Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <0790131c-95af-676f-c475-addd1191eacd@amd.com>
Date:   Mon, 11 Apr 2022 17:31:09 +0530
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.3.2
Cc:     pbonzini@redhat.com, vkuznets@redhat.com, wanpengli@tencent.com,
        jmattson@google.com, joro@8bytes.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, shauh@kernel.org, yang.zhong@intel.com,
        drjones@redhat.com, ricarkol@google.com, aaronlewis@google.com,
        wei.w.wang@intel.com, kirill.shutemov@linux.intel.com,
        corbet@lwn.net, hughd@google.com, jlayton@kernel.org,
        bfields@fieldses.org, akpm@linux-foundation.org,
        chao.p.peng@linux.intel.com, yu.c.zhang@linux.intel.com,
        jun.nakajima@intel.com, dave.hansen@intel.com,
        michael.roth@amd.com, qperret@google.com, steven.price@arm.com,
        ak@linux.intel.com, david@redhat.com, luto@kernel.org,
        vbabka@suse.cz, marcorr@google.com, erdemaktas@google.com,
        pgonda@google.com, seanjc@google.com, diviness@google.com
Subject: Re: [RFC V1 PATCH 0/5] selftests: KVM: selftests for fd-based
 approach of supporting private memory
Content-Language: en-US
To:     Vishal Annapurve <vannapurve@google.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org
References: <20220408210545.3915712-1-vannapurve@google.com>
From:   "Nikunj A. Dadhania" <nikunj@amd.com>
In-Reply-To: <20220408210545.3915712-1-vannapurve@google.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?QWxIa3J0WUtBTzVBZVJoUDJtS25kV1BuMFFLdlhmVGxUOW9oOVo3cWJUYUQ0?=
 =?utf-8?B?NkRLS01Mdm93aXJBSGZOQWpDUXo2L29wc2NjRGRGbmY1NU5OaEdhWkVGUGFi?=
 =?utf-8?B?UFhaa2JaNm9QK1c3djcwS3IwdEFJcmJyWnNOK2NlYm4zQVhiWCthWlo3b3Bm?=
 =?utf-8?B?QXJnTEpNR08rM1BZYkMwMVNXT3JyOEhsQkZvM2p0ZWM0dVlMQ3hpRmp2QUJG?=
 =?utf-8?B?N0lQSUgwTjgzZWFCb1gzeHdiT0xibkNwdDRRRnZuUmdSeW4xSllDN2svUVM1?=
 =?utf-8?B?MEw0MDBVdzI5SUVRQVVsd0x3K3FDT0ZEcy9XeFFUb3pHa1pPejkzbHV3RXpa?=
 =?utf-8?B?NGJmWnd2VmRhTlNacEVMMFB2dW55T1VITjZFbzdOR0ZXTklZeVVqREtvYnQy?=
 =?utf-8?B?dHhkcDFFQURRSCtGTStNVHJ3S3RWbmcvMys2K3lZTTd3VGk3Q3JPcTE0TEFz?=
 =?utf-8?B?ZTh4RlNlQVBFUTYydVRvRlMxODIvR2ovSTRWejJlTld2RFVJbjhZZUlxdEQz?=
 =?utf-8?B?SG8veWt2Y29PdVhNYmc3ejV4RFBQODhUOFVFcEJEb2JISENzZ0c2anQ2MDgw?=
 =?utf-8?B?NGdsdDg4eS80ZHl2dkEyM0p2ZkFSS0NvR1BCc0hIS1N3WXdxdFVNYmxoMlFP?=
 =?utf-8?B?TmN3QUkzSk4zQ2RnTHZDTWZ4bmtVNGR6b1BjOEYwaUVVcjFpaDNvVlYyVVgy?=
 =?utf-8?B?eG5uaExEZzZHWkR5ZndGeGZEV0JVUnBUSmZQT3RkdTF4cHlRSWZNNDNCOUtC?=
 =?utf-8?B?Y0dEMGg3R0Jub3ZKd1BXcndBSFZ0K0VkbEQ0eWFhZzBCT1hpenlKeTlVMlR0?=
 =?utf-8?B?S2FqZ1JQNXpPSDk4cjRKekRqczFYOTdoWWVqNVdYandQZnE1YWRiRUl5UDFR?=
 =?utf-8?B?bFpRdGVOYUpublFabSsxRnF1QlBCQWJ3RzVEYTVpeE5oUjB2ZHJ1SHFCY1dJ?=
 =?utf-8?B?c2NwUFluYU1KMytPY3RSR3NSclhjMTVoMysxbHl2enlPdlZSaVMva0x6c3Jv?=
 =?utf-8?B?MVpXV0F5VFFFTUpBbjRCQXA3Qmc5dklKeEtFTUxzZllQTEs0em9rdkFVVHVJ?=
 =?utf-8?B?UkEvVHdHNVI5VDJQV3VIdWYwSXhEZ1g4TG9lRWZmbTJ1NHVaZWZXaGprR29n?=
 =?utf-8?B?U2lQYlRVMndCMEFqM3cyUUpwNUluYVRla0tkeEc5UFJiYTA2UCtBK2lNU0lR?=
 =?utf-8?B?NG15R0NTVnVGS1pIMzZIOGE5U3ZoMngzbGI1Rlc1WTlwRC9adFJ5NXpIb1Iy?=
 =?utf-8?B?OWpaT0VmeUxCeEtSbnZQRVlZcHI5cGpBWWtDQjNOZ2twTzVDSDdzVGtMWUg5?=
 =?utf-8?B?S29GZlNwa2pROFpTVUJzQjdRUkVpOFFqbW5sMThFNHFtUTFsZFRMZENXWWNN?=
 =?utf-8?B?alVQTWJlRHNTVGdlMW1PR0FFcFBwRUw5Q0dZR2tHMkRjMUdLN3lYdHRxQXBO?=
 =?utf-8?B?MEVCZlVzQjB0Nnc2bHErc0RmYnhDbGJ2NFFRVHJxTkxLWWlRN1FqVFl6S3ND?=
 =?utf-8?B?RTdSKzZLeEpzNGYzYTJPTFRwZ0RmVWROajI0ZTdmREUvRTNqVGh0TzZJUStE?=
 =?utf-8?B?VTJIY3E0WHFPa2M0eEdmUUpsOC85eHNMcHNwaDlLbDd0V1UvWFFydWtUbHZJ?=
 =?utf-8?B?aHVZcGVac25lK3FuQTlFMkpVNXBQY1l2UUhuaFkzK2xFYW9oOEhmUmsxWkl2?=
 =?utf-8?B?Z0NlSEd5bVByek0zc2NoaFhpeFRtNlNsa3JEMGc4NmdoUVhGbmFKalpwQ0xF?=
 =?utf-8?B?Zkx5cDFGajBQNUh6aHRleCtKQVBnZ2tvcko4RkxHaDN1SFExUHFCR1BLUGNU?=
 =?utf-8?B?TU02WkdQNk1NVjhJL0lPSHZFWlUvWEZFS2NrOU9KRjBnQWI5Ri8vZnZuWGhn?=
 =?utf-8?B?Uk1DMzhocUhoeWI3TFNhKytlbmRIS2lEVTNMdlBmNzJoZ2tmR2FCU2c4OWhS?=
 =?utf-8?B?aHRkcDdNZ1lQYUtsUmV0dVdSSTUyUUhrbzV6YXZhN0hGclRZakJzdnU1alJL?=
 =?utf-8?B?ems3bW1xVm1BSEZRWE55UnFQS2kwaVFQcU5rQVMzV2d6ckxtNnN1aVY1NUYv?=
 =?utf-8?B?MHZ1WU5EeGpscWFFYzJpUFBqWHNrRDVZWWRnWktLalcyWS81UjRGR3RPTmsx?=
 =?utf-8?B?eGFxKzM4clNBZ1c4cmVLRFdJNExGMHQ5OXZMeDh3UUFVeDN6UllSbEFCKzJw?=
 =?utf-8?B?MDVSVlBDNjRzakNaM3VRelVZNFBiTHN4bFBXRXlSemNvaEFwQ1hiNnB4SjBu?=
 =?utf-8?B?bFdBYmRtcWhWTVpIS0tzRm5LcW5kaXN5aDlBOFI4Q2xSTElySlo3VXZPOWJD?=
 =?utf-8?B?R2xrZTBwY1VEWnEwQ0tleTFHNENjT1I2QzhObmM4WW5nOTdqU2lQQT09?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 5cb220a0-3729-477e-b6eb-08da1bb30c96
X-MS-Exchange-CrossTenant-AuthSource: DM5PR12MB2470.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Apr 2022 12:01:45.6895
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 30oiMyxoNGXZLxwbGkIpJMpKD3KFhx6rKqyQMJozjz/Da1LppfsDXpHnGG0PfK5xSlyx+92K2LnXPzjsPpOHgg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR12MB1844
X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,NICE_REPLY_A,RDNS_NONE,SPF_HELO_NONE,
	T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no
	version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 4/9/2022 2:35 AM, Vishal Annapurve wrote:
> This series implements selftests targeting the feature floated by Chao
> via:
> https://lore.kernel.org/linux-mm/20220310140911.50924-1-chao.p.peng@linux.intel.com/
> 

