KVM: x86: add tracepoints around __direct_map and FNAME(fetch)

These are useful in debugging shadow paging.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

CVE-2018-12207

(backported from commit 335e192a)
[tyhicks: Backport to 4.4
 - Continue to use pfn_t instead of kvm_pfn_t
 - Remove the use of shadow_present_mask in the kvm_mmu_set_spte trace
   point since we don't have commit ffb128c8 ("kvm: mmu: don't set
   the present bit unconditionally")
 - Open code is_executable_pte() in the kvm_mmu_set_spte() trace point
   since that function doesn't exit]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kvm/mmu.c

@@ -129,9 +129,6 @@ module_param(dbg, bool, 0644);
 
 #include <trace/events/kvm.h>
 
-#define CREATE_TRACE_POINTS
-#include "mmutrace.h"
-
 #define SPTE_HOST_WRITEABLE	(1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
 #define SPTE_MMU_WRITEABLE	(1ULL << (PT_FIRST_AVAIL_BITS_SHIFT + 1))
 
@@ -192,6 +189,10 @@ static u64 __read_mostly shadow_mmio_mask;
 static void mmu_spte_set(u64 *sptep, u64 spte);
 static void mmu_free_roots(struct kvm_vcpu *vcpu);
 
+#define CREATE_TRACE_POINTS
+#include "mmutrace.h"
+
+
 void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask)
 {
 	shadow_mmio_mask = mmio_mask;
@@ -2635,10 +2636,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
 		ret = RET_PF_EMULATE;
 
 	pgprintk("%s: setting spte %llx\n", __func__, *sptep);
-	pgprintk("instantiating %s PTE (%s) at %llx (%llx) addr %p\n",
-		 is_large_pte(*sptep)? "2MB" : "4kB",
-		 *sptep & PT_PRESENT_MASK ?"RW":"R", gfn,
-		 *sptep, sptep);
+	trace_kvm_mmu_set_spte(level, gfn, sptep);
 	if (!was_rmapped && is_large_pte(*sptep))
 		++vcpu->kvm->stat.lpages;
 
@@ -2749,6 +2747,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, int write,
 	if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
 		return RET_PF_RETRY;
 
+	trace_kvm_mmu_spte_requested(gpa, level, pfn);
 	for_each_shadow_entry(vcpu, gpa, it) {
 		base_gfn = gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
 		if (it.level == level)

arch/x86/kvm/mmutrace.h

@@ -322,6 +322,65 @@ TRACE_EVENT(
 		  __entry->kvm_gen == __entry->spte_gen
 	)
 );
+
+TRACE_EVENT(
+	kvm_mmu_set_spte,
+	TP_PROTO(int level, gfn_t gfn, u64 *sptep),
+	TP_ARGS(level, gfn, sptep),
+
+	TP_STRUCT__entry(
+		__field(u64, gfn)
+		__field(u64, spte)
+		__field(u64, sptep)
+		__field(u8, level)
+		/* These depend on page entry type, so compute them now.  */
+		__field(bool, r)
+		__field(bool, x)
+		__field(u8, u)
+	),
+
+	TP_fast_assign(
+		__entry->gfn = gfn;
+		__entry->spte = *sptep;
+		__entry->sptep = virt_to_phys(sptep);
+		__entry->level = level;
+		__entry->r = __entry->spte & PT_PRESENT_MASK;
+		__entry->x = (__entry->spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask;
+		__entry->u = shadow_user_mask ? !!(__entry->spte & shadow_user_mask) : -1;
+	),
+
+	TP_printk("gfn %llx spte %llx (%s%s%s%s) level %d at %llx",
+		  __entry->gfn, __entry->spte,
+		  __entry->r ? "r" : "-",
+		  __entry->spte & PT_WRITABLE_MASK ? "w" : "-",
+		  __entry->x ? "x" : "-",
+		  __entry->u == -1 ? "" : (__entry->u ? "u" : "-"),
+		  __entry->level, __entry->sptep
+	)
+);
+
+TRACE_EVENT(
+	kvm_mmu_spte_requested,
+	TP_PROTO(gpa_t addr, int level, pfn_t pfn),
+	TP_ARGS(addr, level, pfn),
+
+	TP_STRUCT__entry(
+		__field(u64, gfn)
+		__field(u64, pfn)
+		__field(u8, level)
+	),
+
+	TP_fast_assign(
+		__entry->gfn = addr >> PAGE_SHIFT;
+		__entry->pfn = pfn | (__entry->gfn & (KVM_PAGES_PER_HPAGE(level) - 1));
+		__entry->level = level;
+	),
+
+	TP_printk("gfn %llx pfn %llx level %d",
+		  __entry->gfn, __entry->pfn, __entry->level
+	)
+);
+
 #endif /* _TRACE_KVMMMU_H */
 
 #undef TRACE_INCLUDE_PATH

arch/x86/kvm/paging_tmpl.h

@@ -605,6 +605,8 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 
 	base_gfn = gw->gfn;
 
+	trace_kvm_mmu_spte_requested(addr, gw->level, pfn);
+
 	for (; shadow_walk_okay(&it); shadow_walk_next(&it)) {
 		clear_sp_write_flooding_count(it.sptep);
 		base_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);