On 12/14/20 10:03 AM, Paolo Bonzini wrote:
> On 10/12/20 18:10, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
>>
>> Typically under KVM, an AP is booted using the INIT-SIPI-SIPI sequence,
>> where the guest vCPU register state is updated and then the vCPU is VMRUN
>> to begin execution of the AP. For an SEV-ES guest, this won't work because
>> the guest register state is encrypted.
>>
>> Following the GHCB specification, the hypervisor must not alter the guest
>> register state, so KVM must track an AP/vCPU boot. Should the guest want
>> to park the AP, it must use the AP Reset Hold exit event in place of, for
>> example, a HLT loop.
>>
>> First AP boot (first INIT-SIPI-SIPI sequence):
>> Execute the AP (vCPU) as it was initialized and measured by the SEV-ES
>> support. It is up to the guest to transfer control of the AP to the
>> proper location.
>>
>> Subsequent AP boot:
>> KVM will expect to receive an AP Reset Hold exit event indicating that
>> the vCPU is being parked and will require an INIT-SIPI-SIPI sequence to
>> awaken it. When the AP Reset Hold exit event is received, KVM will place
>> the vCPU into a simulated HLT mode. Upon receiving the INIT-SIPI-SIPI
>> sequence, KVM will make the vCPU runnable. It is again up to the guest
>> to then transfer control of the AP to the proper location.
>>
>> The GHCB specification also requires the hypervisor to save the address of
>> an AP Jump Table so that, for example, vCPUs that have been parked by UEFI
>> can be started by the OS. Provide support for the AP Jump Table set/get
>> exit code.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
>> ---
>> arch/x86/include/asm/kvm_host.h | 2 ++
>> arch/x86/kvm/svm/sev.c | 50 +++++++++++++++++++++++++++++++++
>> arch/x86/kvm/svm/svm.c | 7 +++++
>> arch/x86/kvm/svm/svm.h | 3 ++
>> arch/x86/kvm/x86.c | 9 ++++++
>> 5 files changed, 71 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h
>> b/arch/x86/include/asm/kvm_host.h
>> index 048b08437c33..60a3b9d33407 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -1286,6 +1286,8 @@ struct kvm_x86_ops {
>> void (*migrate_timers)(struct kvm_vcpu *vcpu);
>> void (*msr_filter_changed)(struct kvm_vcpu *vcpu);
>> +
>> + void (*vcpu_deliver_sipi_vector)(struct kvm_vcpu *vcpu, u8 vector);
>> };
>> struct kvm_x86_nested_ops {
>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
>> index a7531de760b5..b47285384b1f 100644
>> --- a/arch/x86/kvm/svm/sev.c
>> +++ b/arch/x86/kvm/svm/sev.c
>> @@ -17,6 +17,8 @@
>> #include <linux/processor.h>
>> #include <linux/trace_events.h>
>> +#include <asm/trapnr.h>
>> +
>> #include "x86.h"
>> #include "svm.h"
>> #include "cpuid.h"
>> @@ -1449,6 +1451,8 @@ static int sev_es_validate_vmgexit(struct vcpu_svm
>> *svm)
>> if (!ghcb_sw_scratch_is_valid(ghcb))
>> goto vmgexit_err;
>> break;
>> + case SVM_VMGEXIT_AP_HLT_LOOP:
>> + case SVM_VMGEXIT_AP_JUMP_TABLE:
>> case SVM_VMGEXIT_UNSUPPORTED_EVENT:
>> break;
>> default:
>> @@ -1770,6 +1774,35 @@ int sev_handle_vmgexit(struct vcpu_svm *svm)
>> control->exit_info_2,
>> svm->ghcb_sa);
>> break;
>> + case SVM_VMGEXIT_AP_HLT_LOOP:
>> + svm->ap_hlt_loop = true;
>
> This value needs to be communicated to userspace. Let's get this right
> from the beginning and use a new KVM_MP_STATE_* value instead (perhaps
> reuse KVM_MP_STATE_STOPPED but for x86 #define it as
> KVM_MP_STATE_AP_HOLD_RECEIVED?).
Ok, let me look into this.
>
>> @@ -68,6 +68,7 @@ struct kvm_sev_info {
>> int fd; /* SEV device fd */
>> unsigned long pages_locked; /* Number of pages locked */
>> struct list_head regions_list; /* List of registered regions */
>> + u64 ap_jump_table; /* SEV-ES AP Jump Table address */
>
> Do you have any plans for migration of this value? How does the guest
> ensure that the hypervisor does not screw with it?
I'll be sure that this is part of the SEV-ES live migration support.
For SEV-ES, we can't guarantee that the hypervisor doesn't screw with it.
This is something that SEV-SNP will be able to address.
Thanks,
Tom
>
> Paolo
>
