File 5d03a0c4-1-Arm-add-an-isb-before-reading-CNTPCT... of Package xen

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File 5d03a0c4-1-Arm-add-an-isb-before-reading-CNTPCT_EL0.patch of Package xen (Revision c8008d51fc7293cec12f26257bd7c446)

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# Commit 5e1b9cb0f29d6b52bd603d22bca4ae4cfeef9e74
# Date 2019-06-14 14:27:32 +0100
# Author Julien Grall <julien.grall@arm.com>
# Committer Julien Grall <julien.grall@arm.com>
xen/arm: Add an isb() before reading CNTPCT_EL0 to prevent re-ordering

Per D8.2.1 in ARM DDI 0487C.a, "a read to CNTPCT_EL0 can occur
speculatively and out of order relative to other instructions executed
on the same PE."

Add an instruction barrier to get accurate number of cycles when
requested in get_cycles(). For the other users of CNPCT_EL0, replace by
a call to get_cycles().

This is part of XSA-295.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

--- a/xen/arch/arm/time.c
+++ b/xen/arch/arm/time.c
@@ -151,7 +151,7 @@ void __init preinit_xen_time(void)
     if ( res )
         panic("Timer: Cannot initialize platform timer\n");
 
-    boot_count = READ_SYSREG64(CNTPCT_EL0);
+    boot_count = get_cycles();
 }
 
 static void __init init_dt_xen_time(void)
@@ -192,7 +192,7 @@ int __init init_xen_time(void)
 /* Return number of nanoseconds since boot */
 s_time_t get_s_time(void)
 {
-    uint64_t ticks = READ_SYSREG64(CNTPCT_EL0) - boot_count;
+    uint64_t ticks = get_cycles() - boot_count;
     return ticks_to_ns(ticks);
 }
 
--- a/xen/include/asm-arm/time.h
+++ b/xen/include/asm-arm/time.h
@@ -2,6 +2,7 @@
 #define __ARM_TIME_H__
 
 #include <asm/sysregs.h>
+#include <asm/system.h>
 
 #define DT_MATCH_TIMER                      \
     DT_MATCH_COMPATIBLE("arm,armv7-timer"), \
@@ -11,6 +12,7 @@ typedef uint64_t cycles_t;
 
 static inline cycles_t get_cycles (void)
 {
+        isb();
         return READ_SYSREG64(CNTPCT_EL0);
 }

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File 5d03a0c4-1-Arm-add-an-isb-before-reading-CNTPCT_EL0.patch of Package xen (Revision c8008d51fc7293cec12f26257bd7c446)

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