Re: [PATCH v3 18/70] i386/tdx: Get tdx_capabilities via KVM_TDX_CAPABILITIES

Xiaoyao Li
2023-12-07T07:17:15Z

On 11/18/2023 5:18 AM, Isaku Yamahata wrote:
> On Wed, Nov 15, 2023 at 02:14:27AM -0500,
> Xiaoyao Li <xiaoyao.li@intel.com> wrote:
>
>> KVM provides TDX capabilities via sub command KVM_TDX_CAPABILITIES of
>> IOCTL(KVM_MEMORY_ENCRYPT_OP). Get the capabilities when initializing
>> TDX context. It will be used to validate user's setting later.
>>
>> Since there is no interface reporting how many cpuid configs contains in
>> KVM_TDX_CAPABILITIES, QEMU chooses to try starting with a known number
>> and abort when it exceeds KVM_MAX_CPUID_ENTRIES.
>>
>> Besides, introduce the interfaces to invoke TDX "ioctls" at different
>> scope (KVM, VM and VCPU) in preparation.
>>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> ---
>> Changes in v3:
>> - rename __tdx_ioctl() to tdx_ioctl_internal()
>> - Pass errp in get_tdx_capabilities();
>>
>> changes in v2:
>> - Make the error message more clear;
>>
>> changes in v1:
>> - start from nr_cpuid_configs = 6 for the loop;
>> - stop the loop when nr_cpuid_configs exceeds KVM_MAX_CPUID_ENTRIES;
>> ---
>> target/i386/kvm/kvm.c | 2 -
>> target/i386/kvm/kvm_i386.h | 2 +
>> target/i386/kvm/tdx.c | 102 ++++++++++++++++++++++++++++++++++++-
>> 3 files changed, 103 insertions(+), 3 deletions(-)
>>
>> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
>> index 7abcdebb1452..28e60c5ea4a7 100644
>> --- a/target/i386/kvm/kvm.c
>> +++ b/target/i386/kvm/kvm.c
>> @@ -1687,8 +1687,6 @@ static int hyperv_init_vcpu(X86CPU *cpu)
>>
>> static Error *invtsc_mig_blocker;
>>
>> -#define KVM_MAX_CPUID_ENTRIES 100
>> -
>> static void kvm_init_xsave(CPUX86State *env)
>> {
>> if (has_xsave2) {
>> diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
>> index 55fb25fa8e2e..c3ef46a97a7b 100644
>> --- a/target/i386/kvm/kvm_i386.h
>> +++ b/target/i386/kvm/kvm_i386.h
>> @@ -13,6 +13,8 @@
>>
>> #include "sysemu/kvm.h"
>>
>> +#define KVM_MAX_CPUID_ENTRIES 100
>> +
>> #ifdef CONFIG_KVM
>>
>> #define kvm_pit_in_kernel() \
>> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
>> index 621a05beeb4e..cb0040187b27 100644
>> --- a/target/i386/kvm/tdx.c
>> +++ b/target/i386/kvm/tdx.c
>> @@ -12,17 +12,117 @@
>> */
>>
>> #include "qemu/osdep.h"
>> +#include "qemu/error-report.h"
>> #include "qapi/error.h"
>> #include "qom/object_interfaces.h"
>> +#include "sysemu/kvm.h"
>>
>> #include "hw/i386/x86.h"
>> +#include "kvm_i386.h"
>> #include "tdx.h"
>>
>> +static struct kvm_tdx_capabilities *tdx_caps;
>> +
>> +enum tdx_ioctl_level{
>> + TDX_PLATFORM_IOCTL,
>> + TDX_VM_IOCTL,
>> + TDX_VCPU_IOCTL,
>> +};
>> +
>> +static int tdx_ioctl_internal(void *state, enum tdx_ioctl_level level, int cmd_id,
>> + __u32 flags, void *data)
>> +{
>> + struct kvm_tdx_cmd tdx_cmd;
>> + int r;
>> +
>> + memset(&tdx_cmd, 0x0, sizeof(tdx_cmd));
>> +
>> + tdx_cmd.id = cmd_id;
>> + tdx_cmd.flags = flags;
>> + tdx_cmd.data = (__u64)(unsigned long)data;
>> +
>> + switch (level) {
>> + case TDX_PLATFORM_IOCTL:
>> + r = kvm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
>> + break;
>> + case TDX_VM_IOCTL:
>> + r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
>> + break;
>> + case TDX_VCPU_IOCTL:
>> + r = kvm_vcpu_ioctl(state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
>> + break;
>> + default:
>> + error_report("Invalid tdx_ioctl_level %d", level);
>> + exit(1);
>> + }
>> +
>> + return r;
>> +}
>> +
>> +static inline int tdx_platform_ioctl(int cmd_id, __u32 flags, void *data)
>> +{
>> + return tdx_ioctl_internal(NULL, TDX_PLATFORM_IOCTL, cmd_id, flags, data);
>> +}
>> +
>> +static inline int tdx_vm_ioctl(int cmd_id, __u32 flags, void *data)
>> +{
>> + return tdx_ioctl_internal(NULL, TDX_VM_IOCTL, cmd_id, flags, data);
>> +}
>> +
>> +static inline int tdx_vcpu_ioctl(void *vcpu_fd, int cmd_id, __u32 flags,
>> + void *data)
>> +{
>> + return tdx_ioctl_internal(vcpu_fd, TDX_VCPU_IOCTL, cmd_id, flags, data);
>> +}
>
> As all of ioctl variants aren't used yet, we can split out them.

No. tdx_vm_ioctl() is used right below.

I can remove the tdx_platform_ioctl() because its sole user,
KVM_TDX_CAPABILITIES, changed to vm scope.

> An independent
> patch to define ioctl functions.
>
>
>> +
>> +static int get_tdx_capabilities(Error **errp)
>> +{
>> + struct kvm_tdx_capabilities *caps;
>> + /* 1st generation of TDX reports 6 cpuid configs */
>> + int nr_cpuid_configs = 6;
>> + size_t size;
>> + int r;
>> +
>> + do {
>> + size = sizeof(struct kvm_tdx_capabilities) +
>> + nr_cpuid_configs * sizeof(struct kvm_tdx_cpuid_config);
>> + caps = g_malloc0(size);
>> + caps->nr_cpuid_configs = nr_cpuid_configs;
>> +
>> + r = tdx_vm_ioctl(KVM_TDX_CAPABILITIES, 0, caps);
>> + if (r == -E2BIG) {
>> + g_free(caps);
>> + nr_cpuid_configs *= 2;
>
> g_realloc()? Maybe a matter of preference.

I would like to keep the current code unless strong objection from
maintainers.

> Other than this, it looks good to me.