KVM: x86/mmu: Delete rmap_printk() and all its usage

Delete rmap_printk() so that MMU_WARN_ON() and MMU_DEBUG can be morphed
into something that can be regularly enabled for debug kernels.  The
information provided by rmap_printk() isn't all that useful now that the
rmap and unsync code is mature, as the prints are simultaneously too
verbose (_lots_ of message) and yet not verbose enough to be helpful for
debug (most instances print just the SPTE pointer/value, which is rarely
sufficient to root cause anything but trivial bugs).

Alternatively, rmap_printk() could be reworked to into tracepoints, but
it's not clear there is a real need as rmap bugs rarely escape initial
development, and when bugs do escape to production, they are often edge
cases and/or reside in code that isn't directly related to the rmaps.
In other words, the problems with rmap_printk() being unhelpful also apply
to tracepoints.  And deleting rmap_printk() doesn't preclude adding
tracepoints in the future.

Link: https://lore.kernel.org/r/20230729004722.1056172-3-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -937,10 +937,8 @@ static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte,
 	int count = 0;
 
 	if (!rmap_head->val) {
-		rmap_printk("%p %llx 0->1\n", spte, *spte);
 		rmap_head->val = (unsigned long)spte;
 	} else if (!(rmap_head->val & 1)) {
-		rmap_printk("%p %llx 1->many\n", spte, *spte);
 		desc = kvm_mmu_memory_cache_alloc(cache);
 		desc->sptes[0] = (u64 *)rmap_head->val;
 		desc->sptes[1] = spte;
@@ -949,7 +947,6 @@ static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte,
 		rmap_head->val = (unsigned long)desc | 1;
 		++count;
 	} else {
-		rmap_printk("%p %llx many->many\n", spte, *spte);
 		desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
 		count = desc->tail_count + desc->spte_count;
 
@@ -1014,14 +1011,12 @@ static void pte_list_remove(u64 *spte, struct kvm_rmap_head *rmap_head)
 		pr_err("%s: %p 0->BUG\n", __func__, spte);
 		BUG();
 	} else if (!(rmap_head->val & 1)) {
-		rmap_printk("%p 1->0\n", spte);
 		if ((u64 *)rmap_head->val != spte) {
 			pr_err("%s:  %p 1->BUG\n", __func__, spte);
 			BUG();
 		}
 		rmap_head->val = 0;
 	} else {
-		rmap_printk("%p many->many\n", spte);
 		desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
 		while (desc) {
 			for (i = 0; i < desc->spte_count; ++i) {
@@ -1237,8 +1232,6 @@ static bool spte_write_protect(u64 *sptep, bool pt_protect)
 	    !(pt_protect && is_mmu_writable_spte(spte)))
 		return false;
 
-	rmap_printk("spte %p %llx\n", sptep, *sptep);
-
 	if (pt_protect)
 		spte &= ~shadow_mmu_writable_mask;
 	spte = spte & ~PT_WRITABLE_MASK;
@@ -1263,8 +1256,6 @@ static bool spte_clear_dirty(u64 *sptep)
 {
 	u64 spte = *sptep;
 
-	rmap_printk("spte %p %llx\n", sptep, *sptep);
-
 	MMU_WARN_ON(!spte_ad_enabled(spte));
 	spte &= ~shadow_dirty_mask;
 	return mmu_spte_update(sptep, spte);
@@ -1476,9 +1467,6 @@ static bool kvm_set_pte_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
 
 restart:
 	for_each_rmap_spte(rmap_head, &iter, sptep) {
-		rmap_printk("spte %p %llx gfn %llx (%d)\n",
-			    sptep, *sptep, gfn, level);
-
 		need_flush = true;
 
 		if (pte_write(pte)) {

arch/x86/kvm/mmu/mmu_internal.h

@@ -11,10 +11,8 @@
 #ifdef MMU_DEBUG
 extern bool dbg;
 
-#define rmap_printk(fmt, args...) do { if (dbg) printk("%s: " fmt, __func__, ## args); } while (0)
 #define MMU_WARN_ON(x) WARN_ON(x)
 #else
-#define rmap_printk(x...) do { } while (0)
 #define MMU_WARN_ON(x) do { } while (0)
 #endif