[PATCH 1/4] Swapping

[PATCH 1/4] Swapping

[Izik Eidus]

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this make the rmap keep reverse mapping on all the present shadow pages

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>From 3b5821a55836f82f987b878982cbc6fc8336371f Mon Sep 17 00:00:00 2001
From: Izik Eidus <izik@Home1.(none)>
Date: Sat, 13 Oct 2007 01:47:44 +0200
Subject: [PATCH] modify the rmap so it will hold reverse mapping to all present
shadow pages

Signed-off-by: Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
 drivers/kvm/mmu.c |   52 ++++++++++++++++++++++++++++++++++++----------------
 1 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index f52604a..cfbeec8 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -211,8 +211,8 @@ static int is_io_pte(unsigned long pte)
 
 static int is_rmap_pte(u64 pte)
 {
-	return (pte & (PT_WRITABLE_MASK | PT_PRESENT_MASK))
-		== (PT_WRITABLE_MASK | PT_PRESENT_MASK);
+	return pte != shadow_trap_nonpresent_pte
+		&& pte != shadow_notrap_nonpresent_pte;
 }
 
 static void set_shadow_pte(u64 *sptep, u64 spte)
@@ -456,29 +456,51 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
 	}
 }
 
-static void rmap_write_protect(struct kvm *kvm, u64 gfn)
+static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
 {
 	struct kvm_rmap_desc *desc;
+	struct kvm_rmap_desc *prev_desc;
+	u64 *prev_spte;
+	int i;
+
+	if (!*rmapp)
+		return NULL;
+	else if (!(*rmapp & 1)) {
+		if (!spte)
+			return (u64 *)*rmapp;
+		return NULL;
+	}
+	desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
+	prev_desc = NULL;
+	prev_spte = NULL;
+	while (desc) {
+		for (i = 0; i < RMAP_EXT && desc->shadow_ptes[i]; ++i) {
+			if (prev_spte == spte)
+				return desc->shadow_ptes[i];
+			prev_spte = desc->shadow_ptes[i];
+		}
+		desc = desc->more;
+	}
+	return NULL;
+}
+
+static void rmap_write_protect(struct kvm *kvm, u64 gfn)
+{
 	unsigned long *rmapp;
 	u64 *spte;
 
 	gfn = unalias_gfn(kvm, gfn);
 	rmapp = gfn_to_rmap(kvm, gfn);
 
-	while (*rmapp) {
-		if (!(*rmapp & 1))
-			spte = (u64 *)*rmapp;
-		else {
-			desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
-			spte = desc->shadow_ptes[0];
-		}
+	spte = rmap_next(kvm, rmapp, NULL);
+	while (spte) {
 		BUG_ON(!spte);
 		BUG_ON(!(*spte & PT_PRESENT_MASK));
-		BUG_ON(!(*spte & PT_WRITABLE_MASK));
 		rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
-		rmap_remove(kvm, spte);
-		set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
+		if (is_writeble_pte(*spte))
+			set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
 		kvm_flush_remote_tlbs(kvm);
+		spte = rmap_next(kvm, rmapp, spte);
 	}
 }
 
@@ -1399,10 +1421,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
 		pt = page->spt;
 		for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
 			/* avoid RMW */
-			if (pt[i] & PT_WRITABLE_MASK) {
-				rmap_remove(kvm, &pt[i]);
+			if (pt[i] & PT_WRITABLE_MASK)
 				pt[i] &= ~PT_WRITABLE_MASK;
-			}
 	}
 }
 
-- 
1.5.2.4


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