Re: [patch] kvmctl.c: allow custom memory setup.

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

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Avi Kivity wrote:
> Izik Eidus wrote:
>> On Thu, 2007-10-18 at 12:18 +0200, Gerd Hoffmann wrote:
>> 
>>>>> I don't see how I can pass a pointer to
>>>>> kvm_create_userspace_memory() via kvm_create() without
>>>>> breaking the libkvm interface.  There is no flags field or
>>>>> similar which could be used to signal "vm_mem is a valid 
>>>>> pointer, please use that instead of mmap()'ing anonymous
>>>>> memory".
>>>>> 
>>>> There is no need to keep binary compat to libkvm as long as it
>>>> is linked statically.

>> anyone who use kvmctl, should not call kvm_create_userspace_memory 
>> directly, instead should call kvm_create()...

I'm talking about the kvm_create() interface, dammit.  Sure I can modify
kvm_create_userspace_memory() without breaking anyone as this isn't part
of the public (kvmctl.h) interface.  That doesn't buy us much though.
I'd have to pass the pointer to kvm_create() somehow so it can be passed
down to kvm_create_userspace_memory().  I can't without breaking the
public library interface though.

> Why not have an API for creating memory slots?  It allows much more 
> flexibility and is more in line with what qemu wants.

This *is* what the patch does.  It adds a function to add a
userspace-memory-backed memory slot: kvm_register_userspace_phys_mem().

That alone doesn't cut it though as there are some more constrains:

 * kvm_create() builds a standard memory layout, which I want be able
   to skip.
 * kvm_create() fails to create a vcpu in case no memory is available,
   which makes simple approach to just ask kvm_create() for 0 bytes
   physical memory for the guest unusable.

Thats why I went the route to additionally split the job kvm_create()
does into multiple, individually callable pieces.  So I can first create
the vm, then create my custom memory slots (instead of the standard
setup built by kvm_create_userspace_memory()), then create the vcpu.

cheers,
  Gerd

ps: patch attached again for reference.

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* split kvm_create() into smaller pieces which can be individually
  called if needed.
* add kvm_register_userspace_phys_mem() function.
---
 user/kvmctl.c |   61 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 user/kvmctl.h |    8 +++++++
 2 files changed, 64 insertions(+), 5 deletions(-)

Index: kvm-46/user/kvmctl.c
===================================================================
--- kvm-46.orig/user/kvmctl.c
+++ kvm-46/user/kvmctl.c
@@ -427,12 +427,9 @@ int kvm_alloc_userspace_memory(kvm_conte
 	return 0;
 }
 
-int kvm_create(kvm_context_t kvm, unsigned long phys_mem_bytes, void **vm_mem)
+int kvm_create_vm(kvm_context_t kvm)
 {
-	unsigned long memory = (phys_mem_bytes + PAGE_SIZE - 1) & PAGE_MASK;
 	int fd = kvm->fd;
-	int zfd;
-	int r;
 
 	kvm->vcpu_fd[0] = -1;
 
@@ -442,6 +439,15 @@ int kvm_create(kvm_context_t kvm, unsign
 		return -1;
 	}
 	kvm->vm_fd = fd;
+	return 0;
+}
+
+int kvm_create_default_phys_mem(kvm_context_t kvm, unsigned long phys_mem_bytes,
+				void **vm_mem)
+{
+	unsigned long memory = (phys_mem_bytes + PAGE_SIZE - 1) & PAGE_MASK;
+	int zfd;
+	int r;
 
 	r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_USER_MEMORY);
 	if (r > 0)
@@ -457,18 +463,37 @@ int kvm_create(kvm_context_t kvm, unsign
         close(zfd);
 
 	kvm->physical_memory = *vm_mem;
+	return 0;
+}
+
+void kvm_create_irqchip(kvm_context_t kvm)
+{
+	int r;
 
 	kvm->irqchip_in_kernel = 0;
 	if (!kvm->no_irqchip_creation) {
 		r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_IRQCHIP);
 		if (r > 0) {	/* kernel irqchip supported */
-			r = ioctl(fd, KVM_CREATE_IRQCHIP);
+			r = ioctl(kvm->vm_fd, KVM_CREATE_IRQCHIP);
 			if (r >= 0)
 				kvm->irqchip_in_kernel = 1;
 			else
 				printf("Create kernel PIC irqchip failed\n");
 		}
 	}
+}
+
+int kvm_create(kvm_context_t kvm, unsigned long phys_mem_bytes, void **vm_mem)
+{
+	int r;
+
+	r = kvm_create_vm(kvm);
+	if (r < 0)
+		return r;
+	r = kvm_create_default_phys_mem(kvm, phys_mem_bytes, vm_mem);
+	if (r < 0)
+		return r;
+	kvm_create_irqchip(kvm);
 	r = kvm_create_vcpu(kvm, 0);
 	if (r < 0)
 		return r;
@@ -558,6 +583,32 @@ 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)
+{
+	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,
+	};
+	int r;
+
+	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
@@ -137,6 +137,11 @@ int kvm_get_shadow_pages(kvm_context_t k
 int kvm_create(kvm_context_t kvm,
 	       unsigned long phys_mem_bytes,
 	       void **phys_mem);
+int kvm_create_vm(kvm_context_t kvm);
+int kvm_create_default_phys_mem(kvm_context_t kvm, unsigned long phys_mem_bytes,
+				void **vm_mem);
+void kvm_create_irqchip(kvm_context_t kvm);
+
 /*!
  * \brief Create a new virtual cpu
  *
@@ -404,6 +409,9 @@ 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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