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Tue, 15 Aug 2023 15:30:10 -0700 (PDT) Date: Tue, 15 Aug 2023 15:30:08 -0700 In-Reply-To: <20230811045127.3308641-6-rananta@google.com> Mime-Version: 1.0 References: <20230811045127.3308641-1-rananta@google.com> <20230811045127.3308641-6-rananta@google.com> Message-ID: Subject: Re: [PATCH v9 05/14] KVM: Allow range-based TLB invalidation from common code From: Sean Christopherson To: Raghavendra Rao Ananta Cc: Oliver Upton , Marc Zyngier , James Morse , Suzuki K Poulose , Paolo Bonzini , Huacai Chen , Zenghui Yu , Anup Patel , Atish Patra , Jing Zhang , Reiji Watanabe , Colton Lewis , David Matlack , Fuad Tabba , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Gavin Shan , Shaoqin Huang X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230815_153013_037893_4029FBE9 X-CRM114-Status: GOOD ( 13.39 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Aug 11, 2023, Raghavendra Rao Ananta wrote: > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index ec169f5c7dce2..00f7bda9202f2 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -278,16 +278,14 @@ static inline bool kvm_available_flush_remote_tlbs_range(void) > return kvm_x86_ops.flush_remote_tlbs_range; > } > > -void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn, > - gfn_t nr_pages) > +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages) > { > int ret = -EOPNOTSUPP; > > if (kvm_x86_ops.flush_remote_tlbs_range) > - ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, start_gfn, > - nr_pages); > - if (ret) > - kvm_flush_remote_tlbs(kvm); > + ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages); > + > + return ret; Please write this as if (kvm_x86_ops.flush_remote_tlbs_range) return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages); return -EOPNOTSUPP; or alternatively if (!kvm_x86_ops.flush_remote_tlbs_range) return -EOPNOTSUPP; return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages); Hmm, I'll throw my official vote for the second version. The local "ret" is unnecessary and is suprisingly dangerous. I screwed up the conflict resolution when cherry-picking my CONFIG_HYPERV change to see what the conflict looked like and ended up with a double flush: int ret = -EOPNOTSUPP; if (kvm_x86_ops.flush_remote_tlbs_range) ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages); if (ret) kvm_flush_remote_tlbs(kvm); return ret; Dropping "ret" makes it much harder to get trigger happy when resolving conflicts. No need for a new version to fix the above, assuming Marc/Oliver is ok doing fixup when applying. Nit aside, looks good for x86, and I know of no conflicts, so take 'er away! Acked-by: Sean Christopherson _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel