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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a00c130538sm54658975e9.4.2026.09.29.01.15.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Sep 2026 01:15:07 -0700 (PDT) Date: Tue, 29 Sep 2026 09:15:06 +0100 From: David Laight To: Sean Christopherson Cc: "Peng Fan (OSS)" , Vitaly Kuznetsov , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Peng Fan , kvm@vger.kernel.org Subject: Re: [PATCH] KVM: x86: use assign_bit() where applicable Message-ID: <20260929091506.5472bc5c@pumpkin> In-Reply-To: References: <20260920022649.3145701-1-peng.fan@oss.nxp.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 28 Sep 2026 17:58:57 -0700 Sean Christopherson wrote: > On Sun, Sep 20, 2026, Peng Fan (OSS) wrote: > > From: Peng Fan > > > > 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 > > --- > > 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. > The same is pretty much true of __set_bit() and even BIT(). What is wrong with: if (synic_has_vector_auto_eoi(synic, vector)) vector |= 1u << synic->auto_eoi_bitmap; else vector &= ~(1u << synic->auto_eoi_bitmap); 'Does what is sway on the tin'. David