* [PATCH 1/2] kvm: Introduce get_kvm_from_task
2011-12-16 5:32 [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA zanghongyong
@ 2011-12-16 5:32 ` zanghongyong
2011-12-16 5:32 ` zanghongyong
` (4 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: zanghongyong @ 2011-12-16 5:32 UTC (permalink / raw)
To: linux-kernel
Cc: mst, levinsasha928, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei, Hongyong Zang
From: Hongyong Zang <zanghongyong@huawei.com>
This function finds the kvm structure from its corresponding user
space process, such as qemu process.
Signed-off-by: Hongyong Zang <zanghongyong@huawei.com>
---
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 13 +++++++++++++
2 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8c5c303..1b2f027 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -801,4 +801,4 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
}
#endif
-
+struct kvm *get_kvm_from_task(struct task_struct *task);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e289486..458fe29 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2664,6 +2664,19 @@ static const struct file_operations *stat_fops[] = {
[KVM_STAT_VM] = &vm_stat_fops,
};
+struct kvm* get_kvm_from_task(struct task_struct *task)
+{
+ struct kvm *kvm;
+
+ list_for_each_entry(kvm, &vm_list, vm_list) {
+ if(kvm->mm == task->mm)
+ return kvm;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(get_kvm_from_task);
+
static void kvm_init_debug(void)
{
struct kvm_stats_debugfs_item *p;
--
1.7.1
^ permalink raw reply related [flat|nested] 18+ messages in thread* [PATCH 1/2] kvm: Introduce get_kvm_from_task
2011-12-16 5:32 [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA zanghongyong
2011-12-16 5:32 ` [PATCH 1/2] kvm: Introduce get_kvm_from_task zanghongyong
@ 2011-12-16 5:32 ` zanghongyong
2011-12-16 5:32 ` [PATCH 2/2] vhost-net: Use kvm_memslots for address translation zanghongyong
` (3 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: zanghongyong @ 2011-12-16 5:32 UTC (permalink / raw)
To: linux-kernel
Cc: wusongwei, kvm, mst, netdev, hanweidong, virtualization,
xiaowei.yang, Hongyong Zang, levinsasha928
From: Hongyong Zang <zanghongyong@huawei.com>
This function finds the kvm structure from its corresponding user
space process, such as qemu process.
Signed-off-by: Hongyong Zang <zanghongyong@huawei.com>
---
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 13 +++++++++++++
2 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8c5c303..1b2f027 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -801,4 +801,4 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
}
#endif
-
+struct kvm *get_kvm_from_task(struct task_struct *task);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e289486..458fe29 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2664,6 +2664,19 @@ static const struct file_operations *stat_fops[] = {
[KVM_STAT_VM] = &vm_stat_fops,
};
+struct kvm* get_kvm_from_task(struct task_struct *task)
+{
+ struct kvm *kvm;
+
+ list_for_each_entry(kvm, &vm_list, vm_list) {
+ if(kvm->mm == task->mm)
+ return kvm;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(get_kvm_from_task);
+
static void kvm_init_debug(void)
{
struct kvm_stats_debugfs_item *p;
--
1.7.1
^ permalink raw reply related [flat|nested] 18+ messages in thread* [PATCH 2/2] vhost-net: Use kvm_memslots for address translation
2011-12-16 5:32 [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA zanghongyong
2011-12-16 5:32 ` [PATCH 1/2] kvm: Introduce get_kvm_from_task zanghongyong
2011-12-16 5:32 ` zanghongyong
@ 2011-12-16 5:32 ` zanghongyong
2011-12-16 5:32 ` zanghongyong
` (2 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: zanghongyong @ 2011-12-16 5:32 UTC (permalink / raw)
To: linux-kernel
Cc: wusongwei, kvm, mst, netdev, hanweidong, virtualization,
xiaowei.yang, Hongyong Zang, levinsasha928
From: Hongyong Zang <zanghongyong@huawei.com>
Use kvm's memslots instead of vhost_memory to traslate address
from GPA to HVA.
