linux-kernel - [tip:x86/platform] x86/hyper-v: Introduce fast hypercall implementation

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Date:   Thu, 10 Aug 2017 09:37:56 -0700
From:   tip-bot for Vitaly Kuznetsov <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, andy.shevchenko@...il.com,
        Jork.Loeser@...rosoft.com, sixiao@...rosoft.com,
        haiyangz@...rosoft.com, vkuznets@...hat.com, kys@...rosoft.com,
        mingo@...nel.org, sthemmin@...rosoft.com, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, luto@...nel.org,
        torvalds@...ux-foundation.org, hpa@...or.com
Subject: [tip:x86/platform] x86/hyper-v: Introduce fast hypercall
 implementation

Commit-ID:  6a8edbd0c54ae266b12f4f63e406313481c9d4bc
Gitweb:     http://git.kernel.org/tip/6a8edbd0c54ae266b12f4f63e406313481c9d4bc
Author:     Vitaly Kuznetsov <vkuznets@...hat.com>
AuthorDate: Wed, 2 Aug 2017 18:09:15 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 16:50:22 +0200

x86/hyper-v: Introduce fast hypercall implementation

Hyper-V supports 'fast' hypercalls when all parameters are passed through
registers. Implement an inline version of a simpliest of these calls:
hypercall with one 8-byte input and no output.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Reviewed-by: Stephen Hemminger <sthemmin@...rosoft.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: Jork Loeser <Jork.Loeser@...rosoft.com>
Cc: K. Y. Srinivasan <kys@...rosoft.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Simon Xiao <sixiao@...rosoft.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: devel@...uxdriverproject.org
Link: http://lkml.kernel.org/r/20170802160921.21791-4-vkuznets@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/mshyperv.h | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 6fa5e34..e484255 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -209,6 +209,40 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
 	return hv_status;
 }
 
+#define HV_HYPERCALL_FAST_BIT		BIT(16)
+
+/* Fast hypercall with 8 bytes of input and no output */
+static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
+{
+	u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
+	register void *__sp asm(_ASM_SP);
+
+#ifdef CONFIG_X86_64
+	{
+		__asm__ __volatile__("call *%4"
+				     : "=a" (hv_status), "+r" (__sp),
+				       "+c" (control), "+d" (input1)
+				     : "m" (hv_hypercall_pg)
+				     : "cc", "r8", "r9", "r10", "r11");
+	}
+#else
+	{
+		u32 input1_hi = upper_32_bits(input1);
+		u32 input1_lo = lower_32_bits(input1);
+
+		__asm__ __volatile__ ("call *%5"
+				      : "=A"(hv_status),
+					"+c"(input1_lo),
+					"+r"(__sp)
+				      :	"A" (control),
+					"b" (input1_hi),
+					"m" (hv_hypercall_pg)
+				      : "cc", "edi", "esi");
+	}
+#endif
+		return hv_status;
+}
+
 void hyperv_init(void);
 void hyperv_report_panic(struct pt_regs *regs);
 bool hv_is_hypercall_page_setup(void);