Checking whether the memory regions are equal is sufficient: if they are
equal, then most certainly the contained fd is equal.
The whole vhost-user memslot handling is suboptimal and overly
complicated. We shouldn't have to lookup a RAM memory regions we got
notified about in vhost_user_get_mr_data() using a host pointer. But that
requires a bigger rework -- especially an alternative vhost_set_mem_table()
backend call that simply consumes MemoryRegionSections.
For now, let's just drop vhost_backend_can_merge().
Signed-off-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/vhost-user.c | 14 --------------
hw/virtio/vhost-vdpa.c | 1 -
hw/virtio/vhost.c | 6 +-----
include/hw/virtio/vhost-backend.h | 4 ----
4 files changed, 1 insertion(+), 24 deletions(-)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index e68daa35d4..4bfaf559a7 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2195,19 +2195,6 @@ static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
return -ENOTSUP;
}
-static bool vhost_user_can_merge(struct vhost_dev *dev,
- uint64_t start1, uint64_t size1,
- uint64_t start2, uint64_t size2)
-{
- ram_addr_t offset;
- int mfd, rfd;
-
- (void)vhost_user_get_mr_data(start1, &offset, &mfd);
- (void)vhost_user_get_mr_data(start2, &offset, &rfd);
-
- return mfd == rfd;
-}
-
static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
{
VhostUserMsg msg;
@@ -2704,7 +2691,6 @@ const VhostOps user_ops = {
.vhost_set_vring_enable = vhost_user_set_vring_enable,
.vhost_requires_shm_log = vhost_user_requires_shm_log,
.vhost_migration_done = vhost_user_migration_done,
- .vhost_backend_can_merge = vhost_user_can_merge,
.vhost_net_set_mtu = vhost_user_net_set_mtu,
.vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
.vhost_send_device_iotlb_msg = vhost_user_send_device_iotlb_msg,
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 542e003101..9ab7bc8718 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1317,7 +1317,6 @@ const VhostOps vdpa_ops = {
.vhost_set_config = vhost_vdpa_set_config,
.vhost_requires_shm_log = NULL,
.vhost_migration_done = NULL,
- .vhost_backend_can_merge = NULL,
.vhost_net_set_mtu = NULL,
.vhost_set_iotlb_callback = NULL,
.vhost_send_device_iotlb_msg = NULL,
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index b7fb960fa9..9d8662aa98 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -733,11 +733,7 @@ static void vhost_region_add_section(struct vhost_dev *dev,
size_t offset = mrs_gpa - prev_gpa_start;
if (prev_host_start + offset == mrs_host &&
- section->mr == prev_sec->mr &&
- (!dev->vhost_ops->vhost_backend_can_merge ||
- dev->vhost_ops->vhost_backend_can_merge(dev,
- mrs_host, mrs_size,
- prev_host_start, prev_size))) {
+ section->mr == prev_sec->mr) {
uint64_t max_end = MAX(prev_host_end, mrs_host + mrs_size);
need_add = false;
prev_sec->offset_within_address_space =
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index c5ab49051e..abf1601ba2 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -86,9 +86,6 @@ typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
char *mac_addr);
-typedef bool (*vhost_backend_can_merge_op)(struct vhost_dev *dev,
- uint64_t start1, uint64_t size1,
- uint64_t start2, uint64_t size2);
typedef int (*vhost_vsock_set_guest_cid_op)(struct vhost_dev *dev,
uint64_t guest_cid);
typedef int (*vhost_vsock_set_running_op)(struct vhost_dev *dev, int start);
@@ -160,7 +157,6 @@ typedef struct VhostOps {
vhost_set_vring_enable_op vhost_set_vring_enable;
vhost_requires_shm_log_op vhost_requires_shm_log;
vhost_migration_done_op vhost_migration_done;
- vhost_backend_can_merge_op vhost_backend_can_merge;
vhost_vsock_set_guest_cid_op vhost_vsock_set_guest_cid;
vhost_vsock_set_running_op vhost_vsock_set_running;
vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
--
2.39.1On Thu, 16 Feb 2023 12:47:52 +0100
David Hildenbrand <david@redhat.com> wrote:
> Checking whether the memory regions are equal is sufficient: if they are
> equal, then most certainly the contained fd is equal.
sounds reasonable to me.
>
> The whole vhost-user memslot handling is suboptimal and overly
> complicated. We shouldn't have to lookup a RAM memory regions we got
> notified about in vhost_user_get_mr_data() using a host pointer. But that
While on janitor duty can you fixup following?
vhost_user_get_mr_data() -> memory_region_from_host ->
-> qemu_ram_block_from_host()
for qemu_ram_block_from_host doc comment seems to out of
sync (ram_addr not longer exists)
> requires a bigger rework -- especially an alternative vhost_set_mem_table()
> backend call that simply consumes MemoryRegionSections.
just skimming through usage of vhost_user_get_mr_data() it looks like
we are first collecting MemoryRegionSection-s into tmp_sections
then we do vhost_commit we convert then into vhost_memory_region list
and the we are trying hard to convert addresses from the later
to back to MemoryRegions we've lost during tmp_sections conversion
all over the place.
To me it looks like we should drop conversion to vhost_dev::mem
and replace its usage with vhost_dev::mem_sections directly
to get rid of data duplication and back and forth addr<->mr conversion.
> For now, let's just drop vhost_backend_can_merge().
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> ---
> hw/virtio/vhost-user.c | 14 --------------
> hw/virtio/vhost-vdpa.c | 1 -
> hw/virtio/vhost.c | 6 +-----
> include/hw/virtio/vhost-backend.h | 4 ----
> 4 files changed, 1 insertion(+), 24 deletions(-)
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index e68daa35d4..4bfaf559a7 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -2195,19 +2195,6 @@ static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
> return -ENOTSUP;
> }
>
> -static bool vhost_user_can_merge(struct vhost_dev *dev,
> - uint64_t start1, uint64_t size1,
> - uint64_t start2, uint64_t size2)
> -{
> - ram_addr_t offset;
> - int mfd, rfd;
> -
> - (void)vhost_user_get_mr_data(start1, &offset, &mfd);
> - (void)vhost_user_get_mr_data(start2, &offset, &rfd);
> -
> - return mfd == rfd;
> -}
> -
> static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
> {
> VhostUserMsg msg;
> @@ -2704,7 +2691,6 @@ const VhostOps user_ops = {
> .vhost_set_vring_enable = vhost_user_set_vring_enable,
> .vhost_requires_shm_log = vhost_user_requires_shm_log,
> .vhost_migration_done = vhost_user_migration_done,
> - .vhost_backend_can_merge = vhost_user_can_merge,
> .vhost_net_set_mtu = vhost_user_net_set_mtu,
> .vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
> .vhost_send_device_iotlb_msg = vhost_user_send_device_iotlb_msg,
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 542e003101..9ab7bc8718 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -1317,7 +1317,6 @@ const VhostOps vdpa_ops = {
> .vhost_set_config = vhost_vdpa_set_config,
> .vhost_requires_shm_log = NULL,
> .vhost_migration_done = NULL,
> - .vhost_backend_can_merge = NULL,
> .vhost_net_set_mtu = NULL,
> .vhost_set_iotlb_callback = NULL,
> .vhost_send_device_iotlb_msg = NULL,
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index b7fb960fa9..9d8662aa98 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -733,11 +733,7 @@ static void vhost_region_add_section(struct vhost_dev *dev,
> size_t offset = mrs_gpa - prev_gpa_start;
>
> if (prev_host_start + offset == mrs_host &&
> - section->mr == prev_sec->mr &&
> - (!dev->vhost_ops->vhost_backend_can_merge ||
> - dev->vhost_ops->vhost_backend_can_merge(dev,
> - mrs_host, mrs_size,
> - prev_host_start, prev_size))) {
> + section->mr == prev_sec->mr) {
> uint64_t max_end = MAX(prev_host_end, mrs_host + mrs_size);
> need_add = false;
> prev_sec->offset_within_address_space =
> diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> index c5ab49051e..abf1601ba2 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -86,9 +86,6 @@ typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
> typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
> typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
> char *mac_addr);
> -typedef bool (*vhost_backend_can_merge_op)(struct vhost_dev *dev,
> - uint64_t start1, uint64_t size1,
> - uint64_t start2, uint64_t size2);
> typedef int (*vhost_vsock_set_guest_cid_op)(struct vhost_dev *dev,
> uint64_t guest_cid);
> typedef int (*vhost_vsock_set_running_op)(struct vhost_dev *dev, int start);
> @@ -160,7 +157,6 @@ typedef struct VhostOps {
> vhost_set_vring_enable_op vhost_set_vring_enable;
> vhost_requires_shm_log_op vhost_requires_shm_log;
> vhost_migration_done_op vhost_migration_done;
> - vhost_backend_can_merge_op vhost_backend_can_merge;
> vhost_vsock_set_guest_cid_op vhost_vsock_set_guest_cid;
> vhost_vsock_set_running_op vhost_vsock_set_running;
> vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
On Tue, 7 Mar 2023 11:25:48 +0100
Igor Mammedov <imammedo@redhat.com> wrote:
> On Thu, 16 Feb 2023 12:47:52 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
> > Checking whether the memory regions are equal is sufficient: if they are
> > equal, then most certainly the contained fd is equal.
