Re: [PATCH v13 011/113] KVM: TDX: Add C wrapper functions for SEAMCALLs to the TDX module

[Zhi Wang <zhi.wang.linux@gmail.com>]

On Sun, 12 Mar 2023 10:55:35 -0700
isaku.yamahata@intel.com wrote:

> From: Isaku Yamahata <isaku.yamahata@intel.com>
> 
> A VMM interacts with the TDX module using a new instruction (SEAMCALL).  A
> TDX VMM uses SEAMCALLs where a VMX VMM would have directly interacted with
  ^ This sentence is little bit confusing, it can be removed. The next two sentences have stated the situation clearly.
> VMX instructions.  For instance, a TDX VMM does not have full access to the
> VM control structure corresponding to VMX VMCS.  Instead, a VMM induces the
> TDX module to act on behalf via SEAMCALLs.
> 
> Export __seamcall and define C wrapper functions for SEAMCALLs for
> readability.
> 
> Some SEAMCALL APIs donates host pages to TDX module or guest TD and the
> donated pages are encrypted.  Some of such SEAMCALLs flush cache lines
                                      ^ "some of" can be removed.
> (typically by movdir64b instruction), some don't.  Those that doesn't
> clear cache lines require the VMM to flush the cache lines to avoid cache
> line alias.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
>  arch/x86/include/asm/tdx.h       |   4 +
>  arch/x86/kvm/vmx/tdx_ops.h       | 202 +++++++++++++++++++++++++++++++
>  arch/x86/virt/vmx/tdx/seamcall.S |   2 +
>  arch/x86/virt/vmx/tdx/tdx.h      |   3 -
>  4 files changed, 208 insertions(+), 3 deletions(-)
>  create mode 100644 arch/x86/kvm/vmx/tdx_ops.h
> 
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 112a5b9bd5cd..6c01ab572c1f 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -104,10 +104,14 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
>  bool platform_tdx_enabled(void);
>  int tdx_cpu_enable(void);
>  int tdx_enable(void);
> +u64 __seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> +	       struct tdx_module_output *out);
>  #else	/* !CONFIG_INTEL_TDX_HOST */
>  static inline bool platform_tdx_enabled(void) { return false; }
>  static inline int tdx_cpu_enable(void) { return -EINVAL; }
>  static inline int tdx_enable(void)  { return -EINVAL; }
> +static inline u64 __seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> +			     struct tdx_module_output *out) { return TDX_SEAMCALL_UD; };
>  #endif	/* CONFIG_INTEL_TDX_HOST */
>  
>  #endif /* !__ASSEMBLY__ */
> diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
> new file mode 100644
> index 000000000000..70e569838e1c
> --- /dev/null
> +++ b/arch/x86/kvm/vmx/tdx_ops.h
> @@ -0,0 +1,202 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* constants/data definitions for TDX SEAMCALLs */
> +
> +#ifndef __KVM_X86_TDX_OPS_H
> +#define __KVM_X86_TDX_OPS_H
> +
> +#include <linux/compiler.h>
> +
> +#include <asm/cacheflush.h>
> +#include <asm/asm.h>
> +#include <asm/kvm_host.h>
> +
> +#include "tdx_errno.h"
> +#include "tdx_arch.h"
> +#include "x86.h"
> +
> +static inline u64 kvm_seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> +			       struct tdx_module_output *out)
> +{
> +	u64 ret;
> +
> +	ret = __seamcall(op, rcx, rdx, r8, r9, out);
> +	if (ret == TDX_SEAMCALL_UD) {
> +		/*
> +		 * TDX requires VMXON or #UD.  In the case of reboot or kexec,
> +		 * VMX is made off (VMXOFF) by kvm reboot notifier,
> +		 * kvm_reboot(), while TDs are still running.  The callers check
> +		 * the returned error and complain.  Suppress it by returning 0.
> +		 */
> +		kvm_spurious_fault();
> +		return 0;
> +	}
> +	return ret;
> +}
> +
> +static inline u64 tdh_mng_addcx(hpa_t tdr, hpa_t addr)
> +{
> +	clflush_cache_range(__va(addr), PAGE_SIZE);
> +	return kvm_seamcall(TDH_MNG_ADDCX, addr, tdr, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mem_page_add(hpa_t tdr, gpa_t gpa, hpa_t hpa, hpa_t source,
> +				   struct tdx_module_output *out)
> +{
> +	clflush_cache_range(__va(hpa), PAGE_SIZE);
> +	return kvm_seamcall(TDH_MEM_PAGE_ADD, gpa, tdr, hpa, source, out);
> +}
> +
> +static inline u64 tdh_mem_sept_add(hpa_t tdr, gpa_t gpa, int level, hpa_t page,
> +				   struct tdx_module_output *out)
> +{
> +	clflush_cache_range(__va(page), PAGE_SIZE);
> +	return kvm_seamcall(TDH_MEM_SEPT_ADD, gpa | level, tdr, page, 0, out);
> +}
> +
> +static inline u64 tdh_mem_sept_remove(hpa_t tdr, gpa_t gpa, int level,
> +				      struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MEM_SEPT_REMOVE, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_vp_addcx(hpa_t tdvpr, hpa_t addr)
> +{
> +	clflush_cache_range(__va(addr), PAGE_SIZE);
> +	return kvm_seamcall(TDH_VP_ADDCX, addr, tdvpr, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mem_page_relocate(hpa_t tdr, gpa_t gpa, hpa_t hpa,
> +					struct tdx_module_output *out)
