On Fri, 5 Mar 2021 18:29:57 +0100 Borislav Petkov wrote:
> On Mon, Mar 01, 2021 at 10:45:02PM +1300, Kai Huang wrote:
> > From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> >
> > The kernel will currently disable all SGX support if the hardware does
> > not support launch control. Make it more permissive to allow SGX
> > virtualization on systems without Launch Control support. This will
> > allow KVM to expose SGX to guests that have less-strict requirements on
> > the availability of flexible launch control.
> >
> > Improve error message to distinguish between three cases. There are two
> > cases where SGX support is completely disabled:
> > 1) SGX has been disabled completely by the BIOS
> > 2) SGX LC is locked by the BIOS. Bare-metal support is disabled because
> > of LC unavailability. SGX virtualization is unavailable (because of
> > Kconfig).
> > One where it is partially available:
> > 3) SGX LC is locked by the BIOS. Bare-metal support is disabled because
> > of LC unavailability. SGX virtualization is supported.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Co-developed-by: Kai Huang <kai.huang@xxxxxxxxx>
> > Acked-by: Dave Hansen <dave.hansen@xxxxxxxxx>
> > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> > ---
> > arch/x86/kernel/cpu/feat_ctl.c | 57 ++++++++++++++++++++++++++--------
> > 1 file changed, 44 insertions(+), 13 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
> > index 27533a6e04fa..96c370284913 100644
> > --- a/arch/x86/kernel/cpu/feat_ctl.c
> > +++ b/arch/x86/kernel/cpu/feat_ctl.c
> > @@ -105,7 +105,8 @@ early_param("nosgx", nosgx);
> > void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
> > {
> > bool tboot = tboot_enabled();
> > - bool enable_sgx;
> > + bool enable_sgx_any, enable_sgx_kvm, enable_sgx_driver;
> > + bool enable_vmx;
> > u64 msr;
>
> The preferred ordering of variable declarations at the beginning of a
> function is reverse fir tree order::
>
> struct long_struct_name *descriptive_name;
> unsigned long foo, bar;
> unsigned int tmp;
> int ret;
>
Will do.
Since as you suggested, enable_sgx_any will be removed, and initializing
enable_sgx_driver/kvm will be moved into the if () statement, I think we should
explicitly initialize them here. How about below?
bool enable_sgx_kvm = enable_sgx_driver = false;
bool tboot = tboot_enabled();
bool enable_vmx;
...
>
> > if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
> > @@ -114,13 +115,21 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
> > return;
> > }
> >
> > + enable_vmx = cpu_has(c, X86_FEATURE_VMX) &&
> > + IS_ENABLED(CONFIG_KVM_INTEL);
> > +
> > /*
> > - * Enable SGX if and only if the kernel supports SGX and Launch Control
> > - * is supported, i.e. disable SGX if the LE hash MSRs can't be written.
> > + * Separate out SGX driver enabling from KVM. This allows KVM
> > + * guests to use SGX even if the kernel SGX driver refuses to
> > + * use it. This happens if flexible Faunch Control is not
> > + * available.
> > */
> > - enable_sgx = cpu_has(c, X86_FEATURE_SGX) &&
> > - cpu_has(c, X86_FEATURE_SGX_LC) &&
> > - IS_ENABLED(CONFIG_X86_SGX);
> > + enable_sgx_any = cpu_has(c, X86_FEATURE_SGX) &&
> > + IS_ENABLED(CONFIG_X86_SGX);
> > + enable_sgx_driver = enable_sgx_any &&
> > + cpu_has(c, X86_FEATURE_SGX_LC);
> > + enable_sgx_kvm = enable_sgx_any && enable_vmx &&
> > + IS_ENABLED(CONFIG_X86_SGX_KVM);
>
> That enable_sgx_any use looks weird. You can get rid of it:
>
> if (cpu_has(c, X86_FEATURE_SGX) && IS_ENABLED(CONFIG_X86_SGX)) {
> enable_sgx_driver = cpu_has(c, X86_FEATURE_SGX_LC);
> enable_sgx_kvm = enable_vmx && IS_ENABLED(CONFIG_X86_SGX_KVM);
> }
>
> and yap, let longer lines stick out.
Thanks. Will do.
>
> Thx.
>
> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette
