x86/paravirt: Add paravirt_{read,write}_msr()

This adds paravirt callbacks for unsafe MSR access.  On native, they
call native_{read,write}_msr().  On Xen, they use xen_{read,write}_msr_safe().

Nothing uses them yet for ease of bisection.  The next patch will
use them in rdmsrl(), wrmsrl(), etc.

I intentionally didn't make them warn on #GP on Xen.  I think that
should be done separately by the Xen maintainers.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/880eebc5dcd2ad9f310d41345f82061ea500e9fa.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 81ef2d5c2a24..97839fa8b8aa 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -130,6 +130,17 @@ static inline void wbinvd(void)
 
 #define get_kernel_rpl()  (pv_info.kernel_rpl)
 
+static inline u64 paravirt_read_msr(unsigned msr)
+{
+	return PVOP_CALL1(u64, pv_cpu_ops.read_msr, msr);
+}
+
+static inline void paravirt_write_msr(unsigned msr,
+				      unsigned low, unsigned high)
+{
+	return PVOP_VCALL3(pv_cpu_ops.write_msr, msr, low, high);
+}
+
 static inline u64 paravirt_read_msr_safe(unsigned msr, int *err)
 {
 	return PVOP_CALL2(u64, pv_cpu_ops.read_msr_safe, msr, err);