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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id y8sm2812916wmi.45.2021.06.08.09.22.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Jun 2021 09:22:16 -0700 (PDT) Subject: Re: [PATCH] KVM: SVM: Fix SEV SEND_START session length & SEND_UPDATE_DATA query length after commit 238eca821cee To: Ashish Kalra Cc: seanjc@google.com, tglx@linutronix.de, bp@alien8.de, mingo@redhat.com, hpa@zytor.com, joro@8bytes.org, Thomas.Lendacky@amd.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, srutherford@google.com, brijesh.singh@amd.com References: <20210607061532.27459-1-Ashish.Kalra@amd.com> From: Paolo Bonzini Message-ID: Date: Tue, 8 Jun 2021 18:22:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210607061532.27459-1-Ashish.Kalra@amd.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/06/21 08:15, Ashish Kalra wrote: > From: Ashish Kalra > > Commit 238eca821cee ("KVM: SVM: Allocate SEV command structures on local stack") > uses the local stack to allocate the structures used to communicate with the PSP, > which were earlier being kzalloced. This breaks SEV live migration for > computing the SEND_START session length and SEND_UPDATE_DATA query length as > session_len and trans_len and hdr_len fields are not zeroed respectively for > the above commands before issuing the SEV Firmware API call, hence the > firmware returns incorrect session length and update data header or trans length. > > Also the SEV Firmware API returns SEV_RET_INVALID_LEN firmware error > for these length query API calls, and the return value and the > firmware error needs to be passed to the userspace as it is, so > need to remove the return check in the KVM code. > > Signed-off-by: Ashish Kalra > --- > arch/x86/kvm/svm/sev.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 5bc887e9a986..e0ce5da97fc2 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -1103,10 +1103,9 @@ __sev_send_start_query_session_length(struct kvm *kvm, struct kvm_sev_cmd *argp, > struct sev_data_send_start data; > int ret; > > + memset(&data, 0, sizeof(data)); > data.handle = sev->handle; > ret = sev_issue_cmd(kvm, SEV_CMD_SEND_START, &data, &argp->error); > - if (ret < 0) > - return ret; > > params->session_len = data.session_len; > if (copy_to_user((void __user *)(uintptr_t)argp->data, params, > @@ -1215,10 +1214,9 @@ __sev_send_update_data_query_lengths(struct kvm *kvm, struct kvm_sev_cmd *argp, > struct sev_data_send_update_data data; > int ret; > > + memset(&data, 0, sizeof(data)); > data.handle = sev->handle; > ret = sev_issue_cmd(kvm, SEV_CMD_SEND_UPDATE_DATA, &data, &argp->error); > - if (ret < 0) > - return ret; > > params->hdr_len = data.hdr_len; > params->trans_len = data.trans_len; > Queued, thanks. Paolo