> sounds reasonable to me.
>
> >
> > The whole vhost-user memslot handling is suboptimal and overly
> > complicated. We shouldn't have to lookup a RAM memory regions we got
> > notified about in vhost_user_get_mr_data() using a host pointer. But that
>
> While on janitor duty can you fixup following?
>
> vhost_user_get_mr_data() -> memory_region_from_host ->
> -> qemu_ram_block_from_host()
> for qemu_ram_block_from_host doc comment seems to out of
> sync (ram_addr not longer exists)
>
> > requires a bigger rework -- especially an alternative vhost_set_mem_table()
> > backend call that simply consumes MemoryRegionSections.
>
> just skimming through usage of vhost_user_get_mr_data() it looks like
> we are first collecting MemoryRegionSection-s into tmp_sections
> then we do vhost_commit we convert then into vhost_memory_region list
> and the we are trying hard to convert addresses from the later
> to back to MemoryRegions we've lost during tmp_sections conversion
> all over the place.
>
> To me it looks like we should drop conversion to vhost_dev::mem
> and replace its usage with vhost_dev::mem_sections directly
> to get rid of data duplication and back and forth addr<->mr conversion.
>
> > For now, let's just drop vhost_backend_can_merge().
> >
> > Signed-off-by: David Hildenbrand <david@redhat.com>
>
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>
> > ---
> > hw/virtio/vhost-user.c | 14 --------------
> > hw/virtio/vhost-vdpa.c | 1 -
> > hw/virtio/vhost.c | 6 +-----
> > include/hw/virtio/vhost-backend.h | 4 ----
> > 4 files changed, 1 insertion(+), 24 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index e68daa35d4..4bfaf559a7 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -2195,19 +2195,6 @@ static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
> > return -ENOTSUP;
> > }
> >
> > -static bool vhost_user_can_merge(struct vhost_dev *dev,
> > - uint64_t start1, uint64_t size1,
> > - uint64_t start2, uint64_t size2)
> > -{
> > - ram_addr_t offset;
> > - int mfd, rfd;
> > -
> > - (void)vhost_user_get_mr_data(start1, &offset, &mfd);
> > - (void)vhost_user_get_mr_data(start2, &offset, &rfd);
> > -
> > - return mfd == rfd;
> > -}
> > -
> > static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
> > {
> > VhostUserMsg msg;
> > @@ -2704,7 +2691,6 @@ const VhostOps user_ops = {
> > .vhost_set_vring_enable = vhost_user_set_vring_enable,
> > .vhost_requires_shm_log = vhost_user_requires_shm_log,
> > .vhost_migration_done = vhost_user_migration_done,
> > - .vhost_backend_can_merge = vhost_user_can_merge,
> > .vhost_net_set_mtu = vhost_user_net_set_mtu,
> > .vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
> > .vhost_send_device_iotlb_msg = vhost_user_send_device_iotlb_msg,
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 542e003101..9ab7bc8718 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1317,7 +1317,6 @@ const VhostOps vdpa_ops = {
> > .vhost_set_config = vhost_vdpa_set_config,
> > .vhost_requires_shm_log = NULL,
> > .vhost_migration_done = NULL,
> > - .vhost_backend_can_merge = NULL,
> > .vhost_net_set_mtu = NULL,
> > .vhost_set_iotlb_callback = NULL,
> > .vhost_send_device_iotlb_msg = NULL,
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index b7fb960fa9..9d8662aa98 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -733,11 +733,7 @@ static void vhost_region_add_section(struct vhost_dev *dev,
> > size_t offset = mrs_gpa - prev_gpa_start;
> >
> > if (prev_host_start + offset == mrs_host &&
> > - section->mr == prev_sec->mr &&
> > - (!dev->vhost_ops->vhost_backend_can_merge ||
> > - dev->vhost_ops->vhost_backend_can_merge(dev,
another question, can it relly happen, i.e. having 2 abut memory sections
with the same memory region, is yes then when/why?