Signed-off-by: Hongyong Zang <zanghongyong@huawei.com>
---
drivers/vhost/vhost.c | 53 ++++++++++++++++++------------------------------
1 files changed, 20 insertions(+), 33 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c14c42b..63e4322 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -11,6 +11,7 @@
* Generic code for virtio server in host kernel.
*/
+#include <linux/kvm_host.h>
#include <linux/eventfd.h>
#include <linux/vhost.h>
#include <linux/virtio_net.h>
@@ -904,23 +905,6 @@ done:
return r;
}
-static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
- __u64 addr, __u32 len)
-{
- struct vhost_memory_region *reg;
- int i;
-
- /* linear search is not brilliant, but we really have on the order of 6
- * regions in practice */
- for (i = 0; i < mem->nregions; ++i) {
- reg = mem->regions + i;
- if (reg->guest_phys_addr <= addr &&
- reg->guest_phys_addr + reg->memory_size - 1 >= addr)
- return reg;
- }
- return NULL;
-}
-
/* TODO: This is really inefficient. We need something like get_user()
* (instruction directly accesses the data, with an exception table entry
* returning -EFAULT). See Documentation/x86/exception-tables.txt.
@@ -1046,40 +1030,36 @@ int vhost_init_used(struct vhost_virtqueue *vq)
return get_user(vq->last_used_idx, &vq->used->idx);
}
-static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
+static int translate_desc(struct kvm *kvm, u64 addr, u32 len,
struct iovec iov[], int iov_size)
{
- const struct vhost_memory_region *reg;
- struct vhost_memory *mem;
+ const struct kvm_memory_slot *slot;
+ gfn_t gfn = addr >> PAGE_SHIFT;
struct iovec *_iov;
u64 s = 0;
int ret = 0;
- rcu_read_lock();
-
- mem = rcu_dereference(dev->memory);
while ((u64)len > s) {
u64 size;
if (unlikely(ret >= iov_size)) {
ret = -ENOBUFS;
break;
}
- reg = find_region(mem, addr, len);
- if (unlikely(!reg)) {
+ slot = gfn_to_memslot(kvm, gfn);
+ if (unlikely(!slot)) {
ret = -EFAULT;
break;
}
_iov = iov + ret;
- size = reg->memory_size - addr + reg->guest_phys_addr;
+ size = slot->npages*VHOST_PAGE_SIZE - addr + (slot->base_gfn<<PAGE_SHIFT);
_iov->iov_len = min((u64)len, size);
_iov->iov_base = (void __user *)(unsigned long)
- (reg->userspace_addr + addr - reg->guest_phys_addr);
+ (slot->userspace_addr + addr - (slot->base_gfn<<PAGE_SHIFT));
s += size;
addr += size;
++ret;
}
- rcu_read_unlock();
return ret;
}
@@ -1104,7 +1084,7 @@ static unsigned next_desc(struct vring_desc *desc)
return next;
}
-static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
+static int get_indirect(struct kvm *kvm, struct vhost_virtqueue *vq,
struct iovec iov[], unsigned int iov_size,
unsigned int *out_num, unsigned int *in_num,
struct vhost_log *log, unsigned int *log_num,
@@ -1123,7 +1103,7 @@ static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
return -EINVAL;
}
- ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
+ ret = translate_desc(kvm, indirect->addr, indirect->len, vq->indirect,
UIO_MAXIOV);
if (unlikely(ret < 0)) {
vq_err(vq, "Translation failure %d in indirect.\n", ret);
@@ -1163,7 +1143,7 @@ static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
return -EINVAL;
}
- ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
