On 2021-01-26 11:36:46 -0600, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
>
> When SEV-ES is enabled, it is not possible modify the guests register
> state after it has been initially created, encrypted and measured.
>
> Normally, an INIT-SIPI-SIPI request is used to boot the AP. However, the
> hypervisor cannot emulate this because it cannot update the AP register
> state. For the very first boot by an AP, the reset vector CS segment
> value and the EIP value must be programmed before the register has been
> encrypted and measured. Search the guest firmware for the guest for a
> specific GUID that tells Qemu the value of the reset vector to use.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@xxxxxxxxx>
> Cc: Richard Henderson <richard.henderson@xxxxxxxxxx>
> Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> accel/kvm/kvm-all.c | 64 ++++++++++++++++++++++++++++++++++++
> accel/stubs/kvm-stub.c | 5 +++
> hw/i386/pc_sysfw.c | 10 +++++-
> include/sysemu/kvm.h | 16 +++++++++
> include/sysemu/sev.h | 3 ++
> target/i386/kvm/kvm.c | 2 ++
> target/i386/sev.c | 74 ++++++++++++++++++++++++++++++++++++++++++
> 7 files changed, 173 insertions(+), 1 deletion(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 3feb17d965..410879cf94 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -39,6 +39,7 @@
> #include "qemu/main-loop.h"
> #include "trace.h"
> #include "hw/irq.h"
> +#include "sysemu/kvm.h"
> #include "sysemu/sev.h"
> #include "qapi/visitor.h"
> #include "qapi/qapi-types-common.h"
> @@ -126,6 +127,12 @@ struct KVMState
> /* memory encryption */
> void *memcrypt_handle;
> int (*memcrypt_encrypt_data)(void *handle, uint8_t *ptr, uint64_t len);
> + int (*memcrypt_save_reset_vector)(void *handle, void *flash_ptr,
> + uint64_t flash_size, uint32_t *addr);
> +
> + uint32_t reset_cs;
> + uint32_t reset_ip;
> + bool reset_data_valid;
>
> /* For "info mtree -f" to tell if an MR is registered in KVM */
> int nr_as;
> @@ -245,6 +252,62 @@ int kvm_memcrypt_encrypt_data(uint8_t *ptr, uint64_t len)
> return 1;
> }
>
> +void kvm_memcrypt_set_reset_vector(CPUState *cpu)
> +{
> + X86CPU *x86;
> + CPUX86State *env;
> +
> + /* Only update if we have valid reset information */
> + if (!kvm_state->reset_data_valid) {
> + return;
> + }
> +
> + /* Do not update the BSP reset state */
> + if (cpu->cpu_index == 0) {
> + return;
> + }
> +
> + x86 = X86_CPU(cpu);
> + env = &x86->env;
> +
> + cpu_x86_load_seg_cache(env, R_CS, 0xf000, kvm_state->reset_cs, 0xffff,
> + DESC_P_MASK | DESC_S_MASK | DESC_CS_MASK |
> + DESC_R_MASK | DESC_A_MASK);
> +
> + env->eip = kvm_state->reset_ip;
> +}
> +
> +int kvm_memcrypt_save_reset_vector(void *flash_ptr, uint64_t flash_size)
> +{
> + CPUState *cpu;
> + uint32_t addr;
> + int ret;
> +
> + if (kvm_memcrypt_enabled() &&
> + kvm_state->memcrypt_save_reset_vector) {
> +
> + addr = 0;
> + ret = kvm_state->memcrypt_save_reset_vector(kvm_state->memcrypt_handle,
> + flash_ptr, flash_size,
> + &addr);
> + if (ret) {
> + return ret;
> + }
> +
> + if (addr) {
> + kvm_state->reset_cs = addr & 0xffff0000;
> + kvm_state->reset_ip = addr & 0x0000ffff;
> + kvm_state->reset_data_valid = true;
> +
> + CPU_FOREACH(cpu) {
> + kvm_memcrypt_set_reset_vector(cpu);
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> /* Called with KVMMemoryListener.slots_lock held */
> static KVMSlot *kvm_get_free_slot(KVMMemoryListener *kml)
> {
> @@ -2216,6 +2279,7 @@ static int kvm_init(MachineState *ms)
> }
>
> kvm_state->memcrypt_encrypt_data = sev_encrypt_data;
> + kvm_state->memcrypt_save_reset_vector = sev_es_save_reset_vector;
> }
>
> ret = kvm_arch_init(ms, s);
> diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c
> index 680e099463..162c28429e 100644
> --- a/accel/stubs/kvm-stub.c
> +++ b/accel/stubs/kvm-stub.c
> @@ -91,6 +91,11 @@ int kvm_memcrypt_encrypt_data(uint8_t *ptr, uint64_t len)
> return 1;
> }
>
> +int kvm_memcrypt_save_reset_vector(void *flash_ptr, uint64_t flash_size)
> +{
> + return -ENOSYS;
> +}
> +
> #ifndef CONFIG_USER_ONLY
> int kvm_irqchip_add_msi_route(KVMState *s, int vector, PCIDevice *dev)
> {
> diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
> index 436b78c587..edec28842d 100644
> --- a/hw/i386/pc_sysfw.c
> +++ b/hw/i386/pc_sysfw.c
> @@ -248,7 +248,8 @@ static void pc_system_flash_map(PCMachineState *pcms,
> PFlashCFI01 *system_flash;
> MemoryRegion *flash_mem;
> void *flash_ptr;
> - int ret, flash_size;
> + uint64_t flash_size;
> + int ret;
>
> assert(PC_MACHINE_GET_CLASS(pcms)->pci_enabled);
>
> @@ -301,6 +302,13 @@ static void pc_system_flash_map(PCMachineState *pcms,
> * search for them
> */
> pc_system_parse_ovmf_flash(flash_ptr, flash_size);
> +
> + ret = kvm_memcrypt_save_reset_vector(flash_ptr, flash_size);
> + if (ret) {
> + error_report("failed to locate and/or save reset vector");
> + exit(1);
> + }
> +
> ret = kvm_memcrypt_encrypt_data(flash_ptr, flash_size);
> if (ret) {
> error_report("failed to encrypt pflash rom");
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index bb5d5cf497..875ca101e3 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -249,6 +249,22 @@ bool kvm_memcrypt_enabled(void);
> */
> int kvm_memcrypt_encrypt_data(uint8_t *ptr, uint64_t len);
>
> +/**
> + * kvm_memcrypt_set_reset_vector - sets the CS/IP value for the AP if SEV-ES
> + * is active.
> + */
> +void kvm_memcrypt_set_reset_vector(CPUState *cpu);
> +
> +/**
> + * kvm_memcrypt_save_reset_vector - locates and saves the reset vector to be
> + * used as the initial CS/IP value for APs
> + * if SEV-ES is active.
> + *
> + * Return: 1 SEV-ES is active and failed to locate a valid reset vector
> + * 0 SEV-ES is not active or successfully located and saved the
> + * reset vector address
> + */
> +int kvm_memcrypt_save_reset_vector(void *flash_prt, uint64_t flash_size);
>
> #ifdef NEED_CPU_H
> #include "cpu.h"
> diff --git a/include/sysemu/sev.h b/include/sysemu/sev.h
> index 7ab6e3e31d..6f5ad3fd03 100644
> --- a/include/sysemu/sev.h
> +++ b/include/sysemu/sev.h
> @@ -20,4 +20,7 @@ void *sev_guest_init(const char *id);
> int sev_encrypt_data(void *handle, uint8_t *ptr, uint64_t len);
> int sev_inject_launch_secret(const char *hdr, const char *secret,
> uint64_t gpa, Error **errp);
> +int sev_es_save_reset_vector(void *handle, void *flash_ptr,
> + uint64_t flash_size, uint32_t *addr);
> +
> #endif
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index 6dc1ee052d..aaae79557d 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -1920,6 +1920,8 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
> }
> /* enabled by default */
> env->poll_control_msr = 1;
> +
