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target-i386: add RDTSCP support

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RDTSCP reads the time stamp counter and atomically also the content
of a 32-bit MSR, which can be freely set by the OS. This allows CPU
local data to be queried by userspace.
Linux uses this to allow a fast implementation of the getcpu()
syscall, which uses the vsyscall page to avoid a context switch.
AMD CPUs since K8RevF and Intel CPUs since Nehalem support this
instruction.
RDTSCP is guarded by the RDTSCP CPUID bit (Fn8000_0001:EDX[27]).

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Andre Przywara 2009-09-19 00:30:49 +02:00 • committed by Aurelien Jarno
parent d9f4bb27db
commit 1b050077d2
5 changed files with 65 additions and 18 deletions
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1
target-i386/helper.h
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@ -80,6 +80,7 @@ DEF_HELPER_1(cmpxchg16b, void, tl)
DEF_HELPER_0(single_step, void)
DEF_HELPER_0(cpuid, void)
DEF_HELPER_0(rdtsc, void)
DEF_HELPER_0(rdtscp, void)
DEF_HELPER_0(rdpmc, void)
DEF_HELPER_0(rdmsr, void)
DEF_HELPER_0(wrmsr, void)