+ ret = translate_desc(kvm, desc.addr, desc.len, iov + iov_count,
iov_size - iov_count);
if (unlikely(ret < 0)) {
vq_err(vq, "Translation failure %d indirect idx %d\n",
@@ -1209,6 +1189,13 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
unsigned int i, head, found = 0;
u16 last_avail_idx;
int ret;
+ struct kvm *kvm = get_kvm_from_task(current);
+
+ if(unlikely(kvm == NULL)){
+ vq_err(vq, "Failed to get corresponding kvm struct of vhost-%d\n",
+ current->pid);
+ return -EFAULT;
+ }
/* Check it isn't doing very strange things with descriptor numbers. */
last_avail_idx = vq->last_avail_idx;
@@ -1274,7 +1261,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
return -EFAULT;
}
if (desc.flags & VRING_DESC_F_INDIRECT) {
- ret = get_indirect(dev, vq, iov, iov_size,
+ ret = get_indirect(kvm, vq, iov, iov_size,
out_num, in_num,
log, log_num, &desc);
if (unlikely(ret < 0)) {
@@ -1285,7 +1272,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
continue;
}
- ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
+ ret = translate_desc(kvm, desc.addr, desc.len, iov + iov_count,
iov_size - iov_count);
if (unlikely(ret < 0)) {
vq_err(vq, "Translation failure %d descriptor idx %d\n",
--
1.7.1
^ permalink raw reply related [flat|nested] 18+ messages in thread* [PATCH 2/2] vhost-net: Use kvm_memslots for address translation
2011-12-16 5:32 [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA zanghongyong
` (2 preceding siblings ...)
2011-12-16 5:32 ` [PATCH 2/2] vhost-net: Use kvm_memslots for address translation zanghongyong
@ 2011-12-16 5:32 ` zanghongyong
2011-12-16 7:05 ` Takuya Yoshikawa
2011-12-16 7:05 ` Sasha Levin
5 siblings, 0 replies; 18+ messages in thread
From: zanghongyong @ 2011-12-16 5:32 UTC (permalink / raw)
To: linux-kernel
Cc: mst, levinsasha928, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei, Hongyong Zang
From: Hongyong Zang <zanghongyong@huawei.com>
Use kvm's memslots instead of vhost_memory to traslate address
from GPA to HVA.
Signed-off-by: Hongyong Zang <zanghongyong@huawei.com>
---
drivers/vhost/vhost.c | 53 ++++++++++++++++++------------------------------
1 files changed, 20 insertions(+), 33 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c14c42b..63e4322 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -11,6 +11,7 @@
* Generic code for virtio server in host kernel.
*/
+#include <linux/kvm_host.h>
#include <linux/eventfd.h>
#include <linux/vhost.h>
#include <linux/virtio_net.h>
@@ -904,23 +905,6 @@ done:
return r;
}
-static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
- __u64 addr, __u32 len)
-{
- struct vhost_memory_region *reg;
- int i;
-
- /* linear search is not brilliant, but we really have on the order of 6
- * regions in practice */
- for (i = 0; i < mem->nregions; ++i) {
- reg = mem->regions + i;
- if (reg->guest_phys_addr <= addr &&
- reg->guest_phys_addr + reg->memory_size - 1 >= addr)
- return reg;
- }
- return NULL;
-}
-
/* TODO: This is really inefficient. We need something like get_user()
* (instruction directly accesses the data, with an exception table entry
* returning -EFAULT). See Documentation/x86/exception-tables.txt.
