Re: [PATCH 2/4] x86/vmware: Add a header file for hypercall definitions

From: Thomas HellstrÃm (VMware)
Date: Tue Aug 20 2019 - 15:19:48 EST

On 8/20/19 3:42 PM, Thomas Gleixner wrote:
On Tue, 20 Aug 2019, Thomas HellstrÃm (VMware) wrote:

On 8/20/19 1:32 PM, Peter Zijlstra wrote:
On Sun, Aug 18, 2019 at 04:33:14PM +0200, Thomas HellstrÃm (VMware) wrote:

+ ALTERNATIVE_2(".byte 0xed", \
+ ".byte 0x0f, 0x01, 0xc1", X86_FEATURE_VMW_VMCALL, \
+ ".byte 0x0f, 0x01, 0xd9", X86_FEATURE_VMW_VMMCALL)
For sanity, could we either add comments, or macros for those
Hmm. Here I followed and slightly extended what was done in asm/kvm_para.h.

What confuses me a bit is, if it's clarity we're after, why don't people use

ALTERNATIVE_2("inl (%%dx)", \
"vmcall", X86_FEATURE_VMW_VMCALL, \

Seems to build fine here. Is it fear of old assemblers not supporting, for
example vmmcall
The requirement for binutils is version >= 2.21. If 2.21 supports vmcall and
vmmcall all good.



So I tested 2.20.1 and 2.21.1 from, and both seem to assemble (as-new) and disassemble (objdump -S) vmcall and vmmcall fine so I think we should be OK using the mnemonic format then.