Re: [PATCH v17 011/116] KVM: TDX: Add C wrapper functions for SEAMCALLs to the TDX module

[Binbin Wu <binbin.wu@linux.intel.com>]

On 11/7/2023 10:55 PM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> A VMM interacts with the TDX module using a new instruction (SEAMCALL).
> 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 donate host pages to TDX module or guest TD, and the
> donated pages are encrypted.  Those 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>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

>
> ---
> v15 -> v16:
> - use struct tdx_module_args instead of struct tdx_module_output
> - Add tdh_mem_sept_rd() for SEPT_VE_DISABLE=1.
> ---
>   arch/x86/include/asm/asm-prototypes.h |   1 +
>   arch/x86/include/asm/tdx.h            |  12 ++
>   arch/x86/kvm/vmx/tdx_ops.h            | 226 ++++++++++++++++++++++++++
>   arch/x86/virt/vmx/tdx/seamcall.S      |   4 +
>   4 files changed, 243 insertions(+)
>   create mode 100644 arch/x86/kvm/vmx/tdx_ops.h
>
> diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm/asm-prototypes.h
> index b1a98fa38828..1a8feb440252 100644
> --- a/arch/x86/include/asm/asm-prototypes.h
> +++ b/arch/x86/include/asm/asm-prototypes.h
> @@ -6,6 +6,7 @@
>   #include <asm/page.h>
>   #include <asm/checksum.h>
>   #include <asm/mce.h>
> +#include <asm/tdx.h>
>   
>   #include <asm-generic/asm-prototypes.h>
>   
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index b2d9d569818e..b7cfdf084860 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -115,6 +115,18 @@ int tdx_enable(void);
>   void tdx_reset_memory(void);
>   bool tdx_is_private_mem(unsigned long phys);
>   #else
> +static inline u64 __seamcall(u64 fn, struct tdx_module_args *args)
> +{
> +	return TDX_SEAMCALL_UD;
> +}
> +static inline u64 __seamcall_ret(u64 fn, struct tdx_module_args *args)
> +{
> +	return TDX_SEAMCALL_UD;
> +}
> +static inline u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args)
> +{
> +	return TDX_SEAMCALL_UD;
> +}
>   static inline bool platform_tdx_enabled(void) { return false; }
>   static inline int tdx_cpu_enable(void) { return -ENODEV; }
>   static inline int tdx_enable(void)  { return -ENODEV; }
> diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
> new file mode 100644
> index 000000000000..12fd6b8d49e0
> --- /dev/null
> +++ b/arch/x86/kvm/vmx/tdx_ops.h
> @@ -0,0 +1,226 @@
> +/* 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 tdx_seamcall(u64 op, u64 rcx, u64 rdx, u64 r8, u64 r9,
> +			       struct tdx_module_args *out)
> +{
> +	u64 ret;
> +
> +	if (out) {
> +		*out = (struct tdx_module_args) {
> +			.rcx = rcx,
> +			.rdx = rdx,
> +			.r8 = r8,
> +			.r9 = r9,
> +		};
> +		ret = __seamcall_ret(op, out);
> +	} else {
> +		struct tdx_module_args args = {
> +			.rcx = rcx,
> +			.rdx = rdx,
> +			.r8 = r8,
> +			.r9 = r9,
> +		};
> +		ret = __seamcall(op, &args);
> +	}
> +	if (unlikely(ret == TDX_SEAMCALL_UD)) {
> +		/*
> +		 * SEAMCALLs fail with TDX_SEAMCALL_UD returned when VMX is off.
> +		 * This can happen when the host gets rebooted or live
> +		 * updated. In this case, the instruction execution is ignored
> +		 * as KVM is shut down, so the error code is suppressed. Other
> +		 * than this, the error is unexpected and the execution can't
> +		 * continue as the TDX features reply on VMX to be on.
> +		 */
> +		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 tdx_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_args *out)
> +{
> +	clflush_cache_range(__va(hpa), PAGE_SIZE);
> +	return tdx_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_args *out)
> +{
> +	clflush_cache_range(__va(page), PAGE_SIZE);
> +	return tdx_seamcall(TDH_MEM_SEPT_ADD, gpa | level, tdr, page, 0, out);
> +}
> +
> +static inline u64 tdh_mem_sept_rd(hpa_t tdr, gpa_t gpa, int level,
> +				  struct tdx_module_args *out)
> +{
> +	return tdx_seamcall(TDH_MEM_SEPT_RD, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mem_sept_remove(hpa_t tdr, gpa_t gpa, int level,