@@ -1046,40 +1030,36 @@ int vhost_init_used(struct vhost_virtqueue *vq)
return get_user(vq->last_used_idx, &vq->used->idx);
}
-static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
+static int translate_desc(struct kvm *kvm, u64 addr, u32 len,
struct iovec iov[], int iov_size)
{
- const struct vhost_memory_region *reg;
- struct vhost_memory *mem;
+ const struct kvm_memory_slot *slot;
+ gfn_t gfn = addr >> PAGE_SHIFT;
struct iovec *_iov;
u64 s = 0;
int ret = 0;
- rcu_read_lock();
-
- mem = rcu_dereference(dev->memory);
while ((u64)len > s) {
u64 size;
if (unlikely(ret >= iov_size)) {
ret = -ENOBUFS;
break;
}
- reg = find_region(mem, addr, len);
- if (unlikely(!reg)) {
+ slot = gfn_to_memslot(kvm, gfn);
+ if (unlikely(!slot)) {
ret = -EFAULT;
break;
}
_iov = iov + ret;
- size = reg->memory_size - addr + reg->guest_phys_addr;
+ size = slot->npages*VHOST_PAGE_SIZE - addr + (slot->base_gfn<<PAGE_SHIFT);
_iov->iov_len = min((u64)len, size);
_iov->iov_base = (void __user *)(unsigned long)
- (reg->userspace_addr + addr - reg->guest_phys_addr);
+ (slot->userspace_addr + addr - (slot->base_gfn<<PAGE_SHIFT));
s += size;
addr += size;
++ret;
}
- rcu_read_unlock();
return ret;
}
@@ -1104,7 +1084,7 @@ static unsigned next_desc(struct vring_desc *desc)
return next;
}
-static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
+static int get_indirect(struct kvm *kvm, struct vhost_virtqueue *vq,
struct iovec iov[], unsigned int iov_size,
unsigned int *out_num, unsigned int *in_num,
struct vhost_log *log, unsigned int *log_num,
@@ -1123,7 +1103,7 @@ static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
return -EINVAL;
}
- ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
+ ret = translate_desc(kvm, indirect->addr, indirect->len, vq->indirect,
UIO_MAXIOV);
if (unlikely(ret < 0)) {
vq_err(vq, "Translation failure %d in indirect.\n", ret);
@@ -1163,7 +1143,7 @@ static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
return -EINVAL;
}
- ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
+ ret = translate_desc(kvm, desc.addr, desc.len, iov + iov_count,
iov_size - iov_count);
if (unlikely(ret < 0)) {
vq_err(vq, "Translation failure %d indirect idx %d\n",
@@ -1209,6 +1189,13 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
unsigned int i, head, found = 0;
u16 last_avail_idx;
int ret;
+ struct kvm *kvm = get_kvm_from_task(current);
+
+ if(unlikely(kvm == NULL)){
+ vq_err(vq, "Failed to get corresponding kvm struct of vhost-%d\n",
+ current->pid);
+ return -EFAULT;
+ }
/* Check it isn't doing very strange things with descriptor numbers. */
last_avail_idx = vq->last_avail_idx;
@@ -1274,7 +1261,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
return -EFAULT;
}
if (desc.flags & VRING_DESC_F_INDIRECT) {
- ret = get_indirect(dev, vq, iov, iov_size,
+ ret = get_indirect(kvm, vq, iov, iov_size,
out_num, in_num,
log, log_num, &desc);
if (unlikely(ret < 0)) {
@@ -1285,7 +1272,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
continue;
}
- ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
+ ret = translate_desc(kvm, desc.addr, desc.len, iov + iov_count,
iov_size - iov_count);
if (unlikely(ret < 0)) {
vq_err(vq, "Translation failure %d descriptor idx %d\n",
--
1.7.1
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 5:32 [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA zanghongyong
@ 2011-12-16 7:05 ` Takuya Yoshikawa
2011-12-16 5:32 ` zanghongyong
` (4 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: Takuya Yoshikawa @ 2011-12-16 7:05 UTC (permalink / raw)
To: zanghongyong
Cc: wusongwei, kvm, mst, netdev, hanweidong, linux-kernel,
virtualization, xiaowei.yang, levinsasha928
(2011/12/16 14:32), zanghongyong@huawei.com wrote:
> From: Hongyong Zang<zanghongyong@huawei.com>
>
> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
> to translate GPA to HVA. Since kernel's kvm structure already maintains the
> address relationship in its member *kvm_memslots*, these patches use kernel's
> kvm_memslots directly without the need of initialization and maintenance of
> vhost_memory.
Isn't vhost independent from KVM?
