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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id j13-20020a170902da8d00b0015e8d4eb260sm5388000plx.170.2022.05.23.10.37.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 May 2022 10:37:23 -0700 (PDT) Date: Mon, 23 May 2022 17:37:20 +0000 From: Sean Christopherson To: Mingwei Zhang Cc: David Matlack , Paolo Bonzini , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Jones , Ben Gardon , Peter Xu , maciej.szmigiero@oracle.com, "moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" , "open list:KERNEL VIRTUAL MACHINE FOR MIPS (KVM/mips)" , "open list:KERNEL VIRTUAL MACHINE FOR MIPS (KVM/mips)" , "open list:KERNEL VIRTUAL MACHINE FOR RISC-V (KVM/riscv)" , Peter Feiner , Lai Jiangshan Subject: Re: [PATCH v6 21/22] KVM: Allow for different capacities in kvm_mmu_memory_cache structs Message-ID: References: <20220516232138.1783324-1-dmatlack@google.com> <20220516232138.1783324-22-dmatlack@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, May 20, 2022, Mingwei Zhang wrote: > On Mon, May 16, 2022 at 4:24 PM David Matlack wrote: > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index e089db822c12..5e2e75014256 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -369,14 +369,31 @@ static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc, > > return (void *)__get_free_page(gfp_flags); > > } > > > > -int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) > > +static int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min) > > { > > + gfp_t gfp = GFP_KERNEL_ACCOUNT; > > void *obj; > > > > if (mc->nobjs >= min) > > return 0; > > - while (mc->nobjs < ARRAY_SIZE(mc->objects)) { > > - obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT); > > + > > + if (unlikely(!mc->objects)) { > > + if (WARN_ON_ONCE(!capacity)) > > + return -EIO; > > + > > + mc->objects = kvmalloc_array(sizeof(void *), capacity, gfp); > > + if (!mc->objects) > > + return -ENOMEM; > > + > > + mc->capacity = capacity; > > Do we want to ensure the minimum value of the capacity? I think > otherwise, we may more likely start using memory from GFP_ATOMIC if > the capacity is less than, say 5? But the minimum value seems related > to each cache type. Eh, if we specify a minimum, just make the arch default the minimum. That way we avoid adding even more magic/arbitrary numbers. E.g. for whatever reason, MIPS's default is '4'.