KVM guest: fix bogus wallclock physical address calculation

The use of __pa() to calculate the address of a C-visible symbol
is wrong, and can lead to unpredictable results. See arch/x86/include/asm/page.h
for details.

It should be replaced with __pa_symbol(), that does the correct math here,
by taking relocations into account.  This ensures the correct wallclock data
structure physical address is passed to the hypervisor.

Cc: stable@kernel.org
Signed-off-by: Glauber Costa <glommer@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 223af43..e5efcdc 100644 (file)
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -50,8 +50,8 @@ static unsigned long kvm_get_wallclock(void)
        struct timespec ts;
        int low, high;
 
-       low = (int)__pa(&wall_clock);
-       high = ((u64)__pa(&wall_clock) >> 32);
+       low = (int)__pa_symbol(&wall_clock);
+       high = ((u64)__pa_symbol(&wall_clock) >> 32);
        native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
 
        vcpu_time = &get_cpu_var(hv_clock);