Thanks for working on this.

> Below changes aim to test the fd based approach for guest private memory
> in context of normal (non-confidential) VMs executing on non-confidential
> platforms.
> 
> Confidential platforms along with the confidentiality aware software
> stack support a notion of private/shared accesses from the confidential
> VMs.
> Generally, a bit in the GPA conveys the shared/private-ness of the
> access. Non-confidential platforms don't have a notion of private or
> shared accesses from the guest VMs. To support this notion,
> KVM_HC_MAP_GPA_RANGE
> is modified to allow marking an access from a VM within a GPA range as
> always shared or private. Any suggestions regarding implementing this ioctl
> alternatively/cleanly are appreciated.
> 
> priv_memfd_test.c file adds a suite of two basic selftests to access private
> memory from the guest via private/shared access and checking if the contents
> can be leaked to/accessed by vmm via shared memory view.
> 
> Test results:
> 1) PMPAT - PrivateMemoryPrivateAccess test passes
> 2) PMSAT - PrivateMemorySharedAccess test fails currently and needs more
> analysis to understand the reason of failure.

That could be because of the return code (*r = -1) from the KVM_EXIT_MEMORY_ERROR. 
This gets interpreted as -EPERM in the VMM when the vcpu_run exits.

	+	vcpu->run->exit_reason = KVM_EXIT_MEMORY_ERROR;
	+	vcpu->run->memory.flags = flags;
	+	vcpu->run->memory.padding = 0;
	+	vcpu->run->memory.gpa = fault->gfn << PAGE_SHIFT;
	+	vcpu->run->memory.size = PAGE_SIZE;
	+	fault->pfn = -1;
	+	*r = -1;
	+	return true;


Regards
Nikunj

[1] https://lore.kernel.org/all/20220310140911.50924-10-chao.p.peng@linux.intel.com/#t