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Thu, 03 Sep 2020 20:59:50 -0400 X-MC-Unique: c44Z_jsvPI-oFkILqi6vEA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C921E81F035; Fri, 4 Sep 2020 00:59:48 +0000 (UTC) Received: from [10.64.54.159] (vpn2-54-159.bne.redhat.com [10.64.54.159]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 51B1978B38; Fri, 4 Sep 2020 00:59:46 +0000 (UTC) Subject: Re: [PATCH v3 20/21] KVM: arm64: Remove unused 'pgd' field from 'struct kvm_s2_mmu' To: Will Deacon References: <20200825093953.26493-1-will@kernel.org> <20200825093953.26493-21-will@kernel.org> <20200903165020.GC7791@willie-the-truck> From: Gavin Shan Message-ID: <7911796d-9124-cb7c-ace5-51e3b6d2dc28@redhat.com> Date: Fri, 4 Sep 2020 10:59:44 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20200903165020.GC7791@willie-the-truck> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=gshan@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200903_205953_602199_4004A3D8 X-CRM114-Status: GOOD ( 20.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Gavin Shan Cc: Suzuki Poulose , Marc Zyngier , Quentin Perret , James Morse , Catalin Marinas , kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Will, On 9/4/20 2:50 AM, Will Deacon wrote: > On Thu, Sep 03, 2020 at 03:07:17PM +1000, Gavin Shan wrote: >> On 8/25/20 7:39 PM, Will Deacon wrote: >>> The stage-2 page-tables are entirely encapsulated by the 'pgt' field of >>> 'struct kvm_s2_mmu', so remove the unused 'pgd' field. >>> >>> Cc: Marc Zyngier >>> Cc: Quentin Perret >>> Signed-off-by: Will Deacon >>> --- >>> arch/arm64/include/asm/kvm_host.h | 1 - >>> arch/arm64/kvm/mmu.c | 2 -- >>> 2 files changed, 3 deletions(-) >>> >> >> I think this might be folded into PATCH[18] as both patches are >> simple enough. I'm not sure the changes introduced in PATCH[19] >> prevent us doing this. >> >> There is another question below. >> >> Reviewed-by: Gavin Shan >> >>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>> index 0b7c702b2151..41caf29bd93c 100644 >>> --- a/arch/arm64/include/asm/kvm_host.h >>> +++ b/arch/arm64/include/asm/kvm_host.h >>> @@ -79,7 +79,6 @@ struct kvm_s2_mmu { >>> * for vEL1/EL0 with vHCR_EL2.VM == 0. In that case, we use the >>> * canonical stage-2 page tables. >>> */ >>> - pgd_t *pgd; >>> phys_addr_t pgd_phys; >>> struct kvm_pgtable *pgt; >>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c >>> index ddeec0b03666..f28e03dcb897 100644 >>> --- a/arch/arm64/kvm/mmu.c >>> +++ b/arch/arm64/kvm/mmu.c >>> @@ -384,7 +384,6 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu) >>> mmu->kvm = kvm; >>> mmu->pgt = pgt; >>> mmu->pgd_phys = __pa(pgt->pgd); >>> - mmu->pgd = (void *)pgt->pgd; >>> mmu->vmid.vmid_gen = 0; >>> return 0; >>> @@ -470,7 +469,6 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) >>> spin_lock(&kvm->mmu_lock); >>> pgt = mmu->pgt; >>> if (pgt) { >>> - mmu->pgd = NULL; >>> mmu->pgd_phys = 0; >>> mmu->pgt = NULL; >>> free_percpu(mmu->last_vcpu_ran); >>> >> >> I guess mmu->pgd_phys might be removed either because kvm_get_vttbr() >> is the only consumer. > > Hmm, but kvm_get_vttbr() is still used after these patches, so I think > the pgd_phys field needs to stick around. > Yes, kvm_get_vttbr() is the only consumer. The corresponding physical address can be figured out in the function, we needn't have the physical address and cache it in advance. However, it's not a big deal. I probably post one patch to remove it after this series gets merged. baddr = __pa(mmu->pgt->pgd); Thanks, Gavin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel