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| author | Andrew Cooper <andrew.cooper3@citrix.com> | 2024-08-22 00:39:05 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-08-25 19:23:00 +0200 |
| commit | efe508816d2caf83536ff2f308e09043380fb2b7 (patch) | |
| tree | 23bddf21cd6629fdb537875fa348a32454dd0dce /arch/x86/include/asm/switch_to.h | |
| parent | 0dfac6f267fa091aa348c6a6742b463c9e7c98e3 (diff) | |
| download | linux-efe508816d2caf83536ff2f308e09043380fb2b7.tar.gz linux-efe508816d2caf83536ff2f308e09043380fb2b7.tar.bz2 linux-efe508816d2caf83536ff2f308e09043380fb2b7.zip | |
x86/msr: Switch between WRMSRNS and WRMSR with the alternatives mechanism
Per the discussion about FRED MSR writes with WRMSRNS instruction [1],
use the alternatives mechanism to choose WRMSRNS when it's available,
otherwise fallback to WRMSR.
Remove the dependency on X86_FEATURE_WRMSRNS as WRMSRNS is no longer
dependent on FRED.
[1] https://lore.kernel.org/lkml/15f56e6a-6edd-43d0-8e83-bb6430096514@citrix.com/
Use DS prefix to pad WRMSR instead of a NOP. The prefix is ignored. At
least that's the current information from the hardware folks.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240822073906.2176342-3-xin@zytor.com
Diffstat (limited to 'arch/x86/include/asm/switch_to.h')
| -rw-r--r-- | arch/x86/include/asm/switch_to.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index c3bd0c0758c9..e9ded149a9e3 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -71,7 +71,6 @@ static inline void update_task_stack(struct task_struct *task) this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); #else if (cpu_feature_enabled(X86_FEATURE_FRED)) { - /* WRMSRNS is a baseline feature for FRED. */ wrmsrns(MSR_IA32_FRED_RSP0, (unsigned long)task_stack_page(task) + THREAD_SIZE); } else if (cpu_feature_enabled(X86_FEATURE_XENPV)) { /* Xen PV enters the kernel on the thread stack. */ |