[PATCH v6 09/60] i386/tdx: Initialize TDX before creating TD vcpus

Xiaoyao Li
2024-11-05T06:37:04Z

Invoke KVM_TDX_INIT in kvm_arch_pre_create_vcpu() that KVM_TDX_INIT
configures global TD configurations, e.g. the canonical CPUID config,
and must be executed prior to creating vCPUs.

Use kvm_x86_arch_cpuid() to setup the CPUID settings for TDX VM.

Note, this doesn't address the fact that QEMU may change the CPUID
configuration when creating vCPUs, i.e. punts on refactoring QEMU to
provide a stable CPUID config prior to kvm_arch_init().

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
---
Changes in v6:
- setup xfam explicitly to fit with new uapi;
- use tdx_caps->cpuid to filter the input of cpuids because now KVM only
allows the leafs that reported via KVM_TDX_GET_CAPABILITIES;

Changes in v4:
- mark init_vm with g_autofree() and use QEMU_LOCK_GUARD() to eliminate
the goto labels; (Daniel)
Changes in v3:
- Pass @errp in tdx_pre_create_vcpu() and pass error info to it. (Daniel)
---
accel/kvm/kvm-all.c | 8 ++++
target/i386/kvm/kvm.c | 15 +++++--
target/i386/kvm/kvm_i386.h | 3 ++
target/i386/kvm/meson.build | 2 +-
target/i386/kvm/tdx-stub.c | 8 ++++
target/i386/kvm/tdx.c | 87 +++++++++++++++++++++++++++++++++++++
target/i386/kvm/tdx.h | 6 +++
7 files changed, 125 insertions(+), 4 deletions(-)
create mode 100644 target/i386/kvm/tdx-stub.c

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 1732fa1adecd..4a1c9950894c 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -536,8 +536,15 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)

trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));

+ /*
+ * tdx_pre_create_vcpu() may call cpu_x86_cpuid(). It in turn may call
+ * kvm_vm_ioctl(). Set cpu->kvm_state in advance to avoid NULL pointer
+ * dereference.
+ */
+ cpu->kvm_state = s;
ret = kvm_arch_pre_create_vcpu(cpu, errp);
if (ret < 0) {
+ cpu->kvm_state = NULL;
goto err;
}

@@ -546,6 +553,7 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
error_setg_errno(errp, -ret,
"kvm_init_vcpu: kvm_create_vcpu failed (%lu)",
kvm_arch_vcpu_id(cpu));
+ cpu->kvm_state = NULL;
goto err;
}

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index afbf67a7fdaa..db676c1336ab 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -38,6 +38,7 @@
#include "kvm_i386.h"
#include "../confidential-guest.h"
#include "sev.h"
+#include "tdx.h"
#include "xen-emu.h"
#include "hyperv.h"
#include "hyperv-proto.h"
@@ -1824,9 +1825,8 @@ static void kvm_init_nested_state(CPUX86State *env)
}
}

-static uint32_t kvm_x86_build_cpuid(CPUX86State *env,
- struct kvm_cpuid_entry2 *entries,
- uint32_t cpuid_i)
+uint32_t kvm_x86_build_cpuid(CPUX86State *env, struct kvm_cpuid_entry2 *entries,
+ uint32_t cpuid_i)
{
uint32_t limit, i, j;
uint32_t unused;
@@ -2358,6 +2358,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
return r;
}

+int kvm_arch_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+ if (is_tdx_vm()) {
+ return tdx_pre_create_vcpu(cpu, errp);
+ }
+
+ return 0;
+}
+
int kvm_arch_destroy_vcpu(CPUState *cs)
{
X86CPU *cpu = X86_CPU(cs);
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index efb0883bd968..b1baf9e7f910 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -24,6 +24,9 @@
#define kvm_ioapic_in_kernel() \
(kvm_irqchip_in_kernel() && !kvm_irqchip_is_split())

+uint32_t kvm_x86_build_cpuid(CPUX86State *env, struct kvm_cpuid_entry2 *entries,
+ uint32_t cpuid_i);
+
#else

#define kvm_pit_in_kernel() 0
diff --git a/target/i386/kvm/meson.build b/target/i386/kvm/meson.build
index 466bccb9cb17..3f44cdedb758 100644
--- a/target/i386/kvm/meson.build
+++ b/target/i386/kvm/meson.build
@@ -8,7 +8,7 @@ i386_kvm_ss.add(files(

i386_kvm_ss.add(when: 'CONFIG_XEN_EMU', if_true: files('xen-emu.c'))

