[patch 3/3] QEMU: balloon: zap any shadow mappings to a page before madvise(MADV_DONTNEED)

[Marcelo Tosatti <mtosatti@redhat.com>]

[-- Attachment #1: virtio-ball1 --]
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Call into kvm to know whether we can madvise(MADV_DONTNEED) pages.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm-userspace.balloon/libkvm/libkvm.c
===================================================================
--- kvm-userspace.balloon.orig/libkvm/libkvm.c
+++ kvm-userspace.balloon/libkvm/libkvm.c
@@ -840,6 +840,20 @@ int kvm_is_ready_for_interrupt_injection
 	return run->ready_for_interrupt_injection;
 }
 
+int kvm_zap_single_gfn(kvm_context_t kvm, unsigned long gfn)
+{
+	int r = -1;
+
+#ifdef KVM_CAP_ZAP_GFN
+	r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_ZAP_GFN);
+	if (r > 0)
+		r = ioctl(kvm->vm_fd, KVM_ZAP_GFN, &gfn);
+	else
+		r = -1;
+#endif
+	return r;
+}
+
 int kvm_run(kvm_context_t kvm, int vcpu)
 {
 	int r;
Index: kvm-userspace.balloon/libkvm/libkvm.h
===================================================================
--- kvm-userspace.balloon.orig/libkvm/libkvm.h
+++ kvm-userspace.balloon/libkvm/libkvm.h
@@ -422,6 +422,7 @@ int kvm_get_dirty_pages_range(kvm_contex
 			      unsigned long end_addr, void *buf, void*opaque,
 			      int (*cb)(unsigned long start, unsigned long len,
 					void*bitmap, void *opaque));
+int kvm_zap_single_gfn(kvm_context_t kvm, unsigned long gfn);
 
 /*!
  * \brief Create a memory alias
Index: kvm-userspace.balloon/qemu/hw/virtio-balloon.c
===================================================================
--- kvm-userspace.balloon.orig/qemu/hw/virtio-balloon.c
+++ kvm-userspace.balloon/qemu/hw/virtio-balloon.c
@@ -17,6 +17,7 @@
 #include "balloon.h"
 #include "sysemu.h"
 #include "console.h"
+#include "qemu-kvm.h"
 
 #include <sys/mman.h>
 
@@ -60,22 +61,21 @@ static void virtio_balloon_handle_output
 	unsigned int wlen = 0;
 
 	for (i = 0; i < elem.out_num; i++) {
-	    int flags;
 	    uint32_t *pfns = elem.out_sg[i].iov_base;
 	    unsigned int n_pfns = elem.out_sg[i].iov_len / 4;
 	    int j;
 
 	    for (j = 0; j < n_pfns; j++) {
-		if (vq == s->dvq) /* deflate */
-		    flags = MADV_WILLNEED;
-		else /* inflate */
-		    flags = MADV_DONTNEED;
-
-#if 0
-		/* can't use this until we have mmu notifier support */
-		madvise(phys_ram_base + (pfns[j] << TARGET_PAGE_BITS),
-			TARGET_PAGE_SIZE, flags);
-#endif
+		if (vq == s->dvq)
+                    /* deflate */
+		        madvise(phys_ram_base + (pfns[j] << TARGET_PAGE_BITS),
+			        TARGET_PAGE_SIZE, MADV_WILLNEED);
+		else { /* inflate */
+			if (kvm_zap_gfn(pfns[j]) == 0)
+				madvise(phys_ram_base +
+					(pfns[j] << TARGET_PAGE_BITS),
+					TARGET_PAGE_SIZE, MADV_DONTNEED);
+		}
 	    }
 
 	    wlen += elem.out_sg[i].iov_len;
Index: kvm-userspace.balloon/qemu/qemu-kvm.c
===================================================================
--- kvm-userspace.balloon.orig/qemu/qemu-kvm.c
+++ kvm-userspace.balloon/qemu/qemu-kvm.c
@@ -65,6 +65,11 @@ static void sig_ipi_handler(int n)
 {
 }
 
+int kvm_zap_gfn(unsigned long gfn)
+{
+	return kvm_zap_single_gfn(kvm_context, gfn);
+}
+
 void kvm_update_interrupt_request(CPUState *env)
 {
     if (env && vcpu && env != vcpu->env) {
Index: kvm-userspace.balloon/qemu/qemu-kvm.h
===================================================================
--- kvm-userspace.balloon.orig/qemu/qemu-kvm.h
+++ kvm-userspace.balloon/qemu/qemu-kvm.h
@@ -24,6 +24,7 @@ int kvm_qemu_init_env(CPUState *env);
 int kvm_qemu_check_extension(int ext);
 void kvm_apic_init(CPUState *env);
 int kvm_set_irq(int irq, int level);
+int kvm_zap_gfn(unsigned long gfn);
 
 int kvm_physical_memory_set_dirty_tracking(int enable);
 int kvm_update_dirty_pages_log(void);

-- 


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