linux-stable/arch/x86/kernel/cpu/feat_ctl.c
Sean Christopherson 332bfc7bec x86/cpu/intel: Allow SGX virtualization without Launch Control support
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>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Link: https://lkml.kernel.org/r/b3329777076509b3b601550da288c8f3c406a865.1616136308.git.kai.huang@intel.com
2021-04-06 09:43:41 +02:00

205 lines
6.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/tboot.h>
#include <asm/cpufeature.h>
#include <asm/msr-index.h>
#include <asm/processor.h>
#include <asm/vmx.h>
#include "cpu.h"
#undef pr_fmt
#define pr_fmt(fmt) "x86/cpu: " fmt
#ifdef CONFIG_X86_VMX_FEATURE_NAMES
enum vmx_feature_leafs {
MISC_FEATURES = 0,
PRIMARY_CTLS,
SECONDARY_CTLS,
NR_VMX_FEATURE_WORDS,
};
#define VMX_F(x) BIT(VMX_FEATURE_##x & 0x1f)
static void init_vmx_capabilities(struct cpuinfo_x86 *c)
{
u32 supported, funcs, ept, vpid, ign;
BUILD_BUG_ON(NVMXINTS != NR_VMX_FEATURE_WORDS);
/*
* The high bits contain the allowed-1 settings, i.e. features that can
* be turned on. The low bits contain the allowed-0 settings, i.e.
* features that can be turned off. Ignore the allowed-0 settings,
* if a feature can be turned on then it's supported.
*
* Use raw rdmsr() for primary processor controls and pin controls MSRs
* as they exist on any CPU that supports VMX, i.e. we want the WARN if
* the RDMSR faults.
*/
rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, ign, supported);
c->vmx_capability[PRIMARY_CTLS] = supported;
rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS2, &ign, &supported);
c->vmx_capability[SECONDARY_CTLS] = supported;
rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
rdmsr_safe(MSR_IA32_VMX_VMFUNC, &ign, &funcs);
/*
* Except for EPT+VPID, which enumerates support for both in a single
* MSR, low for EPT, high for VPID.
*/
rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, &ept, &vpid);
/* Pin, EPT, VPID and VM-Func are merged into a single word. */
WARN_ON_ONCE(supported >> 16);
WARN_ON_ONCE(funcs >> 4);
c->vmx_capability[MISC_FEATURES] = (supported & 0xffff) |
((vpid & 0x1) << 16) |
((funcs & 0xf) << 28);
/* EPT bits are full on scattered and must be manually handled. */
if (ept & VMX_EPT_EXECUTE_ONLY_BIT)
c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_EXECUTE_ONLY);
if (ept & VMX_EPT_AD_BIT)
c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_AD);
if (ept & VMX_EPT_1GB_PAGE_BIT)
c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_1GB);
/* Synthetic APIC features that are aggregates of multiple features. */
if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
(c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_APIC_ACCESSES)))
c->vmx_capability[MISC_FEATURES] |= VMX_F(FLEXPRIORITY);
if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) &&
(c->vmx_capability[SECONDARY_CTLS] & VMX_F(APIC_REGISTER_VIRT)) &&
(c->vmx_capability[SECONDARY_CTLS] & VMX_F(VIRT_INTR_DELIVERY)) &&
(c->vmx_capability[MISC_FEATURES] & VMX_F(POSTED_INTR)))
c->vmx_capability[MISC_FEATURES] |= VMX_F(APICV);
/* Set the synthetic cpufeatures to preserve /proc/cpuinfo's ABI. */
if (c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR))
set_cpu_cap(c, X86_FEATURE_TPR_SHADOW);
if (c->vmx_capability[MISC_FEATURES] & VMX_F(FLEXPRIORITY))
set_cpu_cap(c, X86_FEATURE_FLEXPRIORITY);
if (c->vmx_capability[MISC_FEATURES] & VMX_F(VIRTUAL_NMIS))
set_cpu_cap(c, X86_FEATURE_VNMI);
if (c->vmx_capability[SECONDARY_CTLS] & VMX_F(EPT))
set_cpu_cap(c, X86_FEATURE_EPT);
if (c->vmx_capability[MISC_FEATURES] & VMX_F(EPT_AD))
set_cpu_cap(c, X86_FEATURE_EPT_AD);
if (c->vmx_capability[MISC_FEATURES] & VMX_F(VPID))
set_cpu_cap(c, X86_FEATURE_VPID);
}
#endif /* CONFIG_X86_VMX_FEATURE_NAMES */
static int __init nosgx(char *str)
{
setup_clear_cpu_cap(X86_FEATURE_SGX);
return 0;
}
early_param("nosgx", nosgx);
void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
{
bool enable_sgx_kvm = false, enable_sgx_driver = false;
bool tboot = tboot_enabled();
bool enable_vmx;
u64 msr;
if (rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr)) {
clear_cpu_cap(c, X86_FEATURE_VMX);
clear_cpu_cap(c, X86_FEATURE_SGX);
return;
}
enable_vmx = cpu_has(c, X86_FEATURE_VMX) &&
IS_ENABLED(CONFIG_KVM_INTEL);
if (cpu_has(c, X86_FEATURE_SGX) && IS_ENABLED(CONFIG_X86_SGX)) {
/*
* 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 Launch Control is not
* available.
*/
enable_sgx_driver = cpu_has(c, X86_FEATURE_SGX_LC);
enable_sgx_kvm = enable_vmx && IS_ENABLED(CONFIG_X86_SGX_KVM);
}
if (msr & FEAT_CTL_LOCKED)
goto update_caps;
/*
* Ignore whatever value BIOS left in the MSR to avoid enabling random
* features or faulting on the WRMSR.
*/
msr = FEAT_CTL_LOCKED;
/*
* Enable VMX if and only if the kernel may do VMXON at some point,
* i.e. KVM is enabled, to avoid unnecessarily adding an attack vector
* for the kernel, e.g. using VMX to hide malicious code.
*/
if (enable_vmx) {
msr |= FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
if (tboot)
msr |= FEAT_CTL_VMX_ENABLED_INSIDE_SMX;
}
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);
update_caps:
set_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
if (!cpu_has(c, X86_FEATURE_VMX))
goto update_sgx;
if ( (tboot && !(msr & FEAT_CTL_VMX_ENABLED_INSIDE_SMX)) ||
(!tboot && !(msr & FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX))) {
if (IS_ENABLED(CONFIG_KVM_INTEL))
pr_err_once("VMX (%s TXT) disabled by BIOS\n",
tboot ? "inside" : "outside");
clear_cpu_cap(c, X86_FEATURE_VMX);
} else {
#ifdef CONFIG_X86_VMX_FEATURE_NAMES
init_vmx_capabilities(c);
#endif
}
update_sgx:
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);
}
}
}