Add a new library to the KVM selftest framework to manage and enable Secure AVIC, providing the foundation for testing this feature.
Secure AVIC (SAVIC) is an AMD SEV-SNP feature that provides each vCPU with a guest-owned APIC backing page in memory. This allow SEV-SNP guests to prevent the hypervisor from generating unexpected interrupts to a vCPU or otherwise violate architectural assumptions around APIC behavior.
The core of the new library (lib/x86/savic.c) revolves around the management of these APIC backing pages:
- Allocate pool of APIC backing pages during the SNP VM launch sequence if the VMSA features report SAVIC support. - Update kvm_arch_vm_additional_pages_required() helper to ensure sufficient memory is pre-allocated for these pages during VM creation.
The library exposes a set of helpers for guest code:
- savic_enable(): The primary function for a vCPU to switch into Secure AVIC mode.
- savic_read/write_reg(): Allow the guest to interact with its local APIC state via the backing page once SAVIC is active.
- savic_hv_read/write_reg(): Helpers that wrap the PV MSR interface for communicating with KVM's view of the APIC state.
This infrastructure is a prerequisite for writing selftests that verify the correctness of Secure AVIC.
Signed-off-by: Neeraj Upadhyay Neeraj.Upadhyay@amd.com --- tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/include/x86/apic.h | 6 + .../testing/selftests/kvm/include/x86/savic.h | 19 ++ tools/testing/selftests/kvm/include/x86/svm.h | 3 + .../testing/selftests/kvm/lib/x86/processor.c | 7 +- tools/testing/selftests/kvm/lib/x86/savic.c | 205 ++++++++++++++++++ tools/testing/selftests/kvm/lib/x86/sev.c | 15 ++ 7 files changed, 254 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/kvm/include/x86/savic.h create mode 100644 tools/testing/selftests/kvm/lib/x86/savic.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm index 41aa99e5e0c4..b94ac1caa514 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -26,6 +26,7 @@ LIBKVM_x86 += lib/x86/insn-eval.c LIBKVM_x86 += lib/x86/memstress.c LIBKVM_x86 += lib/x86/pmu.c LIBKVM_x86 += lib/x86/processor.c +LIBKVM_x86 += lib/x86/savic.c LIBKVM_x86 += lib/x86/sev.c LIBKVM_x86 += lib/x86/svm.c LIBKVM_x86 += lib/x86/ucall.c diff --git a/tools/testing/selftests/kvm/include/x86/apic.h b/tools/testing/selftests/kvm/include/x86/apic.h index 80fe9f69b38d..6ba5d0545bf8 100644 --- a/tools/testing/selftests/kvm/include/x86/apic.h +++ b/tools/testing/selftests/kvm/include/x86/apic.h @@ -29,6 +29,7 @@ #define APIC_TASKPRI 0x80 #define APIC_PROCPRI 0xA0 #define APIC_EOI 0xB0 +#define APIC_LDR 0xD0 #define APIC_SPIV 0xF0 #define APIC_SPIV_FOCUS_DISABLED (1 << 9) #define APIC_SPIV_APIC_ENABLED (1 << 8) @@ -60,10 +61,15 @@ #define APIC_ICR2 0x310 #define SET_APIC_DEST_FIELD(x) ((x) << 24) #define APIC_LVTT 0x320 +#define APIC_LVTTHMR 0x330 +#define APIC_LVTPC 0x340 +#define APIC_LVT0 0x350 #define APIC_LVT_TIMER_ONESHOT (0 << 17) #define APIC_LVT_TIMER_PERIODIC (1 << 17) #define APIC_LVT_TIMER_TSCDEADLINE (2 << 17) #define APIC_LVT_MASKED (1 << 16) +#define APIC_LVT1 0x360 +#define APIC_LVTERR 0x370 #define APIC_TMICT 0x380 #define APIC_TMCCT 0x390 #define APIC_TDCR 0x3E0 diff --git a/tools/testing/selftests/kvm/include/x86/savic.h b/tools/testing/selftests/kvm/include/x86/savic.h new file mode 100644 index 000000000000..1ab92dad00c1 --- /dev/null +++ b/tools/testing/selftests/kvm/include/x86/savic.