Hyper-V uses a technique called overlay page for its hypercall page. It
will insert a backing page to the guest when the hypercall functionality
is enabled. That means we can use a page that is not backed by real
memory for hypercall page.
Use the top-most addressable page for that purpose. Adjust e820 code
accordingly.
We also need to register Xen's guest OS ID to Hyper-V. Use 0x3 as the
vendor ID. Fix the comment in hyperv-tlfs.h while at it.
Signed-off-by: Wei Liu <li...@microsoft.com>
---
v5:
1. use hypervisor_reserve_top_pages
2. add a macro for hypercall page mfn
3. address other misc comments
v4:
1. Use fixmap
2. Follow routines listed in TLFS
---
xen/arch/x86/e820.c | 5 +++
xen/arch/x86/guest/hyperv/hyperv.c | 57 +++++++++++++++++++++++--
xen/include/asm-x86/guest/hyperv-tlfs.h | 5 ++-
xen/include/asm-x86/guest/hyperv.h | 3 ++
4 files changed, 65 insertions(+), 5 deletions(-)
diff --git a/xen/arch/x86/e820.c b/xen/arch/x86/e820.c
index 3892c9cfb7..99643f3ea0 100644
--- a/xen/arch/x86/e820.c
+++ b/xen/arch/x86/e820.c
@@ -343,6 +343,7 @@ static unsigned long __init find_max_pfn(void)
{
unsigned int i;
unsigned long max_pfn = 0;
+ unsigned long top_pfn = ((1ull << paddr_bits) - 1) >> PAGE_SHIFT;
for (i = 0; i < e820.nr_map; i++) {
unsigned long start, end;
@@ -357,6 +358,10 @@ static unsigned long __init find_max_pfn(void)
max_pfn = end;
}
+ top_pfn -= hypervisor_reserve_top_pages();
+ if ( max_pfn >= top_pfn )
+ max_pfn = top_pfn;
+
return max_pfn;
}
diff --git a/xen/arch/x86/guest/hyperv/hyperv.c
b/xen/arch/x86/guest/hyperv/hyperv.c
index 8d38313d7a..2bedcc438c 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -19,15 +19,26 @@
* Copyright (c) 2019 Microsoft.
*/
#include <xen/init.h>
+#include <xen/version.h>
+#include <asm/fixmap.h>
#include <asm/guest.h>
#include <asm/guest/hyperv-tlfs.h>
+#include <asm/processor.h>
struct ms_hyperv_info __read_mostly ms_hyperv;
-static const struct hypervisor_ops ops = {
- .name = "Hyper-V",
-};
+static uint64_t generate_guest_id(void)
+{
+ uint64_t id;
+
+ id = (uint64_t)HV_XEN_VENDOR_ID << 48;
+ id |= (xen_major_version() << 16) | xen_minor_version();
+
+ return id;
+}
+
+static const struct hypervisor_ops ops;
const struct hypervisor_ops *__init hyperv_probe(void)
{
@@ -72,6 +83,46 @@ const struct hypervisor_ops *__init hyperv_probe(void)
return &ops;
}
+static void __init setup_hypercall_page(void)
+{
+ union hv_x64_msr_hypercall_contents hypercall_msr;
+ union hv_guest_os_id guest_id;
+ unsigned long mfn;
+
+ rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id.raw);
+ if ( !guest_id.raw )
+ {
+ guest_id.raw = generate_guest_id();
+ wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id.raw);
+ }
+
+ rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+ if ( !hypercall_msr.enable )
+ {
+ mfn = HV_HCALL_MFN;
+ hypercall_msr.enable = 1;
+ hypercall_msr.guest_physical_address = mfn;
+ wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+ } else {
+ mfn = hypercall_msr.guest_physical_address;
+ }
+
+ rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+ BUG_ON(!hypercall_msr.enable);
+
+ set_fixmap_x(FIX_X_HYPERV_HCALL, mfn << PAGE_SHIFT);
+}
+
+static void __init setup(void)
+{
+ setup_hypercall_page();
+}
+
+static const struct hypervisor_ops ops = {
+ .name = "Hyper-V",
+ .setup = setup,
+};
+
/*
* Local variables:
* mode: C
diff --git a/xen/include/asm-x86/guest/hyperv-tlfs.h
b/xen/include/asm-x86/guest/hyperv-tlfs.h
index 05c4044976..07db57b55f 100644
--- a/xen/include/asm-x86/guest/hyperv-tlfs.h
+++ b/xen/include/asm-x86/guest/hyperv-tlfs.h
@@ -318,15 +318,16 @@ struct ms_hyperv_tsc_page {
*
* Bit(s)
* 63 - Indicates if the OS is Open Source or not; 1 is Open Source
- * 62:56 - Os Type; Linux is 0x100
+ * 62:56 - Os Type; Linux 0x1, FreeBSD 0x2, Xen 0x3
* 55:48 - Distro specific identification
- * 47:16 - Linux kernel version number
+ * 47:16 - Guest OS version number
* 15:0 - Distro specific identification
*
*
*/
#define HV_LINUX_VENDOR_ID 0x8100
+#define HV_XEN_VENDOR_ID 0x8300
union hv_guest_os_id
{
uint64_t raw;
diff --git a/xen/include/asm-x86/guest/hyperv.h
b/xen/include/asm-x86/guest/hyperv.h
index c7a7f32bd5..0dcd8082ad 100644
--- a/xen/include/asm-x86/guest/hyperv.h
+++ b/xen/include/asm-x86/guest/hyperv.h
@@ -21,6 +21,9 @@
#include <xen/types.h>
+/* Use top-most MFN for hypercall page */
+#define HV_HCALL_MFN (((1ull << paddr_bits) - 1) >> HV_HYP_PAGE_SHIFT)
+
/*
* The specification says: "The partition reference time is computed
* by the following formula:
--
2.20.1
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