Received-SPF: pass (google.com: domain of linux-kernel+bounces-202373-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Message-ID: <fc6a2fb6-4762-4d5b-aa65-8588914221ce@amd.com>
Date: Wed, 5 Jun 2024 17:22:55 +0530
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] KVM: SNP: Fix LBR Virtualization for SNP guest
Content-Language: en-US
To: Ravi Bangoria <ravi.bangoria@amd.com>, seanjc@google.com,
 pbonzini@redhat.com, nikunj.dadhania@amd.com
Cc: thomas.lendacky@amd.com, tglx@linutronix.de, mingo@redhat.com,
 bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
 michael.roth@amd.com, pankaj.gupta@amd.com, kvm@vger.kernel.org,
 linux-kernel@vger.kernel.org, santosh.shukla@amd.com
References: <20240531044644.768-4-ravi.bangoria@amd.com>
 <20240605114810.1304-1-ravi.bangoria@amd.com>
From: "Aithal, Srikanth" <sraithal@amd.com>
In-Reply-To: <20240605114810.1304-1-ravi.bangoria@amd.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?utf-8?B?TWgwOEhDWHNyNTA3N3ppd3ZjN0dqT2poTytBTVc0VTQ0NXJYK0JXMFJFOU5E?=
 =?utf-8?B?YUkwL0xOSXlaTVpRZGJtaHNTRWhKZ0crWHlqYjdjaVFmK2pzNzMxa296bkp4?=
 =?utf-8?B?MmlxbnFYdHNMYkpoeStDcDBQTDBWcUcvOHRWbHVTYmEyaEtnSVdJbGJ4SitE?=
 =?utf-8?B?djhOUklpUEM0eHA1SnYxTnRLNXFFYWhCdmJPQlY4aWhNSThxZ3JJcFhnY0VG?=
 =?utf-8?B?amRDY083Tlk1enlCcUVHRkdYbHE3Z1d0VXFTcVhoaC9SdUxpclRPKzgzUkRQ?=
 =?utf-8?B?b01qRXpBZUpnbDNPcGpXQU9jbzJNdkR0Rmtza0hEc3V3ejBTWmdZZHhTZmdX?=
 =?utf-8?B?WVdPN2tmZjhJM2xuMmdQZ1ZJRWJzdmdWeUFDOCs0NGloWWlrSmV5cGdocEsv?=
 =?utf-8?B?SXJqbEJsWXFROVVXMkxSbzhacWl2UVZ1U01YbXlwZW9KRXhKZE1JcERwMFlL?=
 =?utf-8?B?M2M5WkRua3lyNFVvNDhFT1NBUFVJLzhSWnBwcFhSTnZRZ1Viajd2RFJTcklO?=
 =?utf-8?B?QWQ2eTN2S3BRMGxVN21aUG5MVzczUDUydjEzVjg2OHdOVjkxYkxxR2ZrK2pC?=
 =?utf-8?B?SlluLy85eG1pN2tUZTBpTS80VlhJK0dvamluNVllOURXYStMRk9BcFJuR1lo?=
 =?utf-8?B?dVU2b3pFNnZpbGQ5RzFtVjBiOVppNGlndW5qeUZDS3pEOG9qNXo3TGQ5U1F6?=
 =?utf-8?B?VVdKKzFnQ0Fibk84ekJKbzJzdGpaT0t0ZlREbGVUYm5uNW90SUt3UHNZY3JJ?=
 =?utf-8?B?enFuakwrTlVhbU4vc1FlblMwdWYrUSt1MGRzRk44K2NqMktGVWloMU1NRzdp?=
 =?utf-8?B?SHpOR3dwTDBLZ29Xekt3US9ubWFiMHhKQnE1SzBUSFM5eDNTTkkwb2FUNUxp?=
 =?utf-8?B?TWdDV0V6ZXB0NHNZN1NyeTFxUWpSTEZndFk3ZGRwUTFOeWhXUndSODBvcGY1?=
 =?utf-8?B?OGpYRHB5QVBLbDlqYW55M0xrdnY2SWt5dU9ITU8xcXFMQ21OQTd5d1l6eVVh?=
 =?utf-8?B?eU5mSTJLSmF2NDRaMnFHbXdLcTBEaXVaT2NyQis1bU9SZWNDejFiUDRjZzds?=
 =?utf-8?B?NVE2U01wQkNvaVNTMTNyWDc4MEJFYURmZW9RMU9hUENvRHNkTmtCY3ltbzJt?=
 =?utf-8?B?bFIrSkRtRWRkbzV6UCtkT1pRNkF4UklQSjYyclptamxOOTVod3lqY3RiOG1p?=
 =?utf-8?B?YVZaMTFDYlloV1NYb29rUEJjWnBHZ3NTZjBrWDE0QWNWNjc1aXFIQmYrSWpO?=
 =?utf-8?B?aFZuK2U2WU9LSlJuTjNJT0VIY1VYbk01bWZMTTJLYTd6RmsvMG9TQi92MTlV?=
 =?utf-8?B?ZlYwSjVJeWMreEx5N0NCRVBzQ1FQSVRFTTkyRHMvaWxXKzY0VUo4RVVPWDZY?=
