[PATCH v3 08/17] x86/hyperv: handling hypercall page setup for root

Wei Liu
2020-11-24T17:08:16Z

When Linux is running as the root partition, the hypercall page will
have already been setup by Hyper-V. Copy the content over to the
allocated page.

Add checks to hv_suspend & co to bail early because they are not
supported in this setup yet.

Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Co-Developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
Co-Developed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Co-Developed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
---
v3:
1. Use HV_HYP_PAGE_SIZE.
2. Add checks to hv_suspend & co.
---
arch/x86/hyperv/hv_init.c | 37 ++++++++++++++++++++++++++++++++++---
1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index fc9941bd8653..ad8e77859b32 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -25,6 +25,7 @@
#include <linux/cpuhotplug.h>
#include <linux/syscore_ops.h>
#include <clocksource/hyperv_timer.h>
+#include <linux/highmem.h>

u64 hv_current_partition_id = ~0ull;
EXPORT_SYMBOL_GPL(hv_current_partition_id);
@@ -283,6 +284,9 @@ static int hv_suspend(void)
union hv_x64_msr_hypercall_contents hypercall_msr;
int ret;

+ if (hv_root_partition)
+ return -EPERM;
+
/*
* Reset the hypercall page as it is going to be invalidated
* accross hibernation. Setting hv_hypercall_pg to NULL ensures
@@ -433,8 +437,35 @@ void __init hyperv_init(void)

rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
hypercall_msr.enable = 1;
- hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
- wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+ if (hv_root_partition) {
+ struct page *pg;
+ void *src, *dst;
+
+ /*
+ * For the root partition, the hypervisor will set up its
+ * hypercall page. The hypervisor guarantees it will not show
+ * up in the root's address space. The root can't change the
+ * location of the hypercall page.
+ *
+ * Order is important here. We must enable the hypercall page
+ * so it is populated with code, then copy the code to an
+ * executable page.
+ */
+ wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+ pg = vmalloc_to_page(hv_hypercall_pg);
+ dst = kmap(pg);
+ src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE,
+ MEMREMAP_WB);
+ BUG_ON(!(src && dst));
+ memcpy(dst, src, HV_HYP_PAGE_SIZE);
+ memunmap(src);
+ kunmap(pg);
+ } else {
+ hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
+ wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+ }

/*
* Ignore any errors in setting up stimer clockevents
@@ -577,6 +608,6 @@ EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);

bool hv_is_hibernation_supported(void)
{
- return acpi_sleep_state_supported(ACPI_STATE_S4);
+ return !hv_root_partition && acpi_sleep_state_supported(ACPI_STATE_S4);
}
EXPORT_SYMBOL_GPL(hv_is_hibernation_supported);
--
2.20.1