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The new Asynchronous Exit (AEX) notification mechanism (AEX-notify) allows one enclave to receive a notification in the ERESUME after the enclave exit due to an AEX. EDECCSSA is a new SGX user leaf function (ENCLU[EDECCSSA]) to facilitate the AEX notification handling. The new EDECCSSA is enumerated via CPUID(EAX=0x12,ECX=0x0):EAX[11]. Besides Allowing reporting the new AEX-notify attribute to KVM guests, also allow reporting the new EDECCSSA user leaf function to KVM guests so the guest can fully utilize the AEX-notify mechanism. Similar to existing X86_FEATURE_SGX1 and X86_FEATURE_SGX2, introduce a new scattered X86_FEATURE_SGX_EDECCSSA bit for the new EDECCSSA, and report it in KVM's supported CPUIDs. Note, no additional KVM enabling is required to allow the guest to use EDECCSSA. It's impossible to trap ENCLU (without completely preventing the guest from using SGX). Advertise EDECCSSA as supported purely so that userspace doesn't need to special case EDECCSSA, i.e. doesn't need to manually check host CPUID. The inability to trap ENCLU also means that KVM can't prevent the guest from using EDECCSSA, but that virtualization hole is benign as far as KVM is concerned. EDECCSSA is simply a fancy way to modify internal enclave state. More background about how do AEX-notify and EDECCSSA work: SGX maintains a Current State Save Area Frame (CSSA) for each enclave thread. When AEX happens, the enclave thread context is saved to the CSSA and the CSSA is increased by 1. For a normal ERESUME which doesn't deliver AEX notification, it restores the saved thread context from the previously saved SSA and decreases the CSSA. If AEX-notify is enabled for one enclave, the ERESUME acts differently. Instead of restoring the saved thread context and decreasing the CSSA, it acts like EENTER which doesn't decrease the CSSA but establishes a clean slate thread context using the CSSA for the enclave to handle the notification. After some handling, the enclave must discard the "new-established" SSA and switch back to the previously saved SSA (upon AEX). Otherwise, the enclave will run out of SSA space upon further AEXs and eventually fail to run. To solve this problem, the new EDECCSSA essentially decreases the CSSA. It can be used by the enclave notification handler to switch back to the previous saved SSA when needed, i.e. after it handles the notification. Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Sean Christopherson <seanjc@google.com> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lore.kernel.org/all/20221101022422.858944-1-kai.huang%40intel.com
141 lines
5 KiB
C
141 lines
5 KiB
C
/* Declare dependencies between CPUIDs */
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <asm/cpufeature.h>
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struct cpuid_dep {
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unsigned int feature;
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unsigned int depends;
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};
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/*
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* Table of CPUID features that depend on others.
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*
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* This only includes dependencies that can be usefully disabled, not
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* features part of the base set (like FPU).
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*
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* Note this all is not __init / __initdata because it can be
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* called from cpu hotplug. It shouldn't do anything in this case,
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* but it's difficult to tell that to the init reference checker.
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*/
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static const struct cpuid_dep cpuid_deps[] = {
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{ X86_FEATURE_FXSR, X86_FEATURE_FPU },
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{ X86_FEATURE_XSAVEOPT, X86_FEATURE_XSAVE },
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{ X86_FEATURE_XSAVEC, X86_FEATURE_XSAVE },
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{ X86_FEATURE_XSAVES, X86_FEATURE_XSAVE },
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{ X86_FEATURE_AVX, X86_FEATURE_XSAVE },
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{ X86_FEATURE_PKU, X86_FEATURE_XSAVE },
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{ X86_FEATURE_MPX, X86_FEATURE_XSAVE },
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{ X86_FEATURE_XGETBV1, X86_FEATURE_XSAVE },
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{ X86_FEATURE_CMOV, X86_FEATURE_FXSR },
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{ X86_FEATURE_MMX, X86_FEATURE_FXSR },
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{ X86_FEATURE_MMXEXT, X86_FEATURE_MMX },
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{ X86_FEATURE_FXSR_OPT, X86_FEATURE_FXSR },
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{ X86_FEATURE_XSAVE, X86_FEATURE_FXSR },
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{ X86_FEATURE_XMM, X86_FEATURE_FXSR },
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{ X86_FEATURE_XMM2, X86_FEATURE_XMM },
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{ X86_FEATURE_XMM3, X86_FEATURE_XMM2 },
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{ X86_FEATURE_XMM4_1, X86_FEATURE_XMM2 },
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{ X86_FEATURE_XMM4_2, X86_FEATURE_XMM2 },
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{ X86_FEATURE_XMM3, X86_FEATURE_XMM2 },
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{ X86_FEATURE_PCLMULQDQ, X86_FEATURE_XMM2 },
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{ X86_FEATURE_SSSE3, X86_FEATURE_XMM2, },
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{ X86_FEATURE_F16C, X86_FEATURE_XMM2, },
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{ X86_FEATURE_AES, X86_FEATURE_XMM2 },
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{ X86_FEATURE_SHA_NI, X86_FEATURE_XMM2 },
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{ X86_FEATURE_FMA, X86_FEATURE_AVX },
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{ X86_FEATURE_AVX2, X86_FEATURE_AVX, },
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{ X86_FEATURE_AVX512F, X86_FEATURE_AVX, },
