d**e
发帖数: 863 | 1 How is virtualization supported by CPU design?
I mean, what extra must be done so that a particular
CPU chip supports virtualization? |
S*A
发帖数: 7142 | 2 No must. The early x86 CPU can still run virtualization
using binary translations. VMware does that.
The recent CPU change make virtualization easier in a
sense. Not as easy as most people thing though.
【在 d**e 的大作中提到】
: How is virtualization supported by CPU design?
: I mean, what extra must be done so that a particular
: CPU chip supports virtualization?
|
d**e
发帖数: 863 | 3
Thank you, actually I asked one question before,
http://www.mitbbs.com/article_t0/Linux/31257399.html
as I read a recent magazine article, ARM
defended its decision to not support virtualization.
That makes me wonder what more are needed to support virtualization.
【在 S*A 的大作中提到】
: No must. The early x86 CPU can still run virtualization
: using binary translations. VMware does that.
: The recent CPU change make virtualization easier in a
: sense. Not as easy as most people thing though.
|
N****w
发帖数: 21578 | 4 it was not binary translation.
only pearlpc is, which runs PowerPC instructions on x86, and very slow.
virtualization is possible after 386, with those "int xx" and io traps
new "virtualized" CPU just add more support to make virtualization easier
and faster.
【在 S*A 的大作中提到】
: No must. The early x86 CPU can still run virtualization
: using binary translations. VMware does that.
: The recent CPU change make virtualization easier in a
: sense. Not as easy as most people thing though.
|
S*A
发帖数: 7142 | 5
Where do you get that? That is obvious wrong.
Check out this wiki page:
http://en.wikipedia.org/wiki/Full_virtualization
And check out the vmware binary translate patents.
No, int xx can only handle user space code. That helps to write kernel.
But it does not help to write full virtualization. A lot of x86
instructions reveal CPU internal stage. e.g. SLDT can run on ring 3.
Using int xx can't help you ritualize the windows kernel for example.
If you put the whole windows kenrel in ring 3. Windows SLDT will get
reveal the existence of hypervisor.
【在 N****w 的大作中提到】
: it was not binary translation.
: only pearlpc is, which runs PowerPC instructions on x86, and very slow.
: virtualization is possible after 386, with those "int xx" and io traps
: new "virtualized" CPU just add more support to make virtualization easier
: and faster.
|
N****w
发帖数: 21578 | 6 vmware 最早出来时，CPU 都没有现在说的 virtualization 功能
特权指令全都 trap 到host OS 里特别处理
后来为了提高效率，Intel， AMD 给 CPU 加了些功能
【在 S*A 的大作中提到】
:
: Where do you get that? That is obvious wrong.
: Check out this wiki page:
: http://en.wikipedia.org/wiki/Full_virtualization
: And check out the vmware binary translate patents.
: No, int xx can only handle user space code. That helps to write kernel.
: But it does not help to write full virtualization. A lot of x86
: instructions reveal CPU internal stage. e.g. SLDT can run on ring 3.
: Using int xx can't help you ritualize the windows kernel for example.
: If you put the whole windows kenrel in ring 3. Windows SLDT will get
|
S*A
发帖数: 7142 | 7
Wrong, "trap" into VMM. Not host OS. Only switch to host OS
when it is needed. Switch to host is call a world switch in
ESX. It is very expensive. Not some thing you want to do for
privilege instructions.
It is using binary translation to trap privilege instructions,
not "int XX" stuff. The early version of VMware use binary
translation very heavily.
【在 N****w 的大作中提到】
: vmware 最早出来时，CPU 都没有现在说的 virtualization 功能
: 特权指令全都 trap 到host OS 里特别处理
: 后来为了提高效率，Intel， AMD 给 CPU 加了些功能
|
f****a
发帖数: 4708 | 8 新加的指令有VMSAVE/VMRESTORE，大大减少了world switch的时间。
而且提供了特权指令的统一的Trap。
后来又增加了nested paging，使world switch后TLB miss大大减少。
【在 S*A 的大作中提到】
:
: Wrong, "trap" into VMM. Not host OS. Only switch to host OS
: when it is needed. Switch to host is call a world switch in
: ESX. It is very expensive. Not some thing you want to do for
: privilege instructions.
: It is using binary translation to trap privilege instructions,
: not "int XX" stuff. The early version of VMware use binary
: translation very heavily.
|
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