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

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

On 11/18/2023 5:18 AM, Isaku Yamahata wrote:
> On Wed, Nov 15, 2023 at 02:14:27AM -0500,
> Xiaoyao Li <xiaoyao.li@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> > 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.