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{ X86_FEATURE_AVX512IFMA, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512PF, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512ER, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512CD, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512DQ, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512BW, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512VL, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512VBMI, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512_VBMI2, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_GFNI, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_VAES, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_VPCLMULQDQ, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_AVX512_VNNI, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_AVX512_BITALG, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_AVX512_4VNNIW, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512_4FMAPS, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512_VPOPCNTDQ, X86_FEATURE_AVX512F },
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{ X86_FEATURE_AVX512_VP2INTERSECT, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_CQM_OCCUP_LLC, X86_FEATURE_CQM_LLC },
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{ X86_FEATURE_CQM_MBM_TOTAL, X86_FEATURE_CQM_LLC },
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{ X86_FEATURE_CQM_MBM_LOCAL, X86_FEATURE_CQM_LLC },
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{ X86_FEATURE_AVX512_BF16, X86_FEATURE_AVX512VL },
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{ X86_FEATURE_AVX512_FP16, X86_FEATURE_AVX512BW },
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{ X86_FEATURE_ENQCMD, X86_FEATURE_XSAVES },
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{ X86_FEATURE_PER_THREAD_MBA, X86_FEATURE_MBA },
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{ X86_FEATURE_SGX_LC, X86_FEATURE_SGX },
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{ X86_FEATURE_SGX1, X86_FEATURE_SGX },
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{ X86_FEATURE_SGX2, X86_FEATURE_SGX1 },
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{ X86_FEATURE_SGX_EDECCSSA, X86_FEATURE_SGX1 },
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{ X86_FEATURE_XFD, X86_FEATURE_XSAVES },
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{ X86_FEATURE_XFD, X86_FEATURE_XGETBV1 },
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{ X86_FEATURE_AMX_TILE, X86_FEATURE_XFD },
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{}
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};
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static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
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{
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/*
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* Note: This could use the non atomic __*_bit() variants, but the
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* rest of the cpufeature code uses atomics as well, so keep it for
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* consistency. Cleanup all of it separately.
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*/
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if (!c) {
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clear_cpu_cap(&boot_cpu_data, feature);
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set_bit(feature, (unsigned long *)cpu_caps_cleared);
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} else {
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clear_bit(feature, (unsigned long *)c->x86_capability);
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}
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}
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/* Take the capabilities and the BUG bits into account */
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#define MAX_FEATURE_BITS ((NCAPINTS + NBUGINTS) * sizeof(u32) * 8)
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static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
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{
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DECLARE_BITMAP(disable, MAX_FEATURE_BITS);
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const struct cpuid_dep *d;
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bool changed;
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if (WARN_ON(feature >= MAX_FEATURE_BITS))
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return;
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clear_feature(c, feature);
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/* Collect all features to disable, handling dependencies */
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memset(disable, 0, sizeof(disable));
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__set_bit(feature, disable);
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/* Loop until we get a stable state. */
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do {
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changed = false;
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for (d = cpuid_deps; d->feature; d++) {
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if (!test_bit(d->depends, disable))
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continue;
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if (__test_and_set_bit(d->feature, disable))
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continue;
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changed = true;
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clear_feature(c, d->feature);
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}
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} while (changed);
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}
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void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
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{
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do_clear_cpu_cap(c, feature);
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}
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void setup_clear_cpu_cap(unsigned int feature)
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{
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do_clear_cpu_cap(NULL, feature);
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}
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