 =?utf-8?B?bEtqN0EweXF4OGFGZ0srWC9Ra2lTU1V0ZFJMaHNLSU5nUW4zR3J1VnhYWXJQ?=
 =?utf-8?B?WERCa0gxOWJNZGJld2U3QmZwYVNtdnpPK05YL3Q3VjRUcTVTWGs5aTJ4aisx?=
 =?utf-8?B?aXBPMENVR2xyZTUvKzQ3dWIybUxMOVEzeXBBNW9aMW01UmU1ZTVCQTdOSFNQ?=
 =?utf-8?B?Y2NGYWFLa24vbXF5a3A2bWJYdEZFUjg3aTJIQjlMZ0YrdTBPM1dlZGszZWcz?=
 =?utf-8?B?YU5PcVNpZURsNEdUQkV2d0ZJOXV1SFMzQTNHcXFGVlVzV08ybXFRZGNYWk9L?=
 =?utf-8?B?TnpDbjhRTnAvNHN2UUdZb0hvTHRpVkpqVnJ5TkYvRVowQXhLYmw2djJESEky?=
 =?utf-8?B?RjNWOUllQjFKZUI2c0x4WWF6UjNaYkpkNjJrc1QxYXY5M1ZJMG9aRDJIRjVt?=
 =?utf-8?B?cENRaVNidEpzT2R5UUxSeU1RN0k2WUl6WXlLRDdsZG9QUkkvNE80YllNNXM0?=
 =?utf-8?B?M2YzSmZaQmY3Q3c4bTdHMjhHaVlCeEVXVmRyQlZFUGFxT3hPMjZkV3AvNWVW?=
 =?utf-8?B?Z2tqL3RmeGs2WWtrZGFtWmZneldlcElMdldDcWIzTEUwNHE2UlBuSWZza2Ju?=
 =?utf-8?B?TDJRYmNBNDQzRnFDR0wwM3puVWl0eGJSMnM4b05IWVZvMGgzQmUrQ2d6TTRG?=
 =?utf-8?B?ZlVWaElCeDQyK0pxTTlFZzU3VGhzRlozR29GYVlsWUNxaE9HNVBCdlBabW4r?=
 =?utf-8?Q?M0XPS446+K7mSQWc+TGol2RG9?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a9caf9a4-6d0a-4b65-06ac-08dc85560f7b
X-MS-Exchange-CrossTenant-AuthSource: IA1PR12MB6460.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Jun 2024 11:53:05.6245
 (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: qydye2ADMlk9kQEZT/TKdsYbp+JGe2WQ6ou2DWRR7C9UOnsAKDPXYfXW3EXDgnk16dtHp5B2hyKtv+HakrBPsA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7795


On 6/5/2024 5:18 PM, Ravi Bangoria wrote:
> SEV-ES and thus SNP guest mandates LBR Virtualization to be _always_ ON.
> Although commit b7e4be0a224f ("KVM: SEV-ES: Delegate LBR virtualization
> to the processor") did the correct change for SEV-ES guests, it missed
> the SNP. Fix it.
>
> Reported-by: Srikanth Aithal <sraithal@amd.com>
> Fixes: b7e4be0a224f ("KVM: SEV-ES: Delegate LBR virtualization to the processor")
> Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
> ---
> - SNP support was not present while I prepared the original patches and
>    that lead to this confusion. Sorry about that.
>
>   arch/x86/kvm/svm/sev.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 7d401f8a3001..57291525e084 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2395,6 +2395,14 @@ static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
>   		}
>   
>   		svm->vcpu.arch.guest_state_protected = true;
> +		/*
> +		 * SEV-ES (and thus SNP) guest mandates LBR Virtualization to
> +		 * be _always_ ON. Enable it only after setting
> +		 * guest_state_protected because KVM_SET_MSRS allows dynamic
> +		 * toggling of LBRV (for performance reason) on write access to
> +		 * MSR_IA32_DEBUGCTLMSR when guest_state_protected is not set.
> +		 */
> +		svm_enable_lbrv(vcpu);
>   	}
>   
>   	return 0;
Tested-by: Srikanth Aithal <sraithal@amd.com>