Takuya
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
@ 2011-12-16 7:05 ` Takuya Yoshikawa
0 siblings, 0 replies; 18+ messages in thread
From: Takuya Yoshikawa @ 2011-12-16 7:05 UTC (permalink / raw)
To: zanghongyong
Cc: linux-kernel, mst, levinsasha928, kvm, virtualization, netdev,
xiaowei.yang, hanweidong, wusongwei
(2011/12/16 14:32), zanghongyong@huawei.com wrote:
> From: Hongyong Zang<zanghongyong@huawei.com>
>
> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
> to translate GPA to HVA. Since kernel's kvm structure already maintains the
> address relationship in its member *kvm_memslots*, these patches use kernel's
> kvm_memslots directly without the need of initialization and maintenance of
> vhost_memory.
Isn't vhost independent from KVM?
Takuya
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 5:32 [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA zanghongyong
@ 2011-12-16 7:05 ` Sasha Levin
2011-12-16 5:32 ` zanghongyong
` (4 subsequent siblings)
5 siblings, 0 replies; 18+ messages in thread
From: Sasha Levin @ 2011-12-16 7:05 UTC (permalink / raw)
To: zanghongyong
Cc: wusongwei, kvm, mst, netdev, hanweidong, linux-kernel,
virtualization, xiaowei.yang
On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
> From: Hongyong Zang <zanghongyong@huawei.com>
>
> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
> to translate GPA to HVA. Since kernel's kvm structure already maintains the
> address relationship in its member *kvm_memslots*, these patches use kernel's
> kvm_memslots directly without the need of initialization and maintenance of
> vhost_memory.
Conceptually, vhost isn't aware of KVM - it's just a driver which moves
data from vq to a tap device and back. You can't simply add KVM specific
code into vhost.
Whats the performance benefit?
--
Sasha.
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
@ 2011-12-16 7:05 ` Sasha Levin
0 siblings, 0 replies; 18+ messages in thread
From: Sasha Levin @ 2011-12-16 7:05 UTC (permalink / raw)
To: zanghongyong
Cc: linux-kernel, mst, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei
On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
> From: Hongyong Zang <zanghongyong@huawei.com>
>
> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
> to translate GPA to HVA. Since kernel's kvm structure already maintains the
> address relationship in its member *kvm_memslots*, these patches use kernel's
> kvm_memslots directly without the need of initialization and maintenance of
> vhost_memory.
Conceptually, vhost isn't aware of KVM - it's just a driver which moves
data from vq to a tap device and back. You can't simply add KVM specific
code into vhost.
Whats the performance benefit?
--
Sasha.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 7:05 ` Sasha Levin
(?)
@ 2011-12-16 7:40 ` Zang Hongyong
-1 siblings, 0 replies; 18+ messages in thread
From: Zang Hongyong @ 2011-12-16 7:40 UTC (permalink / raw)
To: Sasha Levin
Cc: wusongwei, kvm, mst, netdev, hanweidong, linux-kernel,
virtualization, xiaowei.yang
于 2011/12/16,星期五 15:05, Sasha Levin 写道:
> On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
>> From: Hongyong Zang<zanghongyong@huawei.com>
>>
>> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
>> to translate GPA to HVA. Since kernel's kvm structure already maintains the
>> address relationship in its member *kvm_memslots*, these patches use kernel's
>> kvm_memslots directly without the need of initialization and maintenance of
>> vhost_memory.
> Conceptually, vhost isn't aware of KVM - it's just a driver which moves
> data from vq to a tap device and back. You can't simply add KVM specific
> code into vhost.
>
> Whats the performance benefit?
>
But vhost-net is only used in virtualization situation. vhost_memory is
maintained
by user space qemu.
In this way, the memory relationship can be accquired from kernel
without the
need of maintainence of vhost_memory from qemu.
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 7:05 ` Sasha Levin
(?)
(?)
@ 2011-12-16 7:40 ` Zang Hongyong
2011-12-16 7:59 ` Sasha Levin
-1 siblings, 1 reply; 18+ messages in thread
From: Zang Hongyong @ 2011-12-16 7:40 UTC (permalink / raw)
To: Sasha Levin
Cc: linux-kernel, mst, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei
于 2011/12/16,星期五 15:05, Sasha Levin 写道:
> On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
>> From: Hongyong Zang<zanghongyong@huawei.com>
>>
>> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
>> to translate GPA to HVA. Since kernel's kvm structure already maintains the
>> address relationship in its member *kvm_memslots*, these patches use kernel's
>> kvm_memslots directly without the need of initialization and maintenance of
>> vhost_memory.
> Conceptually, vhost isn't aware of KVM - it's just a driver which moves
> data from vq to a tap device and back. You can't simply add KVM specific
> code into vhost.
>
> Whats the performance benefit?
>
But vhost-net is only used in virtualization situation. vhost_memory is
maintained
by user space qemu.
In this way, the memory relationship can be accquired from kernel
without the
need of maintainence of vhost_memory from qemu.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 7:40 ` Zang Hongyong
@ 2011-12-16 7:59 ` Sasha Levin
0 siblings, 0 replies; 18+ messages in thread
From: Sasha Levin @ 2011-12-16 7:59 UTC (permalink / raw)
To: Zang Hongyong
Cc: wusongwei, kvm, mst, netdev, hanweidong, linux-kernel,
virtualization, xiaowei.yang
On Fri, 2011-12-16 at 15:40 +0800, Zang Hongyong wrote:
> 于 2011/12/16,星期五 15:05, Sasha Levin 写道:
> > On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
> >> From: Hongyong Zang<zanghongyong@huawei.com>
> >>
> >> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
> >> to translate GPA to HVA. Since kernel's kvm structure already maintains the
> >> address relationship in its member *kvm_memslots*, these patches use kernel's
> >> kvm_memslots directly without the need of initialization and maintenance of
> >> vhost_memory.
> > Conceptually, vhost isn't aware of KVM - it's just a driver which moves
> > data from vq to a tap device and back. You can't simply add KVM specific
> > code into vhost.
> >
> > Whats the performance benefit?
> >
> But vhost-net is only used in virtualization situation. vhost_memory is
> maintained
> by user space qemu.
> In this way, the memory relationship can be accquired from kernel
> without the
> need of maintainence of vhost_memory from qemu.
You can't assume that vhost-* is used only along with qemu/kvm. Just as
virtio has more uses than just virtualization (heres one:
https://lkml.org/lkml/2011/10/25/139 ), there are more uses for vhost as
well.
There has been a great deal of effort to keep vhost and kvm untangled.
One example is the memory translation it has to do, another one is the
eventfd/irqfd thing it does just so it could signal an IRQ in the guest
instead of accessing the guest directly.
If you do see a great performance increase when tying vhost and KVM
together, it may be worth it to create some sort of an in-kernel
vhost-kvm bridging thing, but if the performance isn't noticeable we're
better off just leaving it as is and keeping the vhost code general.
--
Sasha.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
@ 2011-12-16 7:59 ` Sasha Levin
0 siblings, 0 replies; 18+ messages in thread
From: Sasha Levin @ 2011-12-16 7:59 UTC (permalink / raw)
To: Zang Hongyong
Cc: linux-kernel, mst, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei
On Fri, 2011-12-16 at 15:40 +0800, Zang Hongyong wrote:
> 于 2011/12/16,星期五 15:05, Sasha Levin 写道:
> > On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
> >> From: Hongyong Zang<zanghongyong@huawei.com>
> >>
> >> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
> >> to translate GPA to HVA. Since kernel's kvm structure already maintains the
> >> address relationship in its member *kvm_memslots*, these patches use kernel's
> >> kvm_memslots directly without the need of initialization and maintenance of
> >> vhost_memory.
