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KVM: track whether guest state is encrypted

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So far, KVM has allowed KVM_GET/SET_* ioctls to execute even if the
guest state is encrypted, in which case they do nothing.  For the new
API using VM types, instead, the ioctls will fail which is a safer and
more robust approach.

The new API will be the only one available for SEV-SNP and TDX, but it
is also usable for SEV and SEV-ES.  In preparation for that, require
architecture-specific KVM code to communicate the point at which guest
state is protected (which must be after kvm_cpu_synchronize_post_init(),
though that might change in the future in order to suppor migration).
From that point, skip reading registers so that cpu->vcpu_dirty is
never true: if it ever becomes true, kvm_arch_put_registers() will
fail miserably.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-03-18 14:41:10 -04:00
parent 08b2d15cdd
commit 5c3131c392
4 changed files with 18 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

17
accel/kvm/kvm-all.c
View file

@ -2703,7 +2703,7 @@ bool kvm_cpu_check_are_resettable(void)
static void do_kvm_cpu_synchronize_state(CPUState *cpu, run_on_cpu_data arg)
{
if (!cpu->vcpu_dirty) {
if (!cpu->vcpu_dirty && !kvm_state->guest_state_protected) {
int ret = kvm_arch_get_registers(cpu);
if (ret) {
error_report("Failed to get registers: %s", strerror(-ret));
@ -2717,7 +2717,7 @@ static void do_kvm_cpu_synchronize_state(CPUState *cpu, run_on_cpu_data arg)
void kvm_cpu_synchronize_state(CPUState *cpu)
{
if (!cpu->vcpu_dirty) {
if (!cpu->vcpu_dirty && !kvm_state->guest_state_protected) {
run_on_cpu(cpu, do_kvm_cpu_synchronize_state, RUN_ON_CPU_NULL);
}
}
@ -2752,7 +2752,13 @@ static void do_kvm_cpu_synchronize_post_init(CPUState *cpu, run_on_cpu_data arg)
void kvm_cpu_synchronize_post_init(CPUState *cpu)
{
run_on_cpu(cpu, do_kvm_cpu_synchronize_post_init, RUN_ON_CPU_NULL);
if (!kvm_state->guest_state_protected) {
/*
* This runs before the machine_init_done notifiers, and is the last
* opportunity to synchronize the state of confidential guests.
*/
run_on_cpu(cpu, do_kvm_cpu_synchronize_post_init, RUN_ON_CPU_NULL);
}
}
static void do_kvm_cpu_synchronize_pre_loadvm(CPUState *cpu, run_on_cpu_data arg)
@ -4099,3 +4105,8 @@ void query_stats_schemas_cb(StatsSchemaList **result, Error **errp)
query_stats_schema_vcpu(first_cpu, &stats_args);
}
}
void kvm_mark_guest_state_protected(void)
{
kvm_state->guest_state_protected = true;
}