diff mbox series

[06/25] x86/cpu/intel: Allow SGX virtualization without Launch Control support

Message ID 12541888ae9ac7f517582aa64d9153feede7aed4.1614590788.git.kai.huang@intel.com (mailing list archive)
State New, archived
Headers show
Series KVM SGX virtualization support | expand

Commit Message

Huang, Kai March 1, 2021, 9:45 a.m. UTC 
From: Sean Christopherson <sean.j.christopherson@intel.com>

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@intel.com>
Co-developed-by: Kai Huang <kai.huang@intel.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/kernel/cpu/feat_ctl.c | 57 ++++++++++++++++++++++++++--------
 1 file changed, 44 insertions(+), 13 deletions(-)

Comments

Borislav Petkov March 5, 2021, 5:29 p.m. UTC | #1 
On Mon, Mar 01, 2021 at 10:45:02PM +1300, Kai Huang wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
> 
> 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@intel.com>
> Co-developed-by: Kai Huang <kai.huang@intel.com>
> Acked-by: Dave Hansen <dave.hansen@intel.com>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> ---
>  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;


>  	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.

Thx.
Huang, Kai March 7, 2021, 11:50 p.m. UTC | #2 
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@intel.com>
> > 
> > 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@intel.com>
> > Co-developed-by: Kai Huang <kai.huang@intel.com>
> > Acked-by: Dave Hansen <dave.hansen@intel.com>
> > Signed-off-by: Kai Huang <kai.huang@intel.com>
> > ---
> >  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
Huang, Kai March 8, 2021, 12:19 a.m. UTC | #3 
On Mon, 8 Mar 2021 12:50:26 +1300 Kai Huang wrote:
> 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@intel.com>
> > > 
> > > 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@intel.com>
> > > Co-developed-by: Kai Huang <kai.huang@intel.com>
> > > Acked-by: Dave Hansen <dave.hansen@intel.com>
> > > Signed-off-by: Kai Huang <kai.huang@intel.com>
> > > ---
> > >  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;

Sorry my bad, should be:

	bool enable_sgx_kvm = false, 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
Jarkko Sakkinen March 10, 2021, 3:32 p.m. UTC | #4 
On Fri, Mar 05, 2021 at 06:29:57PM +0100, Borislav Petkov wrote:
> On Mon, Mar 01, 2021 at 10:45:02PM +1300, Kai Huang wrote:
> > From: Sean Christopherson <sean.j.christopherson@intel.com>
> > 
> > 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@intel.com>
> > Co-developed-by: Kai Huang <kai.huang@intel.com>
> > Acked-by: Dave Hansen <dave.hansen@intel.com>
> > Signed-off-by: Kai Huang <kai.huang@intel.com>
> > ---
> >  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;

IMHO here declaring separate lines would make also sense, given
how long the local variable names are.

 /Jarkko
diff mbox series

Patch

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;
 
 	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);
 
 	if (msr & FEAT_CTL_LOCKED)
 		goto update_caps;
@@ -136,15 +145,18 @@  void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 	 * i.e. KVM is enabled, to avoid unnecessarily adding an attack vector
 	 * for the kernel, e.g. using VMX to hide malicious code.
 	 */
-	if (cpu_has(c, X86_FEATURE_VMX) && IS_ENABLED(CONFIG_KVM_INTEL)) {
+	if (enable_vmx) {
 		msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
 
 		if (tboot)
 			msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
 	}
 
-	if (enable_sgx)
-		msr |= FEAT_CTL_SGX_ENABLED | FEAT_CTL_SGX_LC_ENABLED;
+	if (enable_sgx_kvm || enable_sgx_driver) {
+		msr |= FEAT_CTL_SGX_ENABLED;
+		if (enable_sgx_driver)
+			msr |= FEAT_CTL_SGX_LC_ENABLED;
+	}
 
 	wrmsrl(MSR_IA32_FEAT_CTL, msr);
 
@@ -167,10 +179,29 @@  void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 	}
 
 update_sgx:
-	if (!(msr & FEAT_CTL_SGX_ENABLED) ||
-	    !(msr & FEAT_CTL_SGX_LC_ENABLED) || !enable_sgx) {
-		if (enable_sgx)
-			pr_err_once("SGX disabled by BIOS\n");
+	if (!(msr & FEAT_CTL_SGX_ENABLED)) {
+		if (enable_sgx_kvm || enable_sgx_driver)
+			pr_err_once("SGX disabled by BIOS.\n");
 		clear_cpu_cap(c, X86_FEATURE_SGX);
+		return;
+	}
+
+	/*
+	 * VMX feature bit may be cleared due to being disabled in BIOS,
+	 * in which case SGX virtualization cannot be supported either.
+	 */
+	if (!cpu_has(c, X86_FEATURE_VMX) && enable_sgx_kvm) {
+		pr_err_once("SGX virtualization disabled due to lack of VMX.\n");
+		enable_sgx_kvm = 0;
+	}
+
+	if (!(msr & FEAT_CTL_SGX_LC_ENABLED) && enable_sgx_driver) {
+		if (!enable_sgx_kvm) {
+			pr_err_once("SGX Launch Control is locked. Disable SGX.\n");
+			clear_cpu_cap(c, X86_FEATURE_SGX);
+		} else {
+			pr_err_once("SGX Launch Control is locked. Support SGX virtualization only.\n");
+			clear_cpu_cap(c, X86_FEATURE_SGX_LC);
+		}
 	}
 }