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Helpers used for Secure AVIC guests + * + */ +#ifndef SELFTEST_KVM_SAVIC_H +#define SELFTEST_KVM_SAVIC_H + +struct guest_apic_page; + +void guest_apic_pages_init(struct kvm_vm *vm); +void set_savic_control_msr(struct guest_apic_page *apic_page, bool enable, bool enable_nmi); +void savic_write_reg(struct guest_apic_page *apic_page, uint32_t reg, uint64_t val); +uint64_t savic_read_reg(struct guest_apic_page *apic_page, uint32_t reg); +void savic_hv_write_reg(uint32_t reg, uint64_t val); +uint64_t savic_hv_read_reg(uint32_t reg); +void savic_enable(void); +int savic_nr_pages_required(uint64_t page_size); +#endif diff --git a/tools/testing/selftests/kvm/include/x86/svm.h b/tools/testing/selftests/kvm/include/x86/svm.h index 66dd4eaf23b9..689fefb72d06 100644 --- a/tools/testing/selftests/kvm/include/x86/svm.h +++ b/tools/testing/selftests/kvm/include/x86/svm.h @@ -179,6 +179,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area { #define SVM_NESTED_CTL_NP_ENABLE BIT(0) #define SVM_NESTED_CTL_SEV_ENABLE BIT(1)
+#define SVM_FEAT_SECURE_AVIC 16 +#define SVM_FEAT_ALLOWED_SEV_FEATURES_VALID 63 + struct __attribute__ ((__packed__)) vmcb_seg { u16 selector; u16 attrib; diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c index 181f1943c4be..a33a09a161d3 100644 --- a/tools/testing/selftests/kvm/lib/x86/processor.c +++ b/tools/testing/selftests/kvm/lib/x86/processor.c @@ -659,10 +659,13 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm)
int kvm_arch_vm_additional_pages_required(struct vm_shape shape, uint64_t page_size) { - if (shape.type == KVM_X86_SEV_ES_VM || - shape.type == KVM_X86_SNP_VM) + if (shape.type == KVM_X86_SEV_ES_VM) return ghcb_nr_pages_required(page_size);
+ if (shape.type == KVM_X86_SNP_VM) + return ghcb_nr_pages_required(page_size) + + savic_nr_pages_required(page_size); + return 0; }
diff --git a/tools/testing/selftests/kvm/lib/x86/savic.c b/tools/testing/selftests/kvm/lib/x86/savic.c new file mode 100644 index 000000000000..72ad43d4797e --- /dev/null +++ b/tools/testing/selftests/kvm/lib/x86/savic.c @@ -0,0 +1,205 @@ +// SPDX-License-Identifier: GPL-2.0-only + +/* + * Copyright (C) 2024 Advanced Micro Devices, Inc. + * + */ + +#include "apic.h" +#include "kvm_util.h" +#include "sev.h" + +struct apic_page { + u8 apic_regs[PAGE_SIZE]; +} __packed; + +struct guest_apic_page { + struct apic_page apic_page; + uint64_t gpa; + uint64_t hva; +} __aligned(PAGE_SIZE); + +struct guest_apic_pages { + struct guest_apic_page guest_apic_page[KVM_MAX_VCPUS]; +}; + +static struct guest_apic_pages *apic_page_pool; + +enum lapic_lvt_entry { + LVT_TIMER, + LVT_THERMAL_MONITOR, + LVT_PERFORMANCE_COUNTER, + LVT_LINT0, + LVT_LINT1, + LVT_ERROR, + APIC_MAX_NR_LVT_ENTRIES, +}; + +#define MSR_AMD64_SECURE_AVIC_CONTROL 0xc0010138 + +#define APIC_LVTx(x) (APIC_LVTT + 0x10 * (x)) +#define MSR_AMD64_SECURE_AVIC_EN_BIT 0 +#define MSR_AMD64_SECURE_AVIC_ALLOWED_NMI_BIT 1 + +/* + * Initial pool of guest apic backing page. + */ +void guest_apic_pages_init(struct kvm_vm *vm) +{ + struct guest_apic_pages *g_pages; + struct guest_apic_page *entry; + vm_vaddr_t vaddr; + int i; + size_t sz = align_up(sizeof(struct guest_apic_pages), + vm_guest_mode_params[vm->mode].page_size); + + vaddr = vm_vaddr_alloc(vm, sz, KVM_UTIL_MIN_VADDR); + + g_pages = (struct guest_apic_pages *)addr_gva2hva(vm, vaddr); + memset(g_pages, 0, sz); + + for (i = 0; i < KVM_MAX_VCPUS; ++i) { + entry = &g_pages->guest_apic_page[i]; + entry->hva = (uint64_t)entry; + entry->gpa = (uint64_t)addr_hva2gpa(vm, &entry->apic_page); + } + + apic_page_pool = (struct guest_apic_pages *)vaddr; + sync_global_to_guest(vm, apic_page_pool); +} + +int savic_nr_pages_required(uint64_t page_size) +{ + return align_up(sizeof(struct guest_apic_pages), page_size) / page_size; +} + +/* + * Enable/disable Secure AVIC in control msr. + * + * @apic_page : Guest APIC backing page for the CPU on which + * this function is called. + * @enable : Enable/Disable Secure AVIC. + * @enable_nmi : Allow host to send NMI to the guest. + */ +void set_savic_control_msr(struct guest_apic_page *apic_page, bool enable, bool enable_nmi) +{ + uint64_t val = apic_page->gpa | BIT_ULL(MSR_AMD64_SECURE_AVIC_EN_BIT); + + if (!enable) { + wrmsr(MSR_AMD64_SECURE_AVIC_CONTROL, 0); + return; + } + + if (enable_nmi) + val |= BIT_ULL(MSR_AMD64_SECURE_AVIC_ALLOWED_NMI_BIT); + + wrmsr(MSR_AMD64_SECURE_AVIC_CONTROL, val); +} + +/* + * Write APIC reg offset in the guest APIC backing page. + * + * @apage : Backing page address. + * @reg : APIC reg offset corresponding to the xapic MMIO + * offset. + * @val : New value to be set for the APIC reg. + */ +void savic_write_reg(struct guest_apic_page *apic_page, uint32_t reg, uint64_t val) +{ + *(volatile uint64_t *)((uint64_t)apic_page + reg) = val; +} + +/* + * Read APIC reg offset from the guest APIC backing page. + * + * @apage : Backing page address. + * @reg : APIC reg offset corresponding to the xapic MMIO + * offset. + * + * @ret : APIC register value in the guest APIC backing page. + */ +uint64_t savic_read_reg(struct guest_apic_page *apic_page, uint32_t reg) +{ + return *(volatile uint64_t *)((uint64_t)apic_page + reg); +} + +/* + * Write APIC reg value to hypervisor. + * + * @reg : APIC reg offset corresponding to the xapic MMIO + * offset. + * @val : Value to be set for the APIC reg. + */ +void savic_hv_write_reg(uint32_t reg, uint64_t val) +{ + sev_es_pv_msr_rw(APIC_BASE_MSR + (reg >> 4), &val, true); +} + +/* + * Read APIC reg offset from hypervisor. + * + * @reg : APIC reg offset corresponding to