linux-kernel - [PATCH 4/7] x86/hyperv: implement rep hypercalls

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Date:   Fri,  7 Apr 2017 13:26:58 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     devel@...uxdriverproject.org, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jork Loeser <Jork.Loeser@...rosoft.com>
Subject: [PATCH 4/7] x86/hyperv: implement rep hypercalls

Rep hypercalls are normal hypercalls which perform multiple actions at
once. Hyper-V guarantees to return exectution to the caller in not more
than 50us and the caller needs to use hypercall continuation. Touch NMI
watchdog between hypercall invocations.

This is going to be used for HvFlushVirtualAddressList hypercall for
remote TLB flushing.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/include/asm/mshyperv.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 9a5f58b..a2c996b 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -4,6 +4,7 @@
 #include <linux/types.h>
 #include <linux/interrupt.h>
 #include <linux/clocksource.h>
+#include <linux/nmi.h>
 #include <asm/hyperv.h>
 
 /*
@@ -253,6 +254,26 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
 #endif
 }
 
+static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, void *input,
+				      void *output)
+{
+	union hv_hypercall_input hc_input = { .code = code,
+					      .rep_count = rep_count};
+	u64 status;
+
+	do {
+		status = hv_do_hypercall(hc_input.as_uint64, input, output);
+		if ((status & 0xffff) != HV_STATUS_SUCCESS)
+			return status;
+
+		hc_input.rep_start = (status >> 32) & 0xfff;
+
+		touch_nmi_watchdog();
+	} while (hc_input.rep_start < hc_input.rep_count);
+
+	return status;
+}
+
 void hyperv_init(void);
 void hyperv_report_panic(struct pt_regs *regs);
 bool hv_is_hypercall_page_setup(void);
-- 
2.9.3