> + kvm_memcrypt_set_reset_vector(CPU(cpu));
> }
>
> void kvm_arch_do_init_vcpu(X86CPU *cpu)
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index ddec7ebaa7..badc141554 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -22,6 +22,7 @@
> #include "qom/object_interfaces.h"
> #include "qemu/base64.h"
> #include "qemu/module.h"
> +#include "qemu/uuid.h"
> #include "sysemu/kvm.h"
> #include "sev_i386.h"
> #include "sysemu/sysemu.h"
> @@ -31,6 +32,7 @@
> #include "qom/object.h"
> #include "exec/address-spaces.h"
> #include "monitor/monitor.h"
> +#include "hw/i386/pc.h"
>
> #define TYPE_SEV_GUEST "sev-guest"
> OBJECT_DECLARE_SIMPLE_TYPE(SevGuestState, SEV_GUEST)
> @@ -71,6 +73,12 @@ struct SevGuestState {
> #define DEFAULT_GUEST_POLICY 0x1 /* disable debug */
> #define DEFAULT_SEV_DEVICE "/dev/sev"
>
> +#define SEV_INFO_BLOCK_GUID "00f771de-1a7e-4fcb-890e-68c77e2fb44e"
> +typedef struct __attribute__((__packed__)) SevInfoBlock {
> + /* SEV-ES Reset Vector Address */
> + uint32_t reset_addr;
> +} SevInfoBlock;
> +
> static SevGuestState *sev_guest;
> static Error *sev_mig_blocker;
>
> @@ -896,6 +904,72 @@ int sev_inject_launch_secret(const char *packet_hdr, const char *secret,
> return 0;
> }
>
> +static int
> +sev_es_parse_reset_block(SevInfoBlock *info, uint32_t *addr)
> +{
> + if (!info->reset_addr) {
> + error_report("SEV-ES reset address is zero");
> + return 1;
> + }
> +
> + *addr = info->reset_addr;
> +
> + return 0;
> +}
> +
> +int
> +sev_es_save_reset_vector(void *handle, void *flash_ptr, uint64_t flash_size,
> + uint32_t *addr)
> +{
> + QemuUUID info_guid, *guid;
> + SevInfoBlock *info;
> + uint8_t *data;
> + uint16_t *len;
> +
> + assert(handle);
> +
> + /*
> + * Initialize the address to zero. An address of zero with a successful
> + * return code indicates that SEV-ES is not active.
> + */
> + *addr = 0;
> + if (!sev_es_enabled()) {
> + return 0;
> + }
> +
> + /*
> + * Extract the AP reset vector for SEV-ES guests by locating the SEV GUID.
> + * The SEV GUID is located on its own (original implementation) or within
> + * the Firmware GUID Table (new implementation), either of which are
> + * located 32 bytes from the end of the flash.
> + *
> + * Check the Firmware GUID Table first.
> + */
> + if (pc_system_ovmf_table_find(SEV_INFO_BLOCK_GUID, &data, NULL)) {
> + return sev_es_parse_reset_block((SevInfoBlock *)data, addr);
> + }
> +
> + /*
> + * SEV info block not found in the Firmware GUID Table (or there isn't
> + * a Firmware GUID Table), fall back to the original implementation.
> + */
> + data = flash_ptr + flash_size - 0x20;
Even if the SEV_INFO_BLOCK_GUID is always located at 32 bytes from the end
of the flash, isn't it better to define a constant with a value of 0x20?
> +
> + qemu_uuid_parse(SEV_INFO_BLOCK_GUID, &info_guid);
> + info_guid = qemu_uuid_bswap(info_guid); /* GUIDs are LE */
> +
> + guid = (QemuUUID *)(data - sizeof(info_guid));
> + if (!qemu_uuid_is_equal(guid, &info_guid)) {
> + error_report("SEV information block/Firmware GUID Table block not found in pflash rom");
> + return 1;
> + }
> +
> + len = (uint16_t *)((uint8_t *)guid - sizeof(*len));
> + info = (SevInfoBlock *)(data - le16_to_cpu(*len));
> +
> + return sev_es_parse_reset_block(info, addr);
> +}
> +
> static void
> sev_register_types(void)
> {
> --
> 2.30.0
>
