[xen staging] x86/hyperv: skeleton for L0 assisted TLB flush

[patchbot@xxxxxxx]

commit 75550b5fa5a8fa068e35e819d8ba25e0240b20a0
Author:     Wei Liu <wl@xxxxxxx>
AuthorDate: Thu Apr 9 18:41:03 2020 +0100
Commit:     Wei Liu <wl@xxxxxxx>
CommitDate: Wed Apr 29 10:32:29 2020 +0100

    x86/hyperv: skeleton for L0 assisted TLB flush
    
    Implement a basic hook for L0 assisted TLB flush. The hook needs to
    check if prerequisites are met. If they are not met, it returns an error
    number to fall back to native flushes.
    
    Introduce a new variable to indicate if hypercall page is ready.
    
    Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
 xen/arch/x86/guest/hyperv/Makefile  |  1 +
 xen/arch/x86/guest/hyperv/hyperv.c  | 17 +++++++++++++++
 xen/arch/x86/guest/hyperv/private.h |  4 ++++
 xen/arch/x86/guest/hyperv/tlb.c     | 41 +++++++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+)

diff --git a/xen/arch/x86/guest/hyperv/Makefile 
b/xen/arch/x86/guest/hyperv/Makefile
index 68170109a9..18902c33e9 100644
--- a/xen/arch/x86/guest/hyperv/Makefile
+++ b/xen/arch/x86/guest/hyperv/Makefile
@@ -1 +1,2 @@
 obj-y += hyperv.o
+obj-y += tlb.o
diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
b/xen/arch/x86/guest/hyperv/hyperv.c
index 5ad16cf0fe..91a6782cd9 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -33,6 +33,8 @@ DEFINE_PER_CPU_READ_MOSTLY(void *, hv_input_page);
 DEFINE_PER_CPU_READ_MOSTLY(void *, hv_vp_assist);
 DEFINE_PER_CPU_READ_MOSTLY(unsigned int, hv_vp_index);
 
+static bool __read_mostly hcall_page_ready;
+
 static uint64_t generate_guest_id(void)
 {
     union hv_guest_os_id id = {};
@@ -119,6 +121,8 @@ static void __init setup_hypercall_page(void)
     BUG_ON(!hypercall_msr.enable);
 
     set_fixmap_x(FIX_X_HYPERV_HCALL, mfn << PAGE_SHIFT);
+
+    hcall_page_ready = true;
 }
 
 static int setup_hypercall_pcpu_arg(void)
@@ -199,11 +203,24 @@ static void __init e820_fixup(struct e820map *e820)
         panic("Unable to reserve Hyper-V hypercall range\n");
 }
 
+static int flush_tlb(const cpumask_t *mask, const void *va,
+                     unsigned int flags)
+{
+    if ( !(ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED) )
+        return -EOPNOTSUPP;
+
+    if ( !hcall_page_ready || !this_cpu(hv_input_page) )
+        return -ENXIO;
+
+    return hyperv_flush_tlb(mask, va, flags);
+}
+
 static const struct hypervisor_ops __initconstrel ops = {
     .name = "Hyper-V",
     .setup = setup,
     .ap_setup = ap_setup,
     .e820_fixup = e820_fixup,
+    .flush_tlb = flush_tlb,
 };
 
 /*
diff --git a/xen/arch/x86/guest/hyperv/private.h 
b/xen/arch/x86/guest/hyperv/private.h
index 956eff831f..509bedaafa 100644
--- a/xen/arch/x86/guest/hyperv/private.h
+++ b/xen/arch/x86/guest/hyperv/private.h
@@ -22,10 +22,14 @@
 #ifndef __XEN_HYPERV_PRIVIATE_H__
 #define __XEN_HYPERV_PRIVIATE_H__
 
+#include <xen/cpumask.h>
 #include <xen/percpu.h>
 
 DECLARE_PER_CPU(void *, hv_input_page);
 DECLARE_PER_CPU(void *, hv_vp_assist);
 DECLARE_PER_CPU(unsigned int, hv_vp_index);
 
+int hyperv_flush_tlb(const cpumask_t *mask, const void *va,
+                     unsigned int flags);
+
 #endif /* __XEN_HYPERV_PRIVIATE_H__  */
diff --git a/xen/arch/x86/guest/hyperv/tlb.c b/xen/arch/x86/guest/hyperv/tlb.c
new file mode 100644
index 0000000000..48f527229e
--- /dev/null
+++ b/xen/arch/x86/guest/hyperv/tlb.c
@@ -0,0 +1,41 @@
+/******************************************************************************
+ * arch/x86/guest/hyperv/tlb.c
+ *
+ * Support for TLB management using hypercalls
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (c) 2020 Microsoft.
+ */
+
+#include <xen/cpumask.h>
+#include <xen/errno.h>
+
+#include "private.h"
+
+int hyperv_flush_tlb(const cpumask_t *mask, const void *va,
+                     unsigned int flags)
+{
+    return -EOPNOTSUPP;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
--
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