[Xen-changelog] No C1-Clock Ramp disabling on AMD processors. The tiny drift

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 9eb1a1a6e16d2bf766839b55aaa5e8e47337d539
# Parent  d3547993be94d8f9c2f98513630d5903062829e3
No C1-Clock Ramp disabling on AMD processors. The tiny drift
caused by the ramping changes should not cause TSCs to become
noticeably out of sync on Xen systems.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r d3547993be94 -r 9eb1a1a6e16d xen/arch/x86/cpu/amd.c
--- a/xen/arch/x86/cpu/amd.c    Mon Feb  6 15:41:26 2006
+++ b/xen/arch/x86/cpu/amd.c    Mon Feb  6 15:51:06 2006
@@ -3,19 +3,12 @@
 #include <xen/bitops.h>
 #include <xen/mm.h>
 #include <xen/smp.h>
-#include <xen/sched.h>
 #include <asm/io.h>
 #include <asm/msr.h>
 #include <asm/processor.h>
-#include <asm/hvm/vcpu.h>
 #include <asm/hvm/support.h>
 
-
 #include "cpu.h"
-
-
-#define                AMD_C1_CLOCK_RAMP                       0x80000084
-#define                AMD_ADVPM_TSC_INVARIANT         0x80000007
 
 /*
  * amd_flush_filter={on,off}. Forcibly Enable or disable the TLB flush
@@ -48,99 +41,6 @@
  
 extern void vide(void);
 __asm__(".text\n.align 4\nvide: ret");
-
-
-/*
- *     Check if C1-Clock ramping enabled in  PMM7.CpuLowPwrEnh
- *     On 8th-Generation cores only. Assume BIOS has setup
- *     all Northbridges equivalently.
- */
-
-static int c1_ramp_8gen(void) 
-{
-       u32 l;
-
-       /*      Read dev=0x18, function = 3, offset=0x87  */
-       l = AMD_C1_CLOCK_RAMP;
-       /*      fill in dev (18) + function (3) */
-       /*      direct cfc/cf8 should be safe here */
-       l += (((0x18) << 3) + 0x3) << 8; 
-       outl(l, 0xcf8);
-       return (1 & (inl(0xcfc) >> 24));
-}
-
-/*
- * returns TRUE if ok to use TSC
- */
-
-static int use_amd_tsc(struct cpuinfo_x86 *c) 
-{ 
-       if (c->x86 < 0xf) {
-               /*
-                *      TSC drift doesn't exist on 7th Gen or less
-                *      However, OS still needs to consider effects
-                *      of P-state changes on TSC
-               */
-               return 1;
-       } else if ( cpuid_edx(AMD_ADVPM_TSC_INVARIANT) & 0x100 ) {
-               /*
-                *      CPUID.AdvPowerMgmtInfo.TscInvariant
-                *      EDX bit 8, 8000_0007
-                *      Invariant TSC on 8th Gen or newer, use it
-                *      (assume all cores have invariant TSC)
-               */
-               return 1;
-       } else if ((mp_get_num_processors() == 1) && (c->x86_num_cores == 1)) {
-               /*
-                *      OK to use TSC on uni-processor-uni-core
-                *      However, OS still needs to consider effects
-                *      of P-state changes on TSC
-               */
-               return 1;
-       } else if ( (mp_get_num_processors() == 1) && (c->x86 == 0x0f) 
-                               && !c1_ramp_8gen()) {
-               /*
-                *      Use TSC on 8th Gen uni-proc with C1_ramp off 
-                *      However, OS still needs to consider effects
-                *      of P-state changes on TSC
-               */
-               return 1;
-       } else { 
-               return 0;
-       }
-}
-
-/*
- *     Disable C1-Clock ramping if enabled in PMM7.CpuLowPwrEnh
- *     On 8th-Generation cores only. Assume BIOS has setup
- *     all Northbridges equivalently.
- */
-
-static void amd_disable_c1_ramping(void) 
-{
-       u32 l, h;
-       int i;
-
-       for (i=0; i < NR_CPUS;i++) {
-               /* Read from the Northbridge for Node x. until we get invalid 
data */
-               /* fill in dev (18 + cpu#) + function (3) */
-               l = AMD_C1_CLOCK_RAMP + ((((0x18 + i) << 3) + 0x3) << 8);
-               /*      direct cfc/cf8 should be safe here */
-               outl(l, 0xcf8);
-               h = inl(0xcfc);
-               if (h != 0xFFFFFFFF) {
-                       h &= 0xFCFFFFFF; /* clears pmm7[1:0]  */
-                       outl(l, 0xcf8);
-                       outl(h, 0xcfc);
-                       printk ("AMD: Disabling C1 Clock Ramping Node #%x\n",i);
-               }
-               else {
-                       i = NR_CPUS;
-               }
-                       
-       }
-       return;
-}
 
 static void __init init_amd(struct cpuinfo_x86 *c)
 {
@@ -347,14 +247,6 @@
                       cpu, c->x86_num_cores, cpu_core_id[cpu]);
        }
 #endif
-       /*
-        * Prevent TSC drift in non single-processor, single-core platforms
-        */
-       if ( !use_amd_tsc(c) && (c->x86 == 0x0f) && c1_ramp_8gen() && 
-                       (smp_processor_id() == 0)) {
-               /* Disable c1 Clock Ramping on all cores */
-               amd_disable_c1_ramping();
-       }
 
 #ifdef CONFIG_SVM
        start_svm();
diff -r d3547993be94 -r 9eb1a1a6e16d xen/arch/x86/mpparse.c
--- a/xen/arch/x86/mpparse.c    Mon Feb  6 15:41:26 2006
+++ b/xen/arch/x86/mpparse.c    Mon Feb  6 15:51:06 2006
@@ -730,11 +730,6 @@
         */
 }
 
-int __init mp_get_num_processors(void)
-{
-    return num_processors;
-}
-
 static int __init smp_scan_config (unsigned long base, unsigned long length)
 {
        unsigned int *bp = maddr_to_virt(base);
diff -r d3547993be94 -r 9eb1a1a6e16d xen/include/asm-x86/mpspec.h
--- a/xen/include/asm-x86/mpspec.h      Mon Feb  6 15:41:26 2006
+++ b/xen/include/asm-x86/mpspec.h      Mon Feb  6 15:51:06 2006
@@ -35,7 +35,6 @@
 extern void mp_override_legacy_irq (u8 bus_irq, u8 polarity, u8 trigger, u32 
gsi);
 extern void mp_config_acpi_legacy_irqs (void);
 extern int mp_register_gsi (u32 gsi, int edge_level, int active_high_low);
-extern int mp_get_num_processors(void);
 #endif /*CONFIG_ACPI_BOOT*/
 
 #define PHYSID_ARRAY_SIZE      BITS_TO_LONGS(MAX_APICS)

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