> > Conceptually, vhost isn't aware of KVM - it's just a driver which moves
> > data from vq to a tap device and back. You can't simply add KVM specific
> > code into vhost.
> >
> > Whats the performance benefit?
> >
> But vhost-net is only used in virtualization situation. vhost_memory is
> maintained
> by user space qemu.
> In this way, the memory relationship can be accquired from kernel
> without the
> need of maintainence of vhost_memory from qemu.
You can't assume that vhost-* is used only along with qemu/kvm. Just as
virtio has more uses than just virtualization (heres one:
https://lkml.org/lkml/2011/10/25/139 ), there are more uses for vhost as
well.
There has been a great deal of effort to keep vhost and kvm untangled.
One example is the memory translation it has to do, another one is the
eventfd/irqfd thing it does just so it could signal an IRQ in the guest
instead of accessing the guest directly.
If you do see a great performance increase when tying vhost and KVM
together, it may be worth it to create some sort of an in-kernel
vhost-kvm bridging thing, but if the performance isn't noticeable we're
better off just leaving it as is and keeping the vhost code general.
--
Sasha.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 7:59 ` Sasha Levin
@ 2011-12-16 8:07 ` Sasha Levin
-1 siblings, 0 replies; 18+ messages in thread
From: Sasha Levin @ 2011-12-16 8:07 UTC (permalink / raw)
To: Zang Hongyong
Cc: wusongwei, kvm, mst, netdev, hanweidong, linux-kernel,
virtualization, xiaowei.yang
On Fri, 2011-12-16 at 09:59 +0200, Sasha Levin wrote:
> There has been a great deal of effort to keep vhost and kvm untangled.
> One example is the memory translation it has to do, another one is the
> eventfd/irqfd thing it does just so it could signal an IRQ in the guest
> instead of accessing the guest directly.
Actually, CONFIG_VHOST_NET doesn't even depend on CONFIG_KVM, so your
patch will break build when (CONFIG_VHOST_NET=y && CONFIG_KVM=n).
--
Sasha.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
@ 2011-12-16 8:07 ` Sasha Levin
0 siblings, 0 replies; 18+ messages in thread
From: Sasha Levin @ 2011-12-16 8:07 UTC (permalink / raw)
To: Zang Hongyong
Cc: linux-kernel, mst, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei
On Fri, 2011-12-16 at 09:59 +0200, Sasha Levin wrote:
> There has been a great deal of effort to keep vhost and kvm untangled.
> One example is the memory translation it has to do, another one is the
> eventfd/irqfd thing it does just so it could signal an IRQ in the guest
> instead of accessing the guest directly.
Actually, CONFIG_VHOST_NET doesn't even depend on CONFIG_KVM, so your
patch will break build when (CONFIG_VHOST_NET=y && CONFIG_KVM=n).
--
Sasha.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 7:59 ` Sasha Levin
(?)
(?)
@ 2011-12-16 8:18 ` Zang Hongyong
-1 siblings, 0 replies; 18+ messages in thread
From: Zang Hongyong @ 2011-12-16 8:18 UTC (permalink / raw)
To: Sasha Levin
Cc: wusongwei, kvm, mst, netdev, hanweidong, linux-kernel,
virtualization, xiaowei.yang
于 2011/12/16,星期五 15:59, Sasha Levin 写道:
> On Fri, 2011-12-16 at 15:40 +0800, Zang Hongyong wrote:
>> 于 2011/12/16,星期五 15:05, Sasha Levin 写道:
>>> On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
>>>> From: Hongyong Zang<zanghongyong@huawei.com>
>>>>
>>>> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
>>>> to translate GPA to HVA. Since kernel's kvm structure already maintains the
>>>> address relationship in its member *kvm_memslots*, these patches use kernel's
>>>> kvm_memslots directly without the need of initialization and maintenance of
>>>> vhost_memory.
>>> Conceptually, vhost isn't aware of KVM - it's just a driver which moves
>>> data from vq to a tap device and back. You can't simply add KVM specific
>>> code into vhost.