> +				      struct tdx_module_args *out)
> +{
> +	return tdx_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 tdx_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_args *out)
> +{
> +	clflush_cache_range(__va(hpa), PAGE_SIZE);
> +	return tdx_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_args *out)
> +{
> +	clflush_cache_range(__va(hpa), PAGE_SIZE);
> +	return tdx_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_args *out)
> +{
> +	return tdx_seamcall(TDH_MEM_RANGE_BLOCK, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mng_key_config(hpa_t tdr)
> +{
> +	return tdx_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 tdx_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 tdx_seamcall(TDH_VP_CREATE, tdvpr, tdr, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_rd(hpa_t tdr, u64 field, struct tdx_module_args *out)
> +{
> +	return tdx_seamcall(TDH_MNG_RD, tdr, field, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mr_extend(hpa_t tdr, gpa_t gpa,
> +				struct tdx_module_args *out)
> +{
> +	return tdx_seamcall(TDH_MR_EXTEND, gpa, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mr_finalize(hpa_t tdr)
> +{
> +	return tdx_seamcall(TDH_MR_FINALIZE, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_vp_flush(hpa_t tdvpr)
> +{
> +	return tdx_seamcall(TDH_VP_FLUSH, tdvpr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_vpflushdone(hpa_t tdr)
> +{
> +	return tdx_seamcall(TDH_MNG_VPFLUSHDONE, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mng_key_freeid(hpa_t tdr)
> +{
> +	return tdx_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_args *out)
> +{
> +	return tdx_seamcall(TDH_MNG_INIT, tdr, td_params, 0, 0, out);
> +}
> +
> +static inline u64 tdh_vp_init(hpa_t tdvpr, u64 rcx)
> +{
> +	return tdx_seamcall(TDH_VP_INIT, tdvpr, rcx, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_vp_rd(hpa_t tdvpr, u64 field,
> +			    struct tdx_module_args *out)
> +{
> +	return tdx_seamcall(TDH_VP_RD, tdvpr, field, 0, 0, out);
> +}
> +
> +static inline u64 tdh_mng_key_reclaimid(hpa_t tdr)
> +{
> +	return tdx_seamcall(TDH_MNG_KEY_RECLAIMID, tdr, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_phymem_page_reclaim(hpa_t page,
> +					  struct tdx_module_args *out)
> +{
> +	return tdx_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_args *out)
> +{
> +	return tdx_seamcall(TDH_MEM_PAGE_REMOVE, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_sys_lp_shutdown(void)
> +{
> +	return tdx_seamcall(TDH_SYS_LP_SHUTDOWN, 0, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_mem_track(hpa_t tdr)
> +{
> +	return tdx_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_args *out)
> +{
> +	return tdx_seamcall(TDH_MEM_RANGE_UNBLOCK, gpa | level, tdr, 0, 0, out);
> +}
> +
> +static inline u64 tdh_phymem_cache_wb(bool resume)
> +{
> +	return tdx_seamcall(TDH_PHYMEM_CACHE_WB, resume ? 1 : 0, 0, 0, 0, NULL);
> +}
> +
> +static inline u64 tdh_phymem_page_wbinvd(hpa_t page)
> +{
> +	return tdx_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_args *out)
> +{
> +	return tdx_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 5b1f2286aea9..73042f7f23be 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"
> @@ -21,6 +22,7 @@
>   SYM_FUNC_START(__seamcall)
>   	TDX_MODULE_CALL host=1
>   SYM_FUNC_END(__seamcall)
> +EXPORT_SYMBOL_GPL(__seamcall)
>   
>   /*
>    * __seamcall_ret() - Host-side interface functions to SEAM software
> @@ -40,6 +42,7 @@ SYM_FUNC_END(__seamcall)
>   SYM_FUNC_START(__seamcall_ret)
>   	TDX_MODULE_CALL host=1 ret=1
>   SYM_FUNC_END(__seamcall_ret)
> +EXPORT_SYMBOL_GPL(__seamcall_ret)
>   
>   /*
>    * __seamcall_saved_ret() - Host-side interface functions to SEAM software
> @@ -59,3 +62,4 @@ SYM_FUNC_END(__seamcall_ret)
>   SYM_FUNC_START(__seamcall_saved_ret)
>   	TDX_MODULE_CALL host=1 ret=1 saved=1
>   SYM_FUNC_END(__seamcall_saved_ret)
> +EXPORT_SYMBOL_GPL(__seamcall_saved_ret)