Re: [PATCH v10 014/108] KVM: TDX: Stub in tdx.h with structs, accessors, and VMCS helpers

Isaku Yamahata
2022-11-03T00:57:50Z

On Mon, Oct 31, 2022 at 07:39:46PM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

>
> On 2022/10/30 14:22, isaku.yamahata@intel.com wrote:
> > From: Sean Christopherson <sean.j.christopherson@intel.com>
> >
> > Stub in kvm_tdx, vcpu_tdx, and their various accessors. TDX defines
> > SEAMCALL APIs to access TDX control structures corresponding to the VMX
> > VMCS. Introduce helper accessors to hide its SEAMCALL ABI details.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > ---
> > arch/x86/kvm/vmx/tdx.h | 118 ++++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 116 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> > index 473013265bd8..98999bf3f188 100644
> > --- a/arch/x86/kvm/vmx/tdx.h
> > +++ b/arch/x86/kvm/vmx/tdx.h
> > @@ -3,14 +3,27 @@
> > #define __KVM_X86_TDX_H
> > #ifdef CONFIG_INTEL_TDX_HOST
> > +
> > +#include "tdx_ops.h"
> > +
> > +struct tdx_td_page {
> > + unsigned long va;
> > + hpa_t pa;
> > + bool added;
> > +};
> > +
> > struct kvm_tdx {
> > struct kvm kvm;
> > - /* TDX specific members follow. */
> > +
> > + struct tdx_td_page tdr;
> > + struct tdx_td_page *tdcs;
> > };
> > struct vcpu_tdx {
> > struct kvm_vcpu vcpu;
> > - /* TDX specific members follow. */
> > +
> > + struct tdx_td_page tdvpr;
> > + struct tdx_td_page *tdvpx;
> > };
> > static inline bool is_td(struct kvm *kvm)
> > @@ -32,6 +45,107 @@ static inline struct vcpu_tdx *to_tdx(struct kvm_vcpu *vcpu)
> > {
> > return container_of(vcpu, struct vcpu_tdx, vcpu);
> > }
> > +
> > +static __always_inline void tdvps_vmcs_check(u32 field, u8 bits)
> > +{
> > +#define VMCS_ENC_ACCESS_TYPE_MASK 0x1UL
> > +#define VMCS_ENC_ACCESS_TYPE_FULL 0x0UL
> > +#define VMCS_ENC_ACCESS_TYPE_HIGH 0x1UL
> > +#define VMCS_ENC_ACCESS_TYPE(field) ((field) & VMCS_ENC_ACCESS_TYPE_MASK)
> > +
> > + /* TDX is 64bit only. HIGH field isn't supported. */
> > + BUILD_BUG_ON_MSG(__builtin_constant_p(field) &&
> > + VMCS_ENC_ACCESS_TYPE(field) == VMCS_ENC_ACCESS_TYPE_HIGH,
> > + "Read/Write to TD VMCS *_HIGH fields not supported");
> > +
> > + BUILD_BUG_ON(bits != 16 && bits != 32 && bits != 64);
> > +
> > +#define VMCS_ENC_WIDTH_MASK GENMASK(14, 13)
> > +#define VMCS_ENC_WIDTH_16BIT (0UL << 13)
> > +#define VMCS_ENC_WIDTH_64BIT (1UL << 13)
> > +#define VMCS_ENC_WIDTH_32BIT (2UL << 13)
> > +#define VMCS_ENC_WIDTH_NATURAL (3UL << 13)
> > +#define VMCS_ENC_WIDTH(field) ((field) & VMCS_ENC_WIDTH_MASK)
> > +
> > + /* TDX is 64bit only. i.e. natural width = 64bit. */
> > + BUILD_BUG_ON_MSG(bits != 64 && __builtin_constant_p(field) &&
> > + (VMCS_ENC_WIDTH(field) == VMCS_ENC_WIDTH_64BIT ||
> > + VMCS_ENC_WIDTH(field) == VMCS_ENC_WIDTH_NATURAL),
> > + "Invalid TD VMCS access for 64-bit field");
> > + BUILD_BUG_ON_MSG(bits != 32 && __builtin_constant_p(field) &&