>>>
>>> Whats the performance benefit?
>>>
>> But vhost-net is only used in virtualization situation. vhost_memory is
>> maintained
>> by user space qemu.
>> In this way, the memory relationship can be accquired from kernel
>> without the
>> need of maintainence of vhost_memory from qemu.
> You can't assume that vhost-* is used only along with qemu/kvm. Just as
> virtio has more uses than just virtualization (heres one:
> https://lkml.org/lkml/2011/10/25/139 ), there are more uses for vhost as
> well.
>
> There has been a great deal of effort to keep vhost and kvm untangled.
> One example is the memory translation it has to do, another one is the
> eventfd/irqfd thing it does just so it could signal an IRQ in the guest
> instead of accessing the guest directly.
>
> If you do see a great performance increase when tying vhost and KVM
> together, it may be worth it to create some sort of an in-kernel
> vhost-kvm bridging thing, but if the performance isn't noticeable we're
> better off just leaving it as is and keeping the vhost code general.
>
Thanks for your explanation.
Since memory layout is seldom changed after guest boots, the situation
manily occurs during initialization. There's no need for vhost-kvm
bridge now.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 0/2] vhot-net: Use kvm_memslots instead of vhost_memory to translate GPA to HVA
2011-12-16 7:59 ` Sasha Levin
` (2 preceding siblings ...)
(?)
@ 2011-12-16 8:18 ` Zang Hongyong
-1 siblings, 0 replies; 18+ messages in thread
From: Zang Hongyong @ 2011-12-16 8:18 UTC (permalink / raw)
To: Sasha Levin
Cc: linux-kernel, mst, kvm, virtualization, netdev, xiaowei.yang,
hanweidong, wusongwei
于 2011/12/16,星期五 15:59, Sasha Levin 写道:
> On Fri, 2011-12-16 at 15:40 +0800, Zang Hongyong wrote:
>> 于 2011/12/16,星期五 15:05, Sasha Levin 写道:
>>> On Fri, 2011-12-16 at 13:32 +0800, zanghongyong@huawei.com wrote:
>>>> From: Hongyong Zang<zanghongyong@huawei.com>
>>>>
>>>> Vhost-net uses its own vhost_memory, which results from user space (qemu) info,
>>>> to translate GPA to HVA. Since kernel's kvm structure already maintains the
>>>> address relationship in its member *kvm_memslots*, these patches use kernel's
>>>> kvm_memslots directly without the need of initialization and maintenance of
>>>> vhost_memory.
>>> Conceptually, vhost isn't aware of KVM - it's just a driver which moves
>>> data from vq to a tap device and back. You can't simply add KVM specific
>>> code into vhost.
>>>
>>> Whats the performance benefit?
>>>
>> But vhost-net is only used in virtualization situation. vhost_memory is
>> maintained
>> by user space qemu.
>> In this way, the memory relationship can be accquired from kernel
>> without the
>> need of maintainence of vhost_memory from qemu.
> You can't assume that vhost-* is used only along with qemu/kvm. Just as
> virtio has more uses than just virtualization (heres one:
> https://lkml.org/lkml/2011/10/25/139 ), there are more uses for vhost as
> well.
>
> There has been a great deal of effort to keep vhost and kvm untangled.
> One example is the memory translation it has to do, another one is the
> eventfd/irqfd thing it does just so it could signal an IRQ in the guest
> instead of accessing the guest directly.
>
> If you do see a great performance increase when tying vhost and KVM
> together, it may be worth it to create some sort of an in-kernel
> vhost-kvm bridging thing, but if the performance isn't noticeable we're
> better off just leaving it as is and keeping the vhost code general.
>
Thanks for your explanation.
Since memory layout is seldom changed after guest boots, the situation
manily occurs during initialization. There's no need for vhost-kvm
bridge now.
^ permalink raw reply [flat|nested] 18+ messages in thread