Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Manwaring, Derek
On 2024-05-13 13:36-0700, Sean Christopherson wrote: > Hmm, a slightly crazy idea (ok, maybe wildly crazy) would be to support > mapping > all of guest_memfd into kernel address space, but as USER=1 mappings.  I.e. > don't > require a carve-out from userspace, but do require CLAC/STAC when

Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Sean Christopherson
On Mon, May 13, 2024, James Gowans wrote: > On Mon, 2024-05-13 at 10:09 -0700, Sean Christopherson wrote: > > On Mon, May 13, 2024, James Gowans wrote: > > > On Mon, 2024-05-13 at 08:39 -0700, Sean Christopherson wrote: > > > > > Sean, you mentioned that you envision guest_memfd also supporting >

Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Gowans, James
On Mon, 2024-05-13 at 10:09 -0700, Sean Christopherson wrote: > On Mon, May 13, 2024, James Gowans wrote: > > On Mon, 2024-05-13 at 08:39 -0700, Sean Christopherson wrote: > > > > Sean, you mentioned that you envision guest_memfd also supporting > > > > non-CoCo VMs. > > > > Do you have some

Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Sean Christopherson
On Mon, May 13, 2024, James Gowans wrote: > On Mon, 2024-05-13 at 08:39 -0700, Sean Christopherson wrote: > > > Sean, you mentioned that you envision guest_memfd also supporting > > > non-CoCo VMs. > > > Do you have some thoughts about how to make the above cases work in the > > > guest_memfd

Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Gowans, James
On Mon, 2024-05-13 at 08:39 -0700, Sean Christopherson wrote: > > Sean, you mentioned that you envision guest_memfd also supporting non-CoCo > > VMs. > > Do you have some thoughts about how to make the above cases work in the > > guest_memfd context? > > Yes.  The hand-wavy plan is to allow

Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Sean Christopherson
On Mon, May 13, 2024, Patrick Roy wrote: > For non-CoCo VMs, where memory is not encrypted, and the threat model assumes > a > trusted host userspace, we would like to avoid changing the VM model so > completely. If we adopt CoCo’s approaches where KVM / Userspace touches guest > memory we would

Re: Unmapping KVM Guest Memory from Host Kernel

2024-05-13 Thread Patrick Roy
Hi all, On 3/9/24 11:14, Mike Rapoport wrote: >>> >>> With this in mind, what’s the best way to solve getting guest RAM out of >>> >>> the direct map? Is memfd_secret integration with KVM the way to go, or >>> >>> should we build a solution on top of guest_memfd, for example via some >>> >>>

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-18 Thread Brendan Jackman
On Fri, 8 Mar 2024 at 18:36, David Matlack wrote: > I'm not sure if ASI provides a solution to the problem James is trying > to solve. ASI creates a separate "restricted" address spaces where, yes, > guest memory can be not mapped. But any access to guest memory is > still allowed. An access

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-14 Thread Manwaring, Derek
On Fri, 8 Mar 2024 15:22:50 -0800, Sean Christopherson wrote: > On Fri, Mar 08, 2024, James Gowans wrote: > > We are also aware of ongoing work on guest_memfd. The current > > implementation unmaps guest memory from