> +{
> +	clflush_cache_range(__va(hpa), PAGE_SIZE);
> +	return kvm_seamcall(TDH_MEM_PAGE_RELOCATE, gpa, tdr, hpa, 0, out);
> +}
> +
> +static inline u64 tdh_mem_page_aug(hpa_t tdr, gpa_t gpa, hpa_t hpa,
> +				   struct tdx_module_output *out)
> +{
> +	clflush_cache_range(__va(hpa), PAGE_SIZE);
> +	return kvm_seamcall(TDH_MEM_PAGE_AUG, gpa, tdr, hpa, 0, out);
> +}
> +
> +static inline u64 tdh_mem_range_block(hpa_t tdr, gpa_t gpa, int level,
> +				      struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MEM_RANGE_BLOCK, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mng_key_config(hpa_t tdr)
> +{
> +	return kvm_seamcall(TDH_MNG_KEY_CONFIG, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_create(hpa_t tdr, int hkid)
> +{
> +	clflush_cache_range(__va(tdr), PAGE_SIZE);
> +	return kvm_seamcall(TDH_MNG_CREATE, tdr, hkid, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_vp_create(hpa_t tdr, hpa_t tdvpr)
> +{
> +	clflush_cache_range(__va(tdvpr), PAGE_SIZE);
> +	return kvm_seamcall(TDH_VP_CREATE, tdvpr, tdr, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_rd(hpa_t tdr, u64 field, struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MNG_RD, tdr, field, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mr_extend(hpa_t tdr, gpa_t gpa,
> +				struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MR_EXTEND, gpa, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mr_finalize(hpa_t tdr)
> +{
> +	return kvm_seamcall(TDH_MR_FINALIZE, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_vp_flush(hpa_t tdvpr)
> +{
> +	return kvm_seamcall(TDH_VP_FLUSH, tdvpr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_vpflushdone(hpa_t tdr)
> +{
> +	return kvm_seamcall(TDH_MNG_VPFLUSHDONE, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_key_freeid(hpa_t tdr)
> +{
> +	return kvm_seamcall(TDH_MNG_KEY_FREEID, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_init(hpa_t tdr, hpa_t td_params,
> +			       struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MNG_INIT, tdr, td_params, 0, 0, out);
> +}
> +
> +static inline u64 tdh_vp_init(hpa_t tdvpr, u64 rcx)
> +{
> +	return kvm_seamcall(TDH_VP_INIT, tdvpr, rcx, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_vp_rd(hpa_t tdvpr, u64 field,
> +			    struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_VP_RD, tdvpr, field, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mng_key_reclaimid(hpa_t tdr)
> +{
> +	return kvm_seamcall(TDH_MNG_KEY_RECLAIMID, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_phymem_page_reclaim(hpa_t page,
> +					  struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_PHYMEM_PAGE_RECLAIM, page, 0, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mem_page_remove(hpa_t tdr, gpa_t gpa, int level,
> +				      struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MEM_PAGE_REMOVE, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_sys_lp_shutdown(void)
> +{
> +	return kvm_seamcall(TDH_SYS_LP_SHUTDOWN, 0, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mem_track(hpa_t tdr)
> +{
> +	return kvm_seamcall(TDH_MEM_TRACK, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mem_range_unblock(hpa_t tdr, gpa_t gpa, int level,
> +					struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_MEM_RANGE_UNBLOCK, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_phymem_cache_wb(bool resume)
> +{
> +	return kvm_seamcall(TDH_PHYMEM_CACHE_WB, resume ? 1 : 0, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_phymem_page_wbinvd(hpa_t page)
> +{
> +	return kvm_seamcall(TDH_PHYMEM_PAGE_WBINVD, page, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_vp_wr(hpa_t tdvpr, u64 field, u64 val, u64 mask,
> +			    struct tdx_module_output *out)
> +{
> +	return kvm_seamcall(TDH_VP_WR, tdvpr, field, val, mask, out);
> +}
> +
> +#endif /* __KVM_X86_TDX_OPS_H */
> diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
> index f81be6b9c133..b90a7fe05494 100644
> --- a/arch/x86/virt/vmx/tdx/seamcall.S
> +++ b/arch/x86/virt/vmx/tdx/seamcall.S
> @@ -1,5 +1,6 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
>  #include <linux/linkage.h>
> +#include <asm/export.h>
>  #include <asm/frame.h>
>  
>  #include "tdxcall.S"
> @@ -50,3 +51,4 @@ SYM_FUNC_START(__seamcall)
>  	FRAME_END
>  	RET
>  SYM_FUNC_END(__seamcall)
> +EXPORT_SYMBOL_GPL(__seamcall)
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 48f830087e7e..4e497f202586 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -144,7 +144,4 @@ struct tdmr_info_list {
>  	int max_tdmrs;	/* How many 'tdmr_info's are allocated */
>  };
>  

> -struct tdx_module_output;
> -u64 __seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
> -	       struct tdx_module_output *out);
Better move this part to a correct place.
>  #endif