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Tue, 14 May 2019 10:26:50 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x4EAPYwj130365; Tue, 14 May 2019 10:26:50 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 2se0tw2na5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 May 2019 10:26:50 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x4EAQlqh024795; Tue, 14 May 2019 10:26:47 GMT Received: from [10.166.106.34] (/10.166.106.34) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 14 May 2019 03:26:47 -0700 Subject: Re: [RFC KVM 19/27] kvm/isolation: initialize the KVM page table with core mappings From: Alexandre Chartre To: Dave Hansen , pbonzini@redhat.com, rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, kvm@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, liran.alon@oracle.com, jwadams@google.com References: <1557758315-12667-1-git-send-email-alexandre.chartre@oracle.com> <1557758315-12667-20-git-send-email-alexandre.chartre@oracle.com> <463b86c8-e9a0-fc13-efa4-31df3aea8e54@oracle.com> Organization: Oracle Corporation Message-ID: Date: Tue, 14 May 2019 12:26:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <463b86c8-e9a0-fc13-efa4-31df3aea8e54@oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9256 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905140076 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9256 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905140076 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/13/19 6:47 PM, Alexandre Chartre wrote: > > > On 5/13/19 5:50 PM, Dave Hansen wrote: >>> +    /* >>> +     * Copy the mapping for all the kernel text. We copy at the PMD >>> +     * level since the PUD is shared with the module mapping space. >>> +     */ >>> +    rv = kvm_copy_mapping((void *)__START_KERNEL_map, KERNEL_IMAGE_SIZE, >>> +         PGT_LEVEL_PMD); >>> +    if (rv) >>> +        goto out_uninit_page_table; >> >> Could you double-check this?  We (I) have had some repeated confusion >> with the PTI code and kernel text vs. kernel data vs. __init. >> KERNEL_IMAGE_SIZE looks to be 512MB which is quite a bit bigger than >> kernel text. > > I probably have the same confusion :-) but I will try to check again. > > mm.txt says that kernel text is 512MB, and that's probably why I used KERNEL_IMAGE_SIZE. https://www.kernel.org/doc/Documentation/x86/x86_64/mm.txt ======================================================================================================================== Start addr | Offset | End addr | Size | VM area description ======================================================================================================================== [...] ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0 [...] However, vmlinux.lds.S does: . = ASSERT((_end - _text <= KERNEL_IMAGE_SIZE), "kernel image bigger than KERNEL_IMAGE_SIZE"); So this covers everything between _text and _end, which includes text, data, init and other stuff The end of the text section is tagged with _etext. So the text section is effectively (_etext - _text). This matches with what efi_setup_page_tables() used to copy kernel text: int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) { [...] npages = (_etext - _text) >> PAGE_SHIFT; text = __pa(_text); pfn = text >> PAGE_SHIFT; pf = _PAGE_RW | _PAGE_ENC; if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, pf)) { pr_err("Failed to map kernel text 1:1\n"); return 1; } [...] } alex.