> > - mrs_host, mrs_size,
> > - prev_host_start, prev_size))) {
> > + section->mr == prev_sec->mr) {
> > uint64_t max_end = MAX(prev_host_end, mrs_host + mrs_size);
> > need_add = false;
> > prev_sec->offset_within_address_space =
> > diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> > index c5ab49051e..abf1601ba2 100644
> > --- a/include/hw/virtio/vhost-backend.h
> > +++ b/include/hw/virtio/vhost-backend.h
> > @@ -86,9 +86,6 @@ typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
> > typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
> > typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
> > char *mac_addr);
> > -typedef bool (*vhost_backend_can_merge_op)(struct vhost_dev *dev,
> > - uint64_t start1, uint64_t size1,
> > - uint64_t start2, uint64_t size2);
> > typedef int (*vhost_vsock_set_guest_cid_op)(struct vhost_dev *dev,
> > uint64_t guest_cid);
> > typedef int (*vhost_vsock_set_running_op)(struct vhost_dev *dev, int start);
> > @@ -160,7 +157,6 @@ typedef struct VhostOps {
> > vhost_set_vring_enable_op vhost_set_vring_enable;
> > vhost_requires_shm_log_op vhost_requires_shm_log;
> > vhost_migration_done_op vhost_migration_done;
> > - vhost_backend_can_merge_op vhost_backend_can_merge;
> > vhost_vsock_set_guest_cid_op vhost_vsock_set_guest_cid;
> > vhost_vsock_set_running_op vhost_vsock_set_running;
> > vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
>
On 07.03.23 12:16, Igor Mammedov wrote:
> On Tue, 7 Mar 2023 11:25:48 +0100
> Igor Mammedov <imammedo@redhat.com> wrote:
>
>> On Thu, 16 Feb 2023 12:47:52 +0100
>> David Hildenbrand <david@redhat.com> wrote:
>>
>>> Checking whether the memory regions are equal is sufficient: if they are
>>> equal, then most certainly the contained fd is equal.
>> sounds reasonable to me.
>>
>>>
>>> The whole vhost-user memslot handling is suboptimal and overly
>>> complicated. We shouldn't have to lookup a RAM memory regions we got
>>> notified about in vhost_user_get_mr_data() using a host pointer. But that
>>
>> While on janitor duty can you fixup following?
>>
>> vhost_user_get_mr_data() -> memory_region_from_host ->
>> -> qemu_ram_block_from_host()
>> for qemu_ram_block_from_host doc comment seems to out of
>> sync (ram_addr not longer exists)
>>
>>> requires a bigger rework -- especially an alternative vhost_set_mem_table()
>>> backend call that simply consumes MemoryRegionSections.
>>
>> just skimming through usage of vhost_user_get_mr_data() it looks like
>> we are first collecting MemoryRegionSection-s into tmp_sections
>> then we do vhost_commit we convert then into vhost_memory_region list
>> and the we are trying hard to convert addresses from the later
>> to back to MemoryRegions we've lost during tmp_sections conversion
>> all over the place.
>>
>> To me it looks like we should drop conversion to vhost_dev::mem
>> and replace its usage with vhost_dev::mem_sections directly
>> to get rid of data duplication and back and forth addr<->mr conversion.
>>
>>> For now, let's just drop vhost_backend_can_merge().