> > + VMCS_ENC_WIDTH(field) == VMCS_ENC_WIDTH_32BIT,
> > + "Invalid TD VMCS access for 32-bit field");
> > + BUILD_BUG_ON_MSG(bits != 16 && __builtin_constant_p(field) &&
> > + VMCS_ENC_WIDTH(field) == VMCS_ENC_WIDTH_16BIT,
> > + "Invalid TD VMCS access for 16-bit field");
> > +}
> > +
> > +static __always_inline void tdvps_state_non_arch_check(u64 field, u8 bits) {}
> > +static __always_inline void tdvps_management_check(u64 field, u8 bits) {}
> > +
> > +#define TDX_BUILD_TDVPS_ACCESSORS(bits, uclass, lclass) \
> > +static __always_inline u##bits td_##lclass##_read##bits(struct vcpu_tdx *tdx, \
> > + u32 field) \
> > +{ \
> > + struct tdx_module_output out; \
> > + u64 err; \
> > + \
> > + tdvps_##lclass##_check(field, bits); \
> > + err = tdh_vp_rd(tdx->tdvpr.pa, TDVPS_##uclass(field), &out); \
> > + if (unlikely(err)) { \
> > + pr_err("TDH_VP_RD["#uclass".0x%x] failed: 0x%llx\n", \
> > + field, err); \
> > + return 0; \
> > + } \
> > + return (u##bits)out.r8; \
> > +} \
> > +static __always_inline void td_##lclass##_write##bits(struct vcpu_tdx *tdx, \
> > + u32 field, u##bits val) \
> > +{ \
> > + struct tdx_module_output out; \
> > + u64 err; \
> > + \
> > + tdvps_##lclass##_check(field, bits); \
> > + err = tdh_vp_wr(tdx->tdvpr.pa, TDVPS_##uclass(field), val, \
> > + GENMASK_ULL(bits - 1, 0), &out); \
> > + if (unlikely(err)) \
> > + pr_err("TDH_VP_WR["#uclass".0x%x] = 0x%llx failed: 0x%llx\n", \
> > + field, (u64)val, err); \
> > +} \
> > +static __always_inline void td_##lclass##_setbit##bits(struct vcpu_tdx *tdx, \
> > + u32 field, u64 bit) \
> > +{ \
> > + struct tdx_module_output out; \
> > + u64 err; \
> > + \
> > + tdvps_##lclass##_check(field, bits); \
> > + err = tdh_vp_wr(tdx->tdvpr.pa, TDVPS_##uclass(field), bit, bit, \
> > + &out); \
> > + if (unlikely(err)) \
> > + pr_err("TDH_VP_WR["#uclass".0x%x] |= 0x%llx failed: 0x%llx\n", \
> > + field, bit, err); \
> > +} \
> > +static __always_inline void td_##lclass##_clearbit##bits(struct vcpu_tdx *tdx, \
> > + u32 field, u64 bit) \
> > +{ \
> > + struct tdx_module_output out; \
> > + u64 err; \
> > + \
> > + tdvps_##lclass##_check(field, bits); \
> > + err = tdh_vp_wr(tdx->tdvpr.pa, TDVPS_##uclass(field), 0, bit, \
> > + &out); \
> > + if (unlikely(err)) \
> > + pr_err("TDH_VP_WR["#uclass".0x%x] &= ~0x%llx failed: 0x%llx\n", \
> > + field, bit, err); \
> > +}
>
> For the set of accessors, although there will be kernel errer message when
> tdh_vp_{rd,wr} fails,
> the caller doesn't know these function calls succeed or not. Won't this
> cause any unexpected
> behavior?

Oh right. Basically tdh_vp_{rd, wr} should fail as long as parameters are correct.
So I'll add KVM_BUG_ON(). TDX module takes shared lock on TDVPR, TDR and TDCS.
It should fails with TDX_OPERAND_BUSY on run time. (At least with TDX module 1.0)

Thanks,
--
Isaku Yamahata <isaku.yamahata@gmail.com>