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x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm
Now the TDX_HYPERCALL asm is basically identical to the TDX_MODULE_CALL with both '\saved' and '\ret' enabled, with two minor things though: 1) The way to restore the structure pointer is different The TDX_HYPERCALL uses RCX as spare to restore the structure pointer, but the TDX_MODULE_CALL assumes no spare register can be used. In other words, TDX_MODULE_CALL already covers what TDX_HYPERCALL does. 2) TDX_MODULE_CALL only clears shared registers for TDH.VP.ENTER For this just need to make that code available for the non-host case. Thus, remove the TDX_HYPERCALL and reimplement the __tdx_hypercall() using the TDX_MODULE_CALL. Extend the TDX_MODULE_CALL to cover "clear shared registers" for TDG.VP.VMCALL. Introduce a new __tdcall_saved_ret() to replace the temporary __tdcall_hypercall(). The __tdcall_saved_ret() can also be used for those new TDCALLs which require more input/output registers than the basic TDCALLs do. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/all/e68a2473fb6f5bcd78b078cae7510e9d0753b3df.1692096753.git.kai.huang%40intel.com
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@ -1,7 +1,6 @@
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/* SPDX-License-Identifier: GPL-2.0 */
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#include <asm/asm-offsets.h>
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#include <asm/asm.h>
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#include <asm/frame.h>
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#include <linux/linkage.h>
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#include <linux/errno.h>
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@ -46,135 +45,19 @@ SYM_FUNC_START(__tdcall_ret)
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SYM_FUNC_END(__tdcall_ret)
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/*
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* TDX_HYPERCALL - Make hypercalls to a TDX VMM using TDVMCALL leaf of TDCALL
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* instruction
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* __tdcall_saved_ret() - Used by TDX guests to request services from the
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* TDX module (including VMM services) using TDCALL instruction, with
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* saving output registers to the 'struct tdx_module_args' used as input.
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*
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* Transforms values in function call argument struct tdx_module_args @args
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* into the TDCALL register ABI. After TDCALL operation, VMM output is saved
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* back in @args, if \ret is 1.
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*
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* Depends on the caller to pass TDG.VP.VMCALL as the TDCALL leaf, and set
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* @args::rcx to TDVMCALL_EXPOSE_REGS_MASK.
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*
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*-------------------------------------------------------------------------
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* TD VMCALL ABI:
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*-------------------------------------------------------------------------
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*
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* Input Registers:
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*
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* RAX - TDCALL instruction leaf number (0 - TDG.VP.VMCALL)
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* RCX - BITMAP which controls which part of TD Guest GPR
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* is passed as-is to the VMM and back.
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* R10 - Set 0 to indicate TDCALL follows standard TDX ABI
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* specification. Non zero value indicates vendor
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* specific ABI.
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* R11 - VMCALL sub function number
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* RBX, RDX, RDI, RSI - Used to pass VMCALL sub function specific arguments.
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* R8-R9, R12-R15 - Same as above.
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*
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* Output Registers:
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*
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* RAX - TDCALL instruction status (Not related to hypercall
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* output).
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* RBX, RDX, RDI, RSI - Hypercall sub function specific output values.
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* R8-R15 - Same as above.
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*
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*/
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.macro TDX_HYPERCALL
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FRAME_BEGIN
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/* Save callee-saved GPRs as mandated by the x86_64 ABI */
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push %r15
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push %r14
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push %r13
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push %r12
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push %rbx
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/* Move Leaf ID to RAX */
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movq %rdi, %rax
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/* Move bitmap of shared registers to RCX */
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movq TDX_MODULE_rcx(%rsi), %rcx
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/* Copy hypercall registers from arg struct: */
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movq TDX_MODULE_r8(%rsi), %r8
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movq TDX_MODULE_r9(%rsi), %r9
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movq TDX_MODULE_r10(%rsi), %r10
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movq TDX_MODULE_r11(%rsi), %r11
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movq TDX_MODULE_r12(%rsi), %r12
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movq TDX_MODULE_r13(%rsi), %r13
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movq TDX_MODULE_r14(%rsi), %r14
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movq TDX_MODULE_r15(%rsi), %r15
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movq TDX_MODULE_rdi(%rsi), %rdi
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movq TDX_MODULE_rbx(%rsi), %rbx
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movq TDX_MODULE_rdx(%rsi), %rdx
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pushq %rsi
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movq TDX_MODULE_rsi(%rsi), %rsi
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tdcall
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/*
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* Restore the pointer of the structure to save output registers.