>>>
>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>
>> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>>
>>> ---
>>> hw/virtio/vhost-user.c | 14 --------------
>>> hw/virtio/vhost-vdpa.c | 1 -
>>> hw/virtio/vhost.c | 6 +-----
>>> include/hw/virtio/vhost-backend.h | 4 ----
>>> 4 files changed, 1 insertion(+), 24 deletions(-)
>>>
>>> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
>>> index e68daa35d4..4bfaf559a7 100644
>>> --- a/hw/virtio/vhost-user.c
>>> +++ b/hw/virtio/vhost-user.c
>>> @@ -2195,19 +2195,6 @@ static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
>>> return -ENOTSUP;
>>> }
>>>
>>> -static bool vhost_user_can_merge(struct vhost_dev *dev,
>>> - uint64_t start1, uint64_t size1,
>>> - uint64_t start2, uint64_t size2)
>>> -{
>>> - ram_addr_t offset;
>>> - int mfd, rfd;
>>> -
>>> - (void)vhost_user_get_mr_data(start1, &offset, &mfd);
>>> - (void)vhost_user_get_mr_data(start2, &offset, &rfd);
>>> -
>>> - return mfd == rfd;
>>> -}
>>> -
>>> static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
>>> {
>>> VhostUserMsg msg;
>>> @@ -2704,7 +2691,6 @@ const VhostOps user_ops = {
>>> .vhost_set_vring_enable = vhost_user_set_vring_enable,
>>> .vhost_requires_shm_log = vhost_user_requires_shm_log,
>>> .vhost_migration_done = vhost_user_migration_done,
>>> - .vhost_backend_can_merge = vhost_user_can_merge,
>>> .vhost_net_set_mtu = vhost_user_net_set_mtu,
>>> .vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
>>> .vhost_send_device_iotlb_msg = vhost_user_send_device_iotlb_msg,
>>> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
>>> index 542e003101..9ab7bc8718 100644
>>> --- a/hw/virtio/vhost-vdpa.c
>>> +++ b/hw/virtio/vhost-vdpa.c
>>> @@ -1317,7 +1317,6 @@ const VhostOps vdpa_ops = {
>>> .vhost_set_config = vhost_vdpa_set_config,
>>> .vhost_requires_shm_log = NULL,
>>> .vhost_migration_done = NULL,
>>> - .vhost_backend_can_merge = NULL,
>>> .vhost_net_set_mtu = NULL,
>>> .vhost_set_iotlb_callback = NULL,
>>> .vhost_send_device_iotlb_msg = NULL,
>>> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
>>> index b7fb960fa9..9d8662aa98 100644
>>> --- a/hw/virtio/vhost.c
>>> +++ b/hw/virtio/vhost.c
>>> @@ -733,11 +733,7 @@ static void vhost_region_add_section(struct vhost_dev *dev,
>>> size_t offset = mrs_gpa - prev_gpa_start;
>>>
>>> if (prev_host_start + offset == mrs_host &&
>>> - section->mr == prev_sec->mr &&
>>> - (!dev->vhost_ops->vhost_backend_can_merge ||
>>> - dev->vhost_ops->vhost_backend_can_merge(dev,
>
> another question, can it relly happen, i.e. having 2 abut memory sections
> with the same memory region, is yes then when/why?
Unfortunately yet, because vhost relies on some hacks (sorry, but
that's what it is) to make huge pages work. The following commit
contains some details:
commit 76525114736e8f669766e69b715fa59ce8648aae
Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Date: Thu Jan 16 20:24:14 2020 +0000
vhost: Only align sections for vhost-user
I added hugepage alignment code in c1ece84e7c9 to deal with
vhost-user + postcopy which needs aligned pages when using userfault.
However, on x86 the lower 2MB of address space tends to be shotgun'd
with small fragments around the 512-640k range - e.g. video RAM, and
with HyperV synic pages tend to sit around there - again splitting
it up. The alignment code complains with a 'Section rounded to ...'
error and gives up.
Otherwise it wouldn't be needed, because flatview simplification code already
merges what's reasonable.
[I'll reply to you pother mail regarding that shortly]
--
Thanks,
David / dhildenb
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