On Mon, Jan 11, 2021, Vitaly Kuznetsov wrote: > Tom Lendacky <thomas.lendacky@xxxxxxx> writes: > > > On 1/11/21 4:42 AM, Vitaly Kuznetsov wrote: > >> Sean Christopherson <seanjc@xxxxxxxxxx> writes: > >> > >>> Unconditionally invoke sev_hardware_setup() when configuring SVM and > >>> handle clearing the module params/variable 'sev' and 'sev_es' in > >>> sev_hardware_setup(). This allows making said variables static within > >>> sev.c and reduces the odds of a collision with guest code, e.g. the guest > >>> side of things has already laid claim to 'sev_enabled'. > >>> > >>> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > >>> --- > >>> arch/x86/kvm/svm/sev.c | 11 +++++++++++ > >>> arch/x86/kvm/svm/svm.c | 15 +-------------- > >>> arch/x86/kvm/svm/svm.h | 2 -- > >>> 3 files changed, 12 insertions(+), 16 deletions(-) > >>> > >>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > >>> index 0eeb6e1b803d..8ba93b8fa435 100644 > >>> --- a/arch/x86/kvm/svm/sev.c > >>> +++ b/arch/x86/kvm/svm/sev.c > >>> @@ -27,6 +27,14 @@ > >>> > >>> #define __ex(x) __kvm_handle_fault_on_reboot(x) > >>> > >>> +/* enable/disable SEV support */ > >>> +static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT); > >>> +module_param(sev, int, 0444); > >>> + > >>> +/* enable/disable SEV-ES support */ > >>> +static int sev_es = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT); > >>> +module_param(sev_es, int, 0444); > >> > >> Two stupid questions (and not really related to your patch) for > >> self-eduacation if I may: > >> > >> 1) Why do we rely on CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT (which > >> sound like it control the guest side of things) to set defaults here? > > > > I thought it was a review comment, but I'm not able to find it now. > > > > Brijesh probably remembers better than me. > > > >> > >> 2) It appears to be possible to do 'modprobe kvm_amd sev=0 sev_es=1' and > >> this looks like a bogus configuration, should we make an effort to > >> validate the correctness upon module load? > > > > This will still result in an overall sev=0 sev_es=0. Is the question just > > about issuing a message based on the initial values specified? > > > > Yes, as one may expect the result will be that SEV-ES guests work and > plain SEV don't. KVM doesn't issue messages when it overrides other module params due to disable requirements, e.g. ept=0 unrestricted_guest=1 is roughly equivalent. Not that what KVM currently does is right, but at least it's consistent. :-) And on the other hand, I think it's reasonable to expect that specifying only sev=0 is sufficient to disable both SEV and SEV-ES, e.g. to turn them off when they're enabled by default.