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*
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* RCX is used as bitmap of shared registers and doesn't hold any
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* value provided by the VMM, thus it can be used as spare to
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* restore the structure pointer.
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*/
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popq %rcx
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movq %rsi, TDX_MODULE_rsi(%rcx)
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movq %rcx, %rsi
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movq %r8, TDX_MODULE_r8(%rsi)
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movq %r9, TDX_MODULE_r9(%rsi)
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movq %r10, TDX_MODULE_r10(%rsi)
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movq %r11, TDX_MODULE_r11(%rsi)
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movq %r12, TDX_MODULE_r12(%rsi)
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movq %r13, TDX_MODULE_r13(%rsi)
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movq %r14, TDX_MODULE_r14(%rsi)
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movq %r15, TDX_MODULE_r15(%rsi)
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movq %rdi, TDX_MODULE_rdi(%rsi)
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movq %rbx, TDX_MODULE_rbx(%rsi)
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movq %rdx, TDX_MODULE_rdx(%rsi)
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/*
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* Zero out registers exposed to the VMM to avoid speculative execution
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* with VMM-controlled values. This needs to include all registers
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* present in TDVMCALL_EXPOSE_REGS_MASK, except RBX, and R12-R15 which
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* will be restored.
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*/
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xor %r8d, %r8d
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xor %r9d, %r9d
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xor %r10d, %r10d
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xor %r11d, %r11d
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xor %rdi, %rdi
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xor %rsi, %rsi
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xor %rdx, %rdx
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/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
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pop %rbx
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pop %r12
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pop %r13
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pop %r14
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pop %r15
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FRAME_END
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RET
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.endm
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/*
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*
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* __tdcall_hypercall() function ABI:
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* __tdcall_saved_ret() function ABI:
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*
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* @fn (RDI) - TDCALL leaf ID, moved to RAX
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* @args (RSI) - struct tdx_module_args for input/output
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*
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* @fn and @args::rcx from the caller must be TDG_VP_VMCALL and
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* TDVMCALL_EXPOSE_REGS_MASK respectively.
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* All registers in @args are used as input/output registers.
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*
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* On successful completion, return the hypercall error code.
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*/
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SYM_FUNC_START(__tdcall_hypercall)
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TDX_HYPERCALL
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SYM_FUNC_END(__tdcall_hypercall)
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SYM_FUNC_START(__tdcall_saved_ret)
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TDX_MODULE_CALL host=0 ret=1 saved=1
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SYM_FUNC_END(__tdcall_saved_ret)
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@ -89,11 +89,11 @@ noinstr u64 __tdx_hypercall(struct tdx_hypercall_args *args)
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};
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/*
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* Failure of __tdcall_hypercall() indicates a failure of the TDVMCALL
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* Failure of __tdcall_saved_ret() indicates a failure of the TDVMCALL
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* mechanism itself and that something has gone horribly wrong with
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* the TDX module. __tdx_hypercall_failed() never returns.
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*/
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if (__tdcall_hypercall(TDG_VP_VMCALL, &margs))
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if (__tdcall_saved_ret(TDG_VP_VMCALL, &margs))
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__tdx_hypercall_failed();
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args->r8 = margs.r8;
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@ -83,6 +83,7 @@ struct tdx_module_args {
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/* Used to communicate with the TDX module */
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u64 __tdcall(u64 fn, struct tdx_module_args *args);
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u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
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u64 __tdcall_saved_ret(u64 fn, struct tdx_module_args *args);
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/*
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* Used in __tdx_hypercall() to pass down and get back registers' values of
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};
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/* Used to request services from the VMM */
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u64 __tdcall_hypercall(u64 fn, struct tdx_module_args *args);
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u64 __tdx_hypercall(struct tdx_hypercall_args *args);
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/*
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@ -142,10 +142,10 @@
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movq %r11, TDX_MODULE_r11(%rsi)
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.endif /* \ret */
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.if \host && \saved && \ret
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.if \saved && \ret
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/*
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* Clear registers shared by guest for VP.ENTER to prevent
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* speculative use of guest's values, including those are
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* Clear registers shared by guest for VP.VMCALL/VP.ENTER to prevent
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* speculative use of guest's/VMM's values, including those are
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* restored from the stack.
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*
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* See arch/x86/kvm/vmx/vmenter.S:
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@ -170,7 +170,7 @@
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xorl %r15d, %r15d
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xorl %ebx, %ebx
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xorl %edi, %edi
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.endif /* \host && \ret && \host */
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.endif /* \ret && \host */
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.if \host
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.Lout\@:
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