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Fri, 18 Apr 2025 16:34:17 +0100 Date: Fri, 18 Apr 2025 16:34:24 +0100 Message-ID: <87r01pxz3z.wl-maz@kernel.org> From: Marc Zyngier To: Yury Norov Cc: Luo Jie , Rasmus Villemoes , Julia Lawall , Nicolas Palix , Catalin Marinas , Will Deacon , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , linux-kernel@vger.kernel.org, cocci@inria.fr, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, andrew@lunn.ch, quic_kkumarcs@quicinc.com, quic_linchen@quicinc.com, quic_leiwei@quicinc.com, quic_suruchia@quicinc.com, quic_pavir@quicinc.com Subject: Re: [PATCH v3 4/6] arm64: nvhe: Convert the opencoded field modify In-Reply-To: References: <20250417-field_modify-v3-0-6f7992aafcb7@quicinc.com> <20250417-field_modify-v3-4-6f7992aafcb7@quicinc.com> <86r01rjald.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: yury.norov@gmail.com, quic_luoj@quicinc.com, linux@rasmusvillemoes.dk, Julia.Lawall@inria.fr, nicolas.palix@imag.fr, catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-kernel@vger.kernel.org, cocci@inria.fr, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, andrew@lunn.ch, quic_kkumarcs@quicinc.com, quic_linchen@quicinc.com, quic_leiwei@quicinc.com, quic_suruchia@quicinc.com, quic_pavir@quicinc.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250418_083421_880491_881961F6 X-CRM114-Status: GOOD ( 24.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 18 Apr 2025 16:14:48 +0100, Yury Norov wrote: > > On Thu, Apr 17, 2025 at 12:23:10PM +0100, Marc Zyngier wrote: > > On Thu, 17 Apr 2025 11:47:11 +0100, > > Luo Jie wrote: > > > > > > Replaced below code with the wrapper FIELD_MODIFY(MASK, ®, val) > > > - reg &= ~MASK; > > > - reg |= FIELD_PREP(MASK, val); > > > The semantic patch that makes this change is available > > > in scripts/coccinelle/misc/field_modify.cocci. > > > > > > More information about semantic patching is available at > > > https://coccinelle.gitlabpages.inria.fr/website > > > > > > Signed-off-by: Luo Jie > > > --- > > > arch/arm64/kvm/hyp/include/nvhe/memory.h | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > > > index 34233d586060..b2af748964d0 100644 > > > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > > > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > > > @@ -30,8 +30,7 @@ enum pkvm_page_state { > > > static inline enum kvm_pgtable_prot pkvm_mkstate(enum kvm_pgtable_prot prot, > > > enum pkvm_page_state state) > > > { > > > - prot &= ~PKVM_PAGE_STATE_PROT_MASK; > > > - prot |= FIELD_PREP(PKVM_PAGE_STATE_PROT_MASK, state); > > > + FIELD_MODIFY(PKVM_PAGE_STATE_PROT_MASK, &prot, state); > > > return prot; > > > } > > > > Following up on my suggestion to *not* add anything new, this patch > > could be written as: > > > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > > index 34233d5860607..08cb6ba0e0716 100644 > > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > > @@ -30,9 +30,8 @@ enum pkvm_page_state { > > static inline enum kvm_pgtable_prot pkvm_mkstate(enum kvm_pgtable_prot prot, > > enum pkvm_page_state state) > > { > > - prot &= ~PKVM_PAGE_STATE_PROT_MASK; > > - prot |= FIELD_PREP(PKVM_PAGE_STATE_PROT_MASK, state); > > - return prot; > > + u64 p = prot; > > + return u64_replace_bits(p, state, PKVM_PAGE_STATE_PROT_MASK); > > } > > This is a great example where u64_replace_bit() should NOT be used. Well, I'll like well it enough. M. -- Jazz isn't dead. It just smells funny.