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Subject[PATCH v4.16-rc5 2/3] x86/vdso: on Intel, VDSO should handle CLOCK_MONOTONIC_RAW
Date
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index fbc7371..2c46675 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -184,10 +184,9 @@ notrace static u64 vread_tsc(void)

notrace static u64 vread_tsc_raw(void)
{
- u64 tsc
+ u64 tsc = (gtod->has_rdtscp ? rdtscp((void*)0) : rdtsc_ordered())
, last = gtod->raw_cycle_last;

- tsc = rdtsc_ordered();
if (likely(tsc >= last))
return tsc;
asm volatile ("");
diff --git a/arch/x86/entry/vsyscall/vsyscall_gtod.c b/arch/x86/entry/vsyscall/vsyscall_gtod.c
index 5af7093..0327a95 100644
--- a/arch/x86/entry/vsyscall/vsyscall_gtod.c
+++ b/arch/x86/entry/vsyscall/vsyscall_gtod.c
@@ -16,6 +16,9 @@
#include <linux/timekeeper_internal.h>
#include <asm/vgtod.h>
#include <asm/vvar.h>
+#include <asm/cpufeature.h>
+
+extern unsigned tsc_khz;

int vclocks_used __read_mostly;

@@ -49,6 +52,7 @@ void update_vsyscall(struct timekeeper *tk)
vdata->raw_mask = tk->tkr_raw.mask;
vdata->raw_mult = tk->tkr_raw.mult;
vdata->raw_shift = tk->tkr_raw.shift;
+ vdata->has_rdtscp = static_cpu_has(X86_FEATURE_RDTSCP);

vdata->wall_time_sec = tk->xtime_sec;
vdata->wall_time_snsec = tk->tkr_mono.xtime_nsec;
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 30df295..a5ff704 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -218,6 +218,36 @@ static __always_inline unsigned long long rdtsc_ordered(void)
return rdtsc();
}

+/**
+ * rdtscp() - read the current TSC and (optionally) CPU number, with built-in
+ * cancellation point replacing barrier - only available
+ * if static_cpu_has(X86_FEATURE_RDTSCP) .
+ * returns: The 64-bit Time Stamp Counter (TSC) value.
+ * Optionally, 'cpu_out' can be non-null, and on return it will contain
+ * the number (Intel CPU ID) of the CPU that the task is currently running on.
+ * As does EAX_EDT_RET, this uses the "open-coded asm" style to
+ * force the compiler + assembler to always use (eax, edx, ecx) registers,
+ * NOT whole (rax, rdx, rcx) on x86_64 , because only 32-bit
+ * variables are used - exactly the same code should be generated
+ * for this instruction on 32-bit as on 64-bit when this asm stanza is used.
+ * See: SDM , Vol #2, RDTSCP instruction.
+ */
+static __always_inline u64 rdtscp(u32 *cpu_out)
+{
+ u32 tsc_lo, tsc_hi, tsc_cpu;
+ asm volatile
+ ( "rdtscp"
+ : "=a" (tsc_lo)
+ , "=d" (tsc_hi)
+ , "=c" (tsc_cpu)
+ ); // : eax, edx, ecx used - NOT rax, rdx, rcx
+ if (unlikely(cpu_out != ((void*)0)))
+ *cpu_out = tsc_cpu;
+ return ((((u64)tsc_hi) << 32) |
+ (((u64)tsc_lo) & 0x0ffffffffULL )
+ );
+}
+
/* Deprecated, keep it for a cycle for easier merging: */
#define rdtscll(now) do { (now) = rdtsc_ordered(); } while (0)

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 24e4d45..e7e4804 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -26,6 +26,7 @@ struct vsyscall_gtod_data {
u64 raw_mask;
u32 raw_mult;
u32 raw_shift;
+ u32 has_rdtscp;

/* open coded 'struct timespec' */
u64 wall_time_snsec;
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