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Date:      Tue, 12 Oct 2021 16:01:42 GMT
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org
Subject:   git: 946f96d13b01 - stable/12 - x86: cpufunc: Add rdtsc_ordered()
Message-ID:  <202110121601.19CG1ggj074155@gitrepo.freebsd.org>

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The branch stable/12 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=946f96d13b013963cc11de1eca2ede4c0658fc61

commit 946f96d13b013963cc11de1eca2ede4c0658fc61
Author:     Adam Fenn <adam@fenn.io>
AuthorDate: 2021-07-28 17:12:00 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2021-10-12 16:01:26 +0000

    x86: cpufunc: Add rdtsc_ordered()
    
    Add a variant of 'rdtsc()' that performs the ordered version of 'rdtsc'
    appropriate for the invoking x86 variant.
    
    Also, expose the 'lfence'-ed and 'mfence'-ed 'rdtsc()' variants needed
    by 'rdtsc_ordered()' for general use.
    
    Sponsored by:   Juniper Networks, Inc.
    Sponsored by:   Klara, Inc.
    Reviewed by:    kib
    Differential Revision:  https://reviews.freebsd.org/D31416
    
    (cherry picked from commit 652ae7b11485d9f991ea66a56aa79d4dd9cd1103)
---
 sys/amd64/include/cpufunc.h | 14 ++++++++++++++
 sys/i386/include/cpufunc.h  | 14 ++++++++++++++
 sys/x86/include/x86_var.h   |  1 +
 sys/x86/x86/cpu_machdep.c   | 16 ++++++++++++++++
 4 files changed, 45 insertions(+)

diff --git a/sys/amd64/include/cpufunc.h b/sys/amd64/include/cpufunc.h
index 93e62c0df73a..95086469d51d 100644
--- a/sys/amd64/include/cpufunc.h
+++ b/sys/amd64/include/cpufunc.h
@@ -394,6 +394,20 @@ rdtsc(void)
 	return (low | ((uint64_t)high << 32));
 }
 
+static __inline uint64_t
+rdtsc_ordered_lfence(void)
+{
+	lfence();
+	return (rdtsc());
+}
+
+static __inline uint64_t
+rdtsc_ordered_mfence(void)
+{
+	mfence();
+	return (rdtsc());
+}
+
 static __inline uint64_t
 rdtscp(void)
 {
diff --git a/sys/i386/include/cpufunc.h b/sys/i386/include/cpufunc.h
index 7b99978facc3..79cdd3004b77 100644
--- a/sys/i386/include/cpufunc.h
+++ b/sys/i386/include/cpufunc.h
@@ -394,6 +394,20 @@ rdtsc(void)
 	return (rv);
 }
 
+static __inline uint64_t
+rdtsc_ordered_lfence(void)
+{
+	lfence();
+	return (rdtsc());
+}
+
+static __inline uint64_t
+rdtsc_ordered_mfence(void)
+{
+	mfence();
+	return (rdtsc());
+}
+
 static __inline uint64_t
 rdtscp(void)
 {
diff --git a/sys/x86/include/x86_var.h b/sys/x86/include/x86_var.h
index 3e146b44338f..5b8e41bd76d7 100644
--- a/sys/x86/include/x86_var.h
+++ b/sys/x86/include/x86_var.h
@@ -159,6 +159,7 @@ int	pti_get_default(void);
 int	user_dbreg_trap(register_t dr6);
 int	minidumpsys(struct dumperinfo *);
 struct pcb *get_pcb_td(struct thread *td);
+uint64_t rdtsc_ordered(void);
 
 #define	MSR_OP_ANDNOT		0x00000001
 #define	MSR_OP_OR		0x00000002
diff --git a/sys/x86/x86/cpu_machdep.c b/sys/x86/x86/cpu_machdep.c
index 8bceaee913db..26423228d5dc 100644
--- a/sys/x86/x86/cpu_machdep.c
+++ b/sys/x86/x86/cpu_machdep.c
@@ -76,6 +76,7 @@ __FBSDID("$FreeBSD$");
 
 #include <machine/clock.h>
 #include <machine/cpu.h>
+#include <machine/cpufunc.h>
 #include <machine/cputypes.h>
 #include <machine/specialreg.h>
 #include <machine/md_var.h>
@@ -88,6 +89,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/elan_mmcr.h>
 #endif
 #include <x86/acpica_machdep.h>
+#include <x86/ifunc.h>
 
 #include <vm/vm.h>
 #include <vm/vm_extern.h>
@@ -1421,3 +1423,17 @@ acpi_get_fadt_bootflags(uint16_t *flagsp)
 	return (false);
 #endif
 }
+
+DEFINE_IFUNC(, uint64_t, rdtsc_ordered, (void), static)
+{
+	bool cpu_is_amd = cpu_vendor_id == CPU_VENDOR_AMD ||
+	    cpu_vendor_id == CPU_VENDOR_HYGON;
+
+	if ((amd_feature & AMDID_RDTSCP) != 0)
+		return (rdtscp);
+	else if ((cpu_feature & CPUID_SSE2) != 0)
+		return (cpu_is_amd ? rdtsc_ordered_mfence :
+		    rdtsc_ordered_lfence);
+	else
+		return (rdtsc);
+}



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