xen: fix hvm guest with kaslr enabled

A Xen HVM guest running with KASLR enabled will die rather soon today
because the shared info page mapping is using va() too early. This was
introduced by commit a5d5f328b0e2baa5ee7c119fd66324eb79eeeb66 ("xen:
allocate page for shared info page from low memory").

In order to fix this use early_memremap() to get a temporary virtual
address for shared info until va() can be used safely.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index d23531f5f17e..de503c225ae1 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -12,6 +12,7 @@
 #include <asm/setup.h>
 #include <asm/hypervisor.h>
 #include <asm/e820/api.h>
+#include <asm/early_ioremap.h>
 
 #include <asm/xen/cpuid.h>
 #include <asm/xen/hypervisor.h>
@@ -21,6 +22,8 @@
 #include "mmu.h"
 #include "smp.h"
 
+static unsigned long shared_info_pfn;
+
 void xen_hvm_init_shared_info(void)
 {
         struct xen_add_to_physmap xatp;
@@ -28,7 +31,7 @@ void xen_hvm_init_shared_info(void)
         xatp.domid = DOMID_SELF;
         xatp.idx = 0;
         xatp.space = XENMAPSPACE_shared_info;
-        xatp.gpfn = virt_to_pfn(HYPERVISOR_shared_info);
+        xatp.gpfn = shared_info_pfn;
         if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
                 BUG();
 }
@@ -51,8 +54,16 @@ static void __init reserve_shared_info(void)
              pa += PAGE_SIZE)
                 ;
 
+        shared_info_pfn = PHYS_PFN(pa);
+
         memblock_reserve(pa, PAGE_SIZE);
-        HYPERVISOR_shared_info = __va(pa);
+        HYPERVISOR_shared_info = early_memremap(pa, PAGE_SIZE);
+}
+
+static void __init xen_hvm_init_mem_mapping(void)
+{
+        early_memunmap(HYPERVISOR_shared_info, PAGE_SIZE);
+        HYPERVISOR_shared_info = __va(PFN_PHYS(shared_info_pfn));
 }
 
 static void __init init_hvm_pv_info(void)
@@ -221,5 +232,6 @@ const struct hypervisor_x86 x86_hyper_xen_hvm = {
         .init_platform          = xen_hvm_guest_init,
         .pin_vcpu               = xen_pin_vcpu,
         .x2apic_available       = xen_x2apic_para_available,
+        .init_mem_mapping       = xen_hvm_init_mem_mapping,
 };
 EXPORT_SYMBOL(x86_hyper_xen_hvm);