x86/hyperv: handling hypercall page setup for root

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>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20210203150435.27941-8-wei.liu@kernel.org

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 612c555fb9aa7411f5c87c16d27e643d351f7024..aeea8fbf3c2378c9a301fe655b100e81f5fc3d53 100644 (file)
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -27,6 +27,7 @@
 #include <linux/cpuhotplug.h>
 #include <linux/syscore_ops.h>
 #include <clocksource/hyperv_timer.h>
+#include <linux/highmem.h>
 
 int hyperv_init_cpuhp;
 u64 hv_current_partition_id = ~0ull;
@@ -286,6 +287,9 @@ 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
@@ -454,8 +458,35 @@ 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);
+       }
 
        /*
         * hyperv_init() is called before LAPIC is initialized: see
@@ -604,7 +635,7 @@ 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);