From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brijesh Singh Subject: Re: [PATCH v5 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active Date: Thu, 6 Sep 2018 13:37:50 -0500 Message-ID: References: <1536234182-2809-1-git-send-email-brijesh.singh@amd.com> <1536234182-2809-6-git-send-email-brijesh.singh@amd.com> <20180906122423.GA11144@zn.tnic> <20180906135041.GB32336@linux.intel.com> <20180906141825.GB370@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: brijesh.singh@amd.com, x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Tom Lendacky , Thomas Gleixner , "H. Peter Anvin" , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= To: Sean Christopherson , Borislav Petkov Return-path: In-Reply-To: <20180906141825.GB370@linux.intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 09/06/2018 09:18 AM, Sean Christopherson wrote: .... >>> >>> So are we going to be defining a decrypted section for every piece of >>> machinery now? >>> >>> That's a bit too much in my book. >>> >>> Why can't you simply free everything in .data..decrypted on !SVE guests? >> >> That would prevent adding __decrypted to existing declarations, e.g. >> hv_clock_boot, which would be ugly in its own right. A more generic >> solution would be to add something like __decrypted_exclusive to mark >> data that is used if and only if SEV is active, and then free the >> SEV-only data when SEV is disabled. > > Oh, and we'd need to make sure __decrypted_exclusive is freed when > !CONFIG_AMD_MEM_ENCRYPT, and preferably !sev_active() since the big > array is used only if SEV is active. This patch unconditionally > defines hv_clock_dec but only frees it if CONFIG_AMD_MEM_ENCRYPT=y && > !mem_encrypt_active(). > Again we have to consider the bare metal scenario while doing this. The aux array you proposed will be added in decrypted section only when CONFIG_AMD_MEM_ENCRYPT=y. If CONFIG_AMD_MEM_ENCRYPT=n then nothng gets put in .data.decrypted section. At the runtime, if memory encryption is active then .data.decrypted_hvclock will contains useful data. The __decrypted attribute in "" when CONFIG_AMD_MEM_ENCRYPT=n. -Brijesh