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

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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: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20230126221159.8635-4-kirill.shutemov%40linux.intel.com
This commit is contained in:
Kirill A. Shutemov 2023-01-27 01:11:55 +03:00 • committed by Dave Hansen
parent 0da908c291
commit c30c4b2555
1 changed files with 30 additions and 20 deletions
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50
arch/x86/coco/tdx/tdcall.S
View file

@ -124,19 +124,26 @@ SYM_FUNC_START(__tdx_hypercall)
push %r14 push %r14
push %r13 push %r13
push %r12 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: */ /* Mangle function call ABI into TDCALL ABI: */
/* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */ /* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */
xor %eax, %eax 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 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 * HLT operation indefinitely. Since this is the not the desired
* result, conditionally call STI before TDCALL. * result, conditionally call STI before TDCALL.
*/ */
testq $TDX_HCALL_ISSUE_STI, %rsi testq $TDX_HCALL_ISSUE_STI, %rbp
jz .Lskip_sti jz .Lskip_sti
sti sti
.Lskip_sti: .Lskip_sti:
@ -165,20 +172,22 @@ SYM_FUNC_START(__tdx_hypercall)
testq %rax, %rax testq %rax, %rax
jne .Lpanic jne .Lpanic
pop %rax
/* Copy hypercall result registers to arg struct if needed */
testq $TDX_HCALL_HAS_OUTPUT, %rbp
jz .Lout
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 */ /* TDVMCALL leaf return code is in R10 */
movq %r10, %rax movq %r10, %rax
/* Copy hypercall result registers to arg struct if needed */
testq $TDX_HCALL_HAS_OUTPUT, %rsi
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)
.Lout:
/* /*
* Zero out registers exposed to the VMM to avoid speculative execution * Zero out registers exposed to the VMM to avoid speculative execution
* with VMM-controlled values. This needs to include all registers * with VMM-controlled values. This needs to include all registers
@ -189,6 +198,7 @@ SYM_FUNC_START(__tdx_hypercall)
xor %r11d, %r11d xor %r11d, %r11d
/* Restore callee-saved GPRs as mandated by the x86_64 ABI */ /* Restore callee-saved GPRs as mandated by the x86_64 ABI */
pop %rbp
pop %r12 pop %r12
pop %r13 pop %r13
pop %r14 pop %r14