers - such a change should
    be doable in a single place, having an effect on all code depending on
    that choice.
    
    For one make the TDCR write actually use APIC_DIVISOR. With the
    necessary mask constant introduced, also use that in vLAPIC code. While
    introducing the constant, drop APIC_TDR_DIV_TMBASE: The bit has been
    undefined in halfway recent SDM and PM versions.
    
    And then introduce a constant tying together the scale used when
    converting nanoseconds to bus clocks.
    
    No functional change intended.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/apic.c                | 13 ++++++++-----
 xen/arch/x86/hvm/vlapic.c          |  6 +++---
 xen/arch/x86/include/asm/apicdef.h |  2 +-
 xen/include/xen/lib.h              |  4 ++++
 4 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/apic.c b/xen/arch/x86/apic.c
index 2f1403f00c..47e6e5fe41 100644
--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -1078,8 +1078,8 @@ static void __setup_APIC_LVTT(unsigned int clocks)
     lvtt_value = APIC_TIMER_MODE_ONESHOT | LOCAL_TIMER_VECTOR;
     apic_write(APIC_LVTT, lvtt_value);
 
-    tmp_value = apic_read(APIC_TDCR);
-    apic_write(APIC_TDCR, tmp_value | APIC_TDR_DIV_1);
+    tmp_value = apic_read(APIC_TDCR) & ~APIC_TDR_DIV_MASK;
+    apic_write(APIC_TDCR, tmp_value | PASTE(APIC_TDR_DIV_, APIC_DIVISOR));
 
     apic_write(APIC_TMICT, clocks / APIC_DIVISOR);
 }
@@ -1212,6 +1212,8 @@ uint32_t __init apic_tmcct_read(void)
  * APIC irq that way.
  */
 
+#define BUS_SCALE_SHIFT 18
+
 static void __init calibrate_APIC_clock(void)
 {
     unsigned long bus_freq; /* KAF: pointer-size avoids compile warns. */
@@ -1265,8 +1267,8 @@ static void __init calibrate_APIC_clock(void)
     /* set up multipliers for accurate timer code */
     bus_cycle  = 1000000000000UL / bus_freq; /* in pico seconds */
     bus_cycle += (1000000000000UL % bus_freq) * 2 > bus_freq;
-    bus_scale  = (1000*262144)/bus_cycle;
-    bus_scale += ((1000 * 262144) % bus_cycle) * 2 > bus_cycle;
+    bus_scale  = (1000 << BUS_SCALE_SHIFT) / bus_cycle;
+    bus_scale += ((1000 << BUS_SCALE_SHIFT) % bus_cycle) * 2 > bus_cycle;
 
     apic_printk(APIC_VERBOSE, "..... bus_scale = %#x\n", bus_scale);
     /* reset APIC to zero timeout value */
@@ -1353,7 +1355,8 @@ int reprogram_timer(s_time_t timeout)
     }
 
     if ( timeout && ((expire = timeout - NOW()) > 0) )
-        apic_tmict = min_t(u64, (bus_scale * expire) >> 18, UINT_MAX);
+        apic_tmict = min_t(uint64_t, (bus_scale * expire) >> BUS_SCALE_SHIFT,
+                           UINT32_MAX);
 
     apic_write(APIC_TMICT, (unsigned long)apic_tmict);
 
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 49be9c8ea4..257d3b6851 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -580,7 +580,7 @@ static uint32_t vlapic_get_tmcct(const struct vlapic 
*vlapic)
 static void vlapic_set_tdcr(struct vlapic *vlapic, unsigned int val)
 {
     /* Only bits 0, 1 and 3 are settable; others are MBZ. */
-    val &= 0xb;
+    val &= APIC_TDR_DIV_MASK;
     vlapic_set_reg(vlapic, APIC_TDCR, val);
 
     /* Update the demangled hw.timer_divisor. */
@@ -888,7 +888,7 @@ void vlapic_reg_write(struct vcpu *v, unsigned int reg, 
uint32_t val)
     {
         uint32_t current_divisor = vlapic->hw.timer_divisor;
 
-        vlapic_set_tdcr(vlapic, val & 0xb);
+        vlapic_set_tdcr(vlapic, val);
 
         vlapic_update_timer(vlapic, vlapic_get_reg(vlapic, APIC_LVTT), false,
                             current_divisor);
@@ -1020,7 +1020,7 @@ int guest_wrmsr_x2apic(struct vcpu *v, uint32_t msr, 
uint64_t msr_content)
         break;
 
     case APIC_TDCR:
-        if ( msr_content & ~APIC_TDR_DIV_1 )
+        if ( msr_content & ~APIC_TDR_DIV_MASK )
             return X86EMUL_EXCEPTION;
         break;
 
diff --git a/xen/arch/x86/include/asm/apicdef.h 
b/xen/arch/x86/include/asm/apicdef.h
index 0633da9fe1..2440d83c8d 100644
--- a/xen/arch/x86/include/asm/apicdef.h
+++ b/xen/arch/x86/include/asm/apicdef.h
@@ -106,7 +106,7 @@
 #define                APIC_TMICT      0x380
 #define                APIC_TMCCT      0x390
 #define                APIC_TDCR       0x3E0
-#define                        APIC_TDR_DIV_TMBASE     (1<<2)
+#define                        APIC_TDR_DIV_MASK       0xB
 #define                        APIC_TDR_DIV_1          0xB
 #define                        APIC_TDR_DIV_2          0x0
 #define                        APIC_TDR_DIV_4          0x1
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index bf6470a2e7..b9b24a0436 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -13,6 +13,10 @@
 #define count_args(args...) \
     count_args_(., ## args, 8, 7, 6, 5, 4, 3, 2, 1, 0)
 
+/* Indirect macros required for expanded argument pasting. */
+#define PASTE_(a, b) a ## b
+#define PASTE(a, b) PASTE_(a, b)
+
 #ifndef __ASSEMBLY__
 
 #include <xen/inttypes.h>
--
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