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Message-ID: <565E23E7.5090800@zytor.com>
Date: Tue, 1 Dec 2015 14:49:11 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Sinclair Yeh <syeh@...are.com>, x86@...nel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Alok Kataria <akataria@...are.com>,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Xavier Deguillard <xdeguillard@...are.com>
Subject: Re: [PATCH 1/6] x86: Add VMWare Host Communication Macros
On 12/01/15 14:18, Sinclair Yeh wrote:
> These macros will be used by multiple VMWare modules for handling
> host communication.
> + __asm__ __volatile__ ("inl %%dx" : \
This is odd at best; the standard assembly form of this instruction is:
inl (%dx),%eax
Also, we don't need the underscored forms of asm and volatile for kernel
code.
> + __asm__ __volatile__ ("movq %13, %%rbp;" \
> + "cld; rep outsb; " \
> + "movq %%rbp, %6" : \
cld shouldn't be necessary here, DF=0 is part of the normal ABI environment.
You also don't save/restore %rbp here, but you do below? Seems very odd.
It might be better do so something like:
+#define VMW_PORT_HB_OUT(in1, in2, port_num, magic, \
+ eax, ebx, ecx, edx, si, di, bp) \
+({ \
+ __asm__ __volatile__ ("xchgq %6, %%rbp;" \
+ "cld; rep outsb; " \
+ "xchgq %%rbp, %6" : \
+ "=a"(eax), \
+ "=b"(ebx), \
+ "=c"(ecx), \
+ "=d"(edx), \
+ "+S"(si), \
+ "+D"(di), \
+ "+r"(bp) : \
+ "a"(magic), \
+ "b"(in1), \
+ "c"(in2), \
+ "d"(port_num) : \
+ "memory", "cc"); \
+})
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