From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81261C2BC61 for ; Tue, 30 Oct 2018 05:35:46 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C3E6B20664 for ; Tue, 30 Oct 2018 05:35:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=ozlabs.org header.i=@ozlabs.org header.b="h2ExxK/k" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C3E6B20664 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ozlabs.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 42kgDH5kv0zF1Q0 for ; Tue, 30 Oct 2018 16:35:43 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.org Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=ozlabs.org header.i=@ozlabs.org header.b="h2ExxK/k"; dkim-atps=neutral Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42kg721td6zDrPy for ; Tue, 30 Oct 2018 16:31:10 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=ozlabs.org header.i=@ozlabs.org header.b="h2ExxK/k"; dkim-atps=neutral Received: by ozlabs.org (Postfix, from userid 1003) id 42kg716Zqpz9s5c; Tue, 30 Oct 2018 16:31:09 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ozlabs.org; s=201707; t=1540877469; bh=xd9ydww8gS29Rw1cBwuvThzBA7hOWHhPVkHqbT5SIsY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=h2ExxK/kHtA1O0hXERTk6wuIwBQ29R3ytACygD7W80LlBTzXj1+4mnnQemQhycsOs TzYTRj9B74ejT9g7TBvZW9em+6ohjKha5d+YhNTtrvmy3buHXUduimaRWwU0mG32VC R7kv2scxWseBLbiCsvn+OqjIon7J5igYnVk7UQksLIUZxLLhPyaWkvGLw0wK+IJqev kvGcGxXs784v5B+fVkMvW9pVZa9s4CivAOXD1F3AedeytaB/9LXxwm6vYDHAZy4Gkt tpT7w+6rz78PK8tha0R1usY08oYKNyM6tzvja+i36GTvC58jrbEDRt0xZRUV6MnnDZ 5a9K4emqQ8fNg== Date: Tue, 30 Oct 2018 16:26:46 +1100 From: Paul Mackerras To: Bharata B Rao Subject: Re: [RFC PATCH v1 2/4] kvmppc: Add support for shared pages in HMM driver Message-ID: <20181030052646.GB11072@blackberry> References: <20181022051837.1165-1-bharata@linux.ibm.com> <20181022051837.1165-3-bharata@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181022051837.1165-3-bharata@linux.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxram@us.ibm.com, kvm-ppc@vger.kernel.org, benh@linux.ibm.com, linux-mm@kvack.org, jglisse@redhat.com, aneesh.kumar@linux.vnet.ibm.com, paulus@au1.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Oct 22, 2018 at 10:48:35AM +0530, Bharata B Rao wrote: > A secure guest will share some of its pages with hypervisor (Eg. virtio > bounce buffers etc). Support shared pages in HMM driver. > > Signed-off-by: Bharata B Rao Comments below... > --- > arch/powerpc/kvm/book3s_hv_hmm.c | 69 ++++++++++++++++++++++++++++++-- > 1 file changed, 65 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv_hmm.c b/arch/powerpc/kvm/book3s_hv_hmm.c > index a2ee3163a312..09b8e19b7605 100644 > --- a/arch/powerpc/kvm/book3s_hv_hmm.c > +++ b/arch/powerpc/kvm/book3s_hv_hmm.c > @@ -50,6 +50,7 @@ struct kvmppc_hmm_page_pvt { > struct hlist_head *hmm_hash; > unsigned int lpid; > unsigned long gpa; > + bool skip_page_out; > }; > > struct kvmppc_hmm_migrate_args { > @@ -278,6 +279,65 @@ static unsigned long kvmppc_gpa_to_hva(struct kvm *kvm, unsigned long gpa, > return hva; > } > > +/* > + * Shares the page with HV, thus making it a normal page. > + * > + * - If the page is already secure, then provision a new page and share > + * - If the page is a normal page, share the existing page > + * > + * In the former case, uses the HMM fault handler to release the HMM page. > + */ > +static unsigned long > +kvmppc_share_page(struct kvm *kvm, unsigned long gpa, > + unsigned long addr, unsigned long page_shift) > +{ > + > + int ret; > + struct hlist_head *list, *hmm_hash; > + unsigned int lpid = kvm->arch.lpid; > + unsigned long flags; > + struct kvmppc_hmm_pfn_entry *p; > + struct page *hmm_page, *page; > + struct kvmppc_hmm_page_pvt *pvt; > + unsigned long pfn; > + > + /* > + * First check if the requested page has already been given to > + * UV as a secure page. If so, ensure that we don't issue a > + * UV_PAGE_OUT but instead directly send the page > + */ > + spin_lock_irqsave(&kvmppc_hmm_lock, flags); > + hmm_hash = kvm->arch.hmm_hash; > + list = &hmm_hash[kvmppc_hmm_pfn_hash_fn(gpa)]; > + hlist_for_each_entry(p, list, hlist) { > + if (p->addr == gpa) { > + hmm_page = pfn_to_page(p->hmm_pfn); > + get_page(hmm_page); /* TODO: Necessary ? */ > + pvt = (struct kvmppc_hmm_page_pvt *) > + hmm_devmem_page_get_drvdata(hmm_page); > + pvt->skip_page_out = true; > + put_page(hmm_page); > + break; > + } > + } > + spin_unlock_irqrestore(&kvmppc_hmm_lock, flags); > + > + ret = get_user_pages_fast(addr, 1, 0, &page); Why are we calling this with write==0? Surely in general the secure guest will expect to be able to write to the shared page? Also, in general get_user_pages_fast isn't sufficient to translate a host virtual address (derived from a guest real address) into a pfn. See for example hva_to_pfn() in virt/kvm/kvm_main.c and the things it does to cope with the various cases that one can hit. I can imagine in future that the secure guest might want to establish a shared mapping to a PCI device, for instance. > + if (ret != 1) > + return H_PARAMETER; > + > + pfn = page_to_pfn(page); > + if (is_zero_pfn(pfn)) { > + put_page(page); > + return H_SUCCESS; > + } The ultravisor still needs a page to map into the guest in this case, doesn't it? What's the point of returning without giving the ultravisor a page to use? > + > + ret = uv_page_in(lpid, pfn << page_shift, gpa, 0, page_shift); > + put_page(page); > + > + return (ret == U_SUCCESS) ? H_SUCCESS : H_PARAMETER; > +} > + > /* > * Move page from normal memory to secure memory. > */ > @@ -300,8 +360,8 @@ kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa, > return H_PARAMETER; > end = addr + (1UL << page_shift); > > - if (flags) > - return H_P2; > + if (flags & H_PAGE_IN_SHARED) > + return kvmppc_share_page(kvm, gpa, addr, page_shift); Would be best to fail if any unknown flags are set, I would think. > > args.hmm_hash = kvm->arch.hmm_hash; > args.lpid = kvm->arch.lpid; > @@ -349,8 +409,9 @@ kvmppc_hmm_fault_migrate_alloc_and_copy(struct vm_area_struct *vma, > hmm_devmem_page_get_drvdata(spage); > > pfn = page_to_pfn(dpage); > - ret = uv_page_out(pvt->lpid, pfn << PAGE_SHIFT, > - pvt->gpa, 0, PAGE_SHIFT); > + if (!pvt->skip_page_out) > + ret = uv_page_out(pvt->lpid, pfn << PAGE_SHIFT, > + pvt->gpa, 0, PAGE_SHIFT); > if (ret == U_SUCCESS) > *dst_pfn = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED; > } > -- > 2.17.1 Paul.