[RFC][PATCH 15/22] x86,vmx: Remove .fixup usage

Peter Zijlstra
2021-11-04T17:01:39Z

In the vmread exceptin path, use the, thus far, unused output register
to push the @fault argument onto the stack. This, in turn, enables the
exception handler to not do pushes and only modify that register when
an exception does occur.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kvm/vmx/vmx_ops.h | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

--- a/arch/x86/kvm/vmx/vmx_ops.h
+++ b/arch/x86/kvm/vmx/vmx_ops.h
@@ -80,9 +80,11 @@ static __always_inline unsigned long __v
* @field, and bounce through the trampoline to preserve
* volatile registers.
*/
- "push $0\n\t"
+ "xorl %k1, %k1\n\t"
+ "2:\n\t"
+ "push %1\n\t"
"push %2\n\t"
- "2:call vmread_error_trampoline\n\t"
+ "call vmread_error_trampoline\n\t"

/*
* Unwind the stack. Note, the trampoline zeros out the
@@ -93,12 +95,8 @@ static __always_inline unsigned long __v
"3:\n\t"

/* VMREAD faulted. As above, except push '1' for @fault. */
- ".pushsection .fixup, \"ax\"\n\t"
- "4: push $1\n\t"
- "push %2\n\t"
- "jmp 2b\n\t"
- ".popsection\n\t"
- _ASM_EXTABLE(1b, 4b)
+ _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_ONE_REG, %1)
+
: ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc");
return value;
}