From: Xu Yihang Date: Tue, 23 Mar 2021 02:43:02 +0000 (+0800) Subject: x86/hyperv: Fix unused variable 'msr_val' warning in hv_qlock_wait X-Git-Tag: v5.13-rc1~178^2~14 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=13c4d4626a4b205e496eb65d6316a3dcb89a7d62;p=thirdparty%2Fkernel%2Flinux.git x86/hyperv: Fix unused variable 'msr_val' warning in hv_qlock_wait Fixes the following W=1 kernel build warning(s): arch/x86/hyperv/hv_spinlock.c:28:16: warning: variable ‘msr_val’ set but not used [-Wunused-but-set-variable] unsigned long msr_val; As Hypervisor Top-Level Functional Specification states in chapter 7.5 Virtual Processor Idle Sleep State, "A partition which possesses the AccessGuestIdleMsr privilege (refer to section 4.2.2) may trigger entry into the virtual processor idle sleep state through a read to the hypervisor-defined MSR HV_X64_MSR_GUEST_IDLE". That means only a read of the MSR is necessary. The returned value msr_val is not used. Cast it to void to silence this warning. Reference: https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs Reported-by: Hulk Robot Signed-off-by: Xu Yihang Link: https://lore.kernel.org/r/20210323024302.174434-1-xuyihang@huawei.com Signed-off-by: Wei Liu --- diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c index f3270c1fc48c1..91cfe698bde0c 100644 --- a/arch/x86/hyperv/hv_spinlock.c +++ b/arch/x86/hyperv/hv_spinlock.c @@ -25,7 +25,6 @@ static void hv_qlock_kick(int cpu) static void hv_qlock_wait(u8 *byte, u8 val) { - unsigned long msr_val; unsigned long flags; if (in_nmi()) @@ -48,8 +47,13 @@ static void hv_qlock_wait(u8 *byte, u8 val) /* * Only issue the rdmsrl() when the lock state has not changed. */ - if (READ_ONCE(*byte) == val) + if (READ_ONCE(*byte) == val) { + unsigned long msr_val; + rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val); + + (void)msr_val; + } local_irq_restore(flags); }