On 9/23/2020 3:41 AM, Borislav Petkov wrote:
Subject: Re: [PATCH v4 1/5] x86/asm: move the raw asm in iosubmit_cmds512() to special_insns.h
Start patch name with a capital letter: "Move the asm definition.."
Also, calling stuff "raw" and "core" is misleading in the kernel context
- you wanna say simply: "Carve out a generic movdir64b() helper... "
Ok I will update
On Thu, Sep 17, 2020 at 02:15:16PM -0700, Dave Jiang wrote:
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 59a3e13204c3..7bc8e714f37e 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -234,6 +234,23 @@ static inline void clwb(volatile void *__p)
#define nop() asm volatile ("nop")
+static inline void movdir64b(void *__dst, const void *src)
Make __dst be the function local variable name and keep "dst", i.e.,
without the underscores, the function parameter name.
Ok will fix
+ /*
+ * Note that this isn't an "on-stack copy", just definition of "dst"
+ * as a pointer to 64-bytes of stuff that is going to be overwritten.
+ * In the MOVDIR64B case that may be needed as you can use the
+ * MOVDIR64B instruction to copy arbitrary memory around. This trick
+ * lets the compiler know how much gets clobbered.
+ */
+ volatile struct { char _[64]; } *dst = __dst;
+
+ /* MOVDIR64B [rdx], rax */
+ asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
+ : "=m" (dst)
+ : "d" (src), "a" (dst));
+}
+
#endif /* __KERNEL__ */
#endif /* _ASM_X86_SPECIAL_INSNS_H */
