Re: [ANNOUNCE] kvm-46 release

[Gerd Hoffmann <kraxel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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Avi Kivity wrote:
> Gerd Hoffmann wrote:
>> Avi Kivity wrote:
>>   
>>> We've now switched to allocating guest memory in userspace rather than
>>> in the kernel.
>>>     
>> Hmm, a quick glimpse over kvmctl.h doesn't show an obvious way how to
>> use that.  If I want to back vm memory with a file mapping, how can I do
>> that?
>>   
> 
> kvmctl.h doesn't expose an API for that currently, though is should be
> fairly trivial to do so.

Something like this? (compiles, not tested yet).

cheers,
  Gerd


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* make kvm_create() skip all memory setup in case phys_mem_bytes == 0
* add kvm_register_userspace_phys_mem() to register any userspace memory
  as guest physical memory.

Signed-off-by: Gerd Hoffmann <kraxel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 user/kvmctl.c |   53 +++++++++++++++++++++++++++++++++++++++++------------
 user/kvmctl.h |    3 +++
 2 files changed, 44 insertions(+), 12 deletions(-)

Index: kvm-46/user/kvmctl.c
===================================================================
--- kvm-46.orig/user/kvmctl.c
+++ kvm-46/user/kvmctl.c
@@ -443,20 +443,22 @@ int kvm_create(kvm_context_t kvm, unsign
 	}
 	kvm->vm_fd = fd;
 
-	r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_USER_MEMORY);
-	if (r > 0)
-		r = kvm_alloc_userspace_memory(kvm, memory, vm_mem);
-	else
-		r = kvm_alloc_kernel_memory(kvm, memory, vm_mem);
-	if (r < 0)
-		return r;
+	if (phys_mem_bytes) {
+		r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_USER_MEMORY);
+		if (r > 0)
+			r = kvm_alloc_userspace_memory(kvm, memory, vm_mem);
+		else
+			r = kvm_alloc_kernel_memory(kvm, memory, vm_mem);
+		if (r < 0)
+			return r;
 
-        zfd = open("/dev/zero", O_RDONLY);
-        mmap(*vm_mem + 0xa8000, 0x8000, PROT_READ|PROT_WRITE,
-             MAP_PRIVATE|MAP_FIXED, zfd, 0);
-        close(zfd);
+	        zfd = open("/dev/zero", O_RDONLY);
+	        mmap(*vm_mem + 0xa8000, 0x8000, PROT_READ|PROT_WRITE,
+	             MAP_PRIVATE|MAP_FIXED, zfd, 0);
+	        close(zfd);
 
-	kvm->physical_memory = *vm_mem;
+		kvm->physical_memory = *vm_mem;
+	}
 
 	kvm->irqchip_in_kernel = 0;
 	if (!kvm->no_irqchip_creation) {
@@ -558,6 +560,33 @@ void *kvm_create_phys_mem(kvm_context_t 
 								log, writable);
 }
 
+int kvm_register_userspace_phys_mem(kvm_context_t kvm,
+			unsigned long phys_start, void *userspace_addr,
+			unsigned long len, int slot, int log)
+{
+	int r;
+	struct kvm_userspace_memory_region memory = {
+		.slot = slot,
+		.memory_size = len,
+		.guest_phys_addr = phys_start,
+		.userspace_addr = (intptr_t)userspace_addr,
+		.flags = log ? KVM_MEM_LOG_DIRTY_PAGES : 0,
+	};
+
+	if (!kvm->physical_memory)
+		kvm->physical_memory = userspace_addr - phys_start;
+
+	r = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, &memory);
+	if (r == -1) {
+		fprintf(stderr, "create_userspace_phys_mem: %s", strerror(errno));
+		return -1;
+	}
+
+	kvm_userspace_memory_region_save_params(kvm, &memory);
+
+	return 0;
+}
+
 /* destroy/free a whole slot.
  * phys_start, len and slot are the params passed to kvm_create_phys_mem()
  */
Index: kvm-46/user/kvmctl.h
===================================================================
--- kvm-46.orig/user/kvmctl.h
+++ kvm-46/user/kvmctl.h
@@ -404,6 +404,9 @@ void *kvm_create_phys_mem(kvm_context_t,
 			  unsigned long len, int slot, int log, int writable);
 void kvm_destroy_phys_mem(kvm_context_t, unsigned long phys_start, 
 			  unsigned long len, int slot);
+int kvm_register_userspace_phys_mem(kvm_context_t kvm,
+			unsigned long phys_start, void *userspace_addr,
+			unsigned long len, int slot, int log);
 int kvm_get_dirty_pages(kvm_context_t, int slot, void *buf);
 
 

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