the xapic MMIO + * offset. + * + * @ret : APIC register value in the hypervisor's APIC state. + */ +uint64_t savic_hv_read_reg(uint32_t reg) +{ + uint64_t val; + + sev_es_pv_msr_rw(APIC_BASE_MSR + (reg >> 4), &val, false); + + return val; +} + +static void savic_init_backing_page(struct guest_apic_page *apic_page, uint32_t apic_id) +{ + uint64_t regval; + enum lapic_lvt_entry i; + + /* Update APIC ID in the backing page */ + savic_write_reg(apic_page, APIC_ID, apic_id); + + /* Set LVR, LDR, LVT* in backing page from host values */ + regval = savic_hv_read_reg(APIC_LVR); + savic_write_reg(apic_page, APIC_LVR, regval); + + regval = savic_hv_read_reg(APIC_LDR); + savic_write_reg(apic_page, APIC_LDR, regval); + + for (i = LVT_THERMAL_MONITOR; i < APIC_MAX_NR_LVT_ENTRIES; i++) { + regval = savic_hv_read_reg(APIC_LVTx(i)); + savic_write_reg(apic_page, APIC_LVTx(i), regval); + } + + regval = savic_hv_read_reg(APIC_LVT0); + savic_write_reg(apic_page, APIC_LVT0, regval); + + regval = savic_hv_read_reg(APIC_LVT1); + savic_write_reg(apic_page, APIC_LVT1, regval); +} + +/* + * Initialize and enable Secure AVIC on a CPU. + * + * @context: Called from x2apic enabled context and Secure AVIC disabled. + */ +void savic_enable(void) +{ + uint64_t savic_ctrl_msr_val, exp_msr_val; + struct guest_apic_page *apic_page; + uint32_t apic_id; + + __GUEST_ASSERT(apic_page_pool, "Guest APIC pages pool is not initialized"); + apic_id = x2apic_read_reg(APIC_ID); + apic_page = &apic_page_pool->guest_apic_page[apic_id]; + + savic_init_backing_page(apic_page, apic_id); + set_savic_control_msr(apic_page, true, true); + savic_ctrl_msr_val = rdmsr(MSR_AMD64_SECURE_AVIC_CONTROL); + exp_msr_val = apic_page->gpa | BIT_ULL(MSR_AMD64_SECURE_AVIC_EN_BIT) | + BIT_ULL(MSR_AMD64_SECURE_AVIC_ALLOWED_NMI_BIT); + __GUEST_ASSERT(savic_ctrl_msr_val == exp_msr_val, + "SAVIC Control msr unexpected val : 0x%lx, expected : 0x%lx", + savic_ctrl_msr_val, exp_msr_val); +} diff --git a/tools/testing/selftests/kvm/lib/x86/sev.c b/tools/testing/selftests/kvm/lib/x86/sev.c index 1e0719dfd6b0..113f33ca40b2 100644 --- a/tools/testing/selftests/kvm/lib/x86/sev.c +++ b/tools/testing/selftests/kvm/lib/x86/sev.c @@ -276,6 +276,18 @@ struct kvm_vm *vm_sev_create_with_one_vcpu(uint32_t type, void *guest_code, return vm; }
+static bool is_savic_enabled(void) +{ + u64 supported_vmsa_features; + int kvm_fd = open_kvm_dev_path_or_exit(); + + kvm_device_attr_get(kvm_fd, KVM_X86_GRP_SEV, + KVM_X86_SEV_VMSA_FEATURES, + &supported_vmsa_features); + + return supported_vmsa_features & BIT_ULL(SVM_FEAT_SECURE_AVIC); +} + void vm_sev_launch(struct kvm_vm *vm, uint64_t policy, uint8_t *measurement) { if (is_sev_es_vm(vm)) @@ -284,6 +296,9 @@ void vm_sev_launch(struct kvm_vm *vm, uint64_t policy, uint8_t *measurement) if (is_sev_snp_vm(vm)) { vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, BIT(KVM_HC_MAP_GPA_RANGE));
+ if (is_savic_enabled()) + guest_apic_pages_init(vm); + snp_vm_launch_start(vm, policy);
snp_vm_launch_update(vm);