On Thu, Sep 06, 2018 at 02:24:32PM -0500, Brijesh Singh wrote: > > > On 09/06/2018 01:47 PM, Sean Christopherson wrote: > >On Thu, Sep 06, 2018 at 01:37:50PM -0500, Brijesh Singh wrote: > >> > >> > >>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. > > > >Right, but won't the data get dumped into the regular .bss in that > >case, i.e. needs to be freed? > > > > > Yes, the auxiliary array will dumped into the regular .bss when > CONFIG_AMD_MEM_ENCRYPT=n. Typically it will be few k, I am not > sure if its worth complicating the code to save those extra memory. > Most of the distro's have CONFIG_AMD_MEM_ENCRYPT=y anyways. I just realized that we'll try to create a bogus array if 'NR_CPUS <= HVC_BOOT_ARRAY_SIZE'. A bit ugly, but we could #ifdef away both that and CONFIG_AMD_MEM_ENCRYPT=n in a single shot, e.g.: #if defined(CONFIG_AMD_MEM_ENCRYPT) && NR_CPUS > HVC_BOOT_ARRAY_SIZE #define HVC_AUX_ARRAY_SIZE \ PAGE_ALIGN((NR_CPUS - HVC_BOOT_ARRAY_SIZE) * \ sizeof(struct pvclock_vsyscall_time_info)) static struct pvclock_vsyscall_time_info hv_clock_aux[HVC_AUX_ARRAY_SIZE] __decrypted __aligned(PAGE_SIZE); #endif