-i386_kvm_ss.add(when: 'CONFIG_TDX', if_true: files('tdx.c'))
+i386_kvm_ss.add(when: 'CONFIG_TDX', if_true: files('tdx.c'), if_false: files('tdx-stub.c'))

i386_system_ss.add(when: 'CONFIG_HYPERV', if_true: files('hyperv.c'), if_false: files('hyperv-stub.c'))

diff --git a/target/i386/kvm/tdx-stub.c b/target/i386/kvm/tdx-stub.c
new file mode 100644
index 000000000000..b614b46d3f4a
--- /dev/null
+++ b/target/i386/kvm/tdx-stub.c
@@ -0,0 +1,8 @@
+#include "qemu/osdep.h"
+
+#include "tdx.h"
+
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+ return -EINVAL;
+}
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index ff3ef9bd8657..1b7894e43c6f 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -137,6 +137,91 @@ static int tdx_kvm_type(X86ConfidentialGuest *cg)
return KVM_X86_TDX_VM;
}

+static int setup_td_xfam(X86CPU *x86cpu, Error **errp)
+{
+ CPUX86State *env = &x86cpu->env;
+ uint64_t xfam;
+
+ xfam = env->features[FEAT_XSAVE_XCR0_LO] |
+ env->features[FEAT_XSAVE_XCR0_HI] |
+ env->features[FEAT_XSAVE_XSS_LO] |
+ env->features[FEAT_XSAVE_XSS_HI];
+
+ if (xfam & ~tdx_caps->supported_xfam) {
+ error_setg(errp, "Invalid XFAM 0x%lx for TDX VM (supported: 0x%llx))",
+ xfam, tdx_caps->supported_xfam);
+ return -1;
+ }
+
+ tdx_guest->xfam = xfam;
+ return 0;
+}
+
+static void tdx_filter_cpuid(struct kvm_cpuid2 *cpuids)
+{
+ int i, dest_cnt = 0;
+ struct kvm_cpuid_entry2 *src, *dest, *conf;
+
+ for (i = 0; i < cpuids->nent; i++) {
+ src = cpuids->entries + i;
+ conf = cpuid_find_entry(&tdx_caps->cpuid, src->function, src->index);
+ if (!conf) {
+ continue;
+ }
+ dest = cpuids->entries + dest_cnt;
+
+ dest->function = src->function;
+ dest->index = src->index;
+ dest->flags = src->flags;
+ dest->eax = src->eax & conf->eax;
+ dest->ebx = src->ebx & conf->ebx;
+ dest->ecx = src->ecx & conf->ecx;
+ dest->edx = src->edx & conf->edx;
+
+ dest_cnt++;
+ }
+ cpuids->nent = dest_cnt++;
+}
+
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+ X86CPU *x86cpu = X86_CPU(cpu);
+ CPUX86State *env = &x86cpu->env;
+ g_autofree struct kvm_tdx_init_vm *init_vm = NULL;
+ int r = 0;
+
+ QEMU_LOCK_GUARD(&tdx_guest->lock);
+ if (tdx_guest->initialized) {
+ return r;
+ }
+
+ init_vm = g_malloc0(sizeof(struct kvm_tdx_init_vm) +
+ sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES);
+
+ r = setup_td_xfam(x86cpu, errp);
+ if (r) {
+ return r;
+ }
+
+ init_vm->cpuid.nent = kvm_x86_build_cpuid(env, init_vm->cpuid.entries, 0);
+ tdx_filter_cpuid(&init_vm->cpuid);
+
+ init_vm->attributes = tdx_guest->attributes;
+ init_vm->xfam = tdx_guest->xfam;
+
+ do {
+ r = tdx_vm_ioctl(KVM_TDX_INIT_VM, 0, init_vm);
+ } while (r == -EAGAIN);
+ if (r < 0) {
+ error_setg_errno(errp, -r, "KVM_TDX_INIT_VM failed");
+ return r;
+ }
+
+ tdx_guest->initialized = true;
+
+ return 0;
+}
+
/* tdx guest */
OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
tdx_guest,
@@ -150,6 +235,8 @@ static void tdx_guest_init(Object *obj)
ConfidentialGuestSupport *cgs = CONFIDENTIAL_GUEST_SUPPORT(obj);
TdxGuest *tdx = TDX_GUEST(obj);

+ qemu_mutex_init(&tdx->lock);
+
cgs->require_guest_memfd = true;
tdx->attributes = 0;

diff --git a/target/i386/kvm/tdx.h b/target/i386/kvm/tdx.h
index bca19c833e18..e077fd7d1653 100644
--- a/target/i386/kvm/tdx.h
+++ b/target/i386/kvm/tdx.h
@@ -17,7 +17,11 @@ typedef struct TdxGuestClass {
typedef struct TdxGuest {
X86ConfidentialGuest parent_obj;

+ QemuMutex lock;
+
+ bool initialized;
uint64_t attributes; /* TD attributes */
+ uint64_t xfam;
} TdxGuest;

#ifdef CONFIG_TDX
@@ -26,4 +30,6 @@ bool is_tdx_vm(void);
#define is_tdx_vm() 0
#endif /* CONFIG_TDX */

+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp);
+
#endif /* QEMU_I386_TDX_H */
--
2.34.1