Commit c30c4b25 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Dave Hansen
Browse files

x86/tdx: Refactor __tdx_hypercall() to allow pass down more arguments 



RDI is the first argument to __tdx_hypercall() that used to pass pointer
to struct tdx_hypercall_args. RSI is the second argument that contains
flags, such as TDX_HCALL_HAS_OUTPUT and TDX_HCALL_ISSUE_STI.

RDI and RSI can also be used as arguments to TDVMCALL leafs. Move RDI to
RAX and RSI to RBP to free up them for the hypercall arguments.

RAX saved on stack during TDCALL as it returns status code in the
register.

RBP value has to be restored before returning from __tdx_hypercall() as
it is callee-saved register.

This is preparatory patch. No functional change.

Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20230126221159.8635-4-kirill.shutemov%40linux.intel.com
parent 0da908c2

arch/x86/coco/tdx/tdcall.S

+28 −18
Original line number Diff line number Diff line
@@ -124,19 +124,26 @@ SYM_FUNC_START(__tdx_hypercall) 
	push %r14

	push %r13

	push %r12

	push %rbp



	/* Free RDI and RSI to be used as TDVMCALL arguments */

	movq %rdi, %rax

	movq %rsi, %rbp



	/* Copy hypercall registers from arg struct: */

	movq TDX_HYPERCALL_r10(%rax), %r10

	movq TDX_HYPERCALL_r11(%rax), %r11

	movq TDX_HYPERCALL_r12(%rax), %r12

	movq TDX_HYPERCALL_r13(%rax), %r13

	movq TDX_HYPERCALL_r14(%rax), %r14

	movq TDX_HYPERCALL_r15(%rax), %r15



	push %rax



	/* Mangle function call ABI into TDCALL ABI: */

	/* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */

	xor %eax, %eax



	/* Copy hypercall registers from arg struct: */

	movq TDX_HYPERCALL_r10(%rdi), %r10

	movq TDX_HYPERCALL_r11(%rdi), %r11

	movq TDX_HYPERCALL_r12(%rdi), %r12

	movq TDX_HYPERCALL_r13(%rdi), %r13

	movq TDX_HYPERCALL_r14(%rdi), %r14

	movq TDX_HYPERCALL_r15(%rdi), %r15



	movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx



	/*
@@ -148,7 +155,7 @@ SYM_FUNC_START(__tdx_hypercall) 
	 * HLT operation indefinitely. Since this is the not the desired

	 * result, conditionally call STI before TDCALL.

	 */

	testq $TDX_HCALL_ISSUE_STI, %rsi

	testq $TDX_HCALL_ISSUE_STI, %rbp

	jz .Lskip_sti

	sti

.Lskip_sti:
@@ -165,20 +172,22 @@ SYM_FUNC_START(__tdx_hypercall) 
	testq %rax, %rax

	jne .Lpanic



	/* TDVMCALL leaf return code is in R10 */

	movq %r10, %rax

	pop %rax



	/* Copy hypercall result registers to arg struct if needed */

	testq $TDX_HCALL_HAS_OUTPUT, %rsi

	testq $TDX_HCALL_HAS_OUTPUT, %rbp

	jz .Lout



	movq %r10, TDX_HYPERCALL_r10(%rdi)

	movq %r11, TDX_HYPERCALL_r11(%rdi)

	movq %r12, TDX_HYPERCALL_r12(%rdi)

	movq %r13, TDX_HYPERCALL_r13(%rdi)

	movq %r14, TDX_HYPERCALL_r14(%rdi)

	movq %r15, TDX_HYPERCALL_r15(%rdi)

	movq %r10, TDX_HYPERCALL_r10(%rax)

	movq %r11, TDX_HYPERCALL_r11(%rax)

	movq %r12, TDX_HYPERCALL_r12(%rax)

	movq %r13, TDX_HYPERCALL_r13(%rax)

	movq %r14, TDX_HYPERCALL_r14(%rax)

	movq %r15, TDX_HYPERCALL_r15(%rax)

.Lout:

	/* TDVMCALL leaf return code is in R10 */

	movq %r10, %rax



	/*

	 * Zero out registers exposed to the VMM to avoid speculative execution

	 * with VMM-controlled values. This needs to include all registers
@@ -189,6 +198,7 @@ SYM_FUNC_START(__tdx_hypercall) 
	xor %r11d, %r11d



	/* Restore callee-saved GPRs as mandated by the x86_64 ABI */

	pop %rbp

	pop %r12

	pop %r13

	pop %r14