[Devel] [PATCH RHEL7 COMMIT] ms/kvm/x86: Hyper-V SynIC message slot pending clearing at SINT ack

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.4.5.vz7.11.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.4.5.vz7.11.2
------>
commit f1144893f2055265f21f16083ee3391c4cef5849
Author: Andrey Smetanin <asmetanin at virtuozzo.com>
Date:   Tue Feb 16 13:50:22 2016 +0400

    ms/kvm/x86: Hyper-V SynIC message slot pending clearing at SINT ack
    
    The SynIC message protocol mandates that the message slot is claimed
    by atomically setting message type to something other than HVMSG_NONE.
    If another message is to be delivered while the slot is still busy,
    message pending flag is asserted to indicate to the guest that the
    hypervisor wants to be notified when the slot is released.
    
    To make sure the protocol works regardless of where the message
    sources are (kernel or userspace), clear the pending flag on SINT ACK
    notification, and let the message sources compete for the slot again.
    
    ms commit - 765eaa0f70eaa274ec8b815d8c210c20cf7b6dbc.
    
    Signed-off-by: Andrey Smetanin <asmetanin at virtuozzo.com>
    
    Reviewed-by: Roman Kagan <rkagan at virtuozzo.com>
    CC: Gleb Natapov <gleb at kernel.org>
    CC: Paolo Bonzini <pbonzini at redhat.com>
    CC: "K. Y. Srinivasan" <kys at microsoft.com>
    CC: Haiyang Zhang <haiyangz at microsoft.com>
    CC: Vitaly Kuznetsov <vkuznets at redhat.com>
    CC: Roman Kagan <rkagan at virtuozzo.com>
    CC: Denis V. Lunev <den at openvz.org>
    CC: qemu-devel at nongnu.org
    Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
---
 arch/x86/kvm/hyperv.c    | 31 +++++++++++++++++++++++++++++++
 include/linux/kvm_host.h |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 131f6b6..ab46195 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -27,6 +27,7 @@
 #include "hyperv.h"
 
 #include <linux/kvm_host.h>
+#include <linux/highmem.h>
 #include <asm/apicdef.h>
 #include <trace/events/kvm.h>
 
@@ -116,13 +117,43 @@ static struct kvm_vcpu_hv_synic *synic_get(struct kvm *kvm, u32 vcpu_id)
 	return (synic->active) ? synic : NULL;
 }
 
+static void synic_clear_sint_msg_pending(struct kvm_vcpu_hv_synic *synic,
+					u32 sint)
+{
+	struct kvm_vcpu *vcpu = synic_to_vcpu(synic);
+	struct page *page;
+	gpa_t gpa;
+	struct hv_message *msg;
+	struct hv_message_page *msg_page;
+
+	gpa = synic->msg_page & PAGE_MASK;
+	page = kvm_vcpu_gfn_to_page(vcpu, gpa >> PAGE_SHIFT);
+	if (is_error_page(page)) {
+		vcpu_err(vcpu, "Hyper-V SynIC can't get msg page, gpa 0x%llx\n",
+			 gpa);
+		return;
+	}
+	msg_page = kmap_atomic(page);
+
+	msg = &msg_page->sint_message[sint];
+	msg->header.message_flags.msg_pending = 0;
+
+	kunmap_atomic(msg_page);
+	kvm_release_page_dirty(page);
+	kvm_vcpu_mark_page_dirty(vcpu, gpa >> PAGE_SHIFT);
+}
+
 static void kvm_hv_notify_acked_sint(struct kvm_vcpu *vcpu, u32 sint)
 {
 	struct kvm *kvm = vcpu->kvm;
+	struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);
 	int gsi, idx;
 
 	vcpu_debug(vcpu, "Hyper-V SynIC acked sint %d\n", sint);
 
+	if (synic->msg_page & HV_SYNIC_SIMP_ENABLE)
+		synic_clear_sint_msg_pending(synic, sint);
+
 	idx = srcu_read_lock(&kvm->irq_srcu);
 	gsi = atomic_read(&vcpu_to_synic(vcpu)->sint_to_gsi[sint]);
 	if (gsi != -1)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b0fa329..453af61 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -439,6 +439,8 @@ struct kvm {
 
 #define vcpu_debug(vcpu, fmt, ...)					\
 	kvm_debug("vcpu%i " fmt, (vcpu)->vcpu_id, ## __VA_ARGS__)
+#define vcpu_err(vcpu, fmt, ...)					\
+	kvm_err("vcpu%i " fmt, (vcpu)->vcpu_id, ## __VA_ARGS__)
 
 static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
 {