Re: [PATCH] KVM: x86: use assign_bit() where applicable

[Sean Christopherson <seanjc@google.com>]

On Sun, Sep 20, 2026, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@nxp.com>
> 
> Convert open-coded if/else with set_bit/clear_bit and their
> non-atomic __set_bit/__clear_bit variants to the assign_bit/__assign_bit
> API.

...

> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>  arch/x86/kvm/hyperv.c  | 12 ++++--------
>  arch/x86/kvm/svm/pmu.c |  6 ++----
>  arch/x86/kvm/x86.c     | 11 +++--------
>  3 files changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 8d2669d8ef34..c131d9a3c550 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -114,17 +114,13 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
>  	if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
>  		return;
>  
> -	if (synic_has_vector_connected(synic, vector))
> -		__set_bit(vector, synic->vec_bitmap);
> -	else
> -		__clear_bit(vector, synic->vec_bitmap);
> +	__assign_bit(vector, synic->vec_bitmap,
> +		     synic_has_vector_connected(synic, vector));
>  
>  	auto_eoi_old = !bitmap_empty(synic->auto_eoi_bitmap, 256);
>  
> -	if (synic_has_vector_auto_eoi(synic, vector))
> -		__set_bit(vector, synic->auto_eoi_bitmap);
> -	else
> -		__clear_bit(vector, synic->auto_eoi_bitmap);
> +	__assign_bit(vector, synic->auto_eoi_bitmap,
> +		     synic_has_vector_auto_eoi(synic, vector));

Am I the only one that finds the assign_bit() code signficantly harder to follow?
Maybe it's just that I haven't seen assign_bit() much, but I've come back to this
patch several times, and I've had the same reaction every time.  IMO, this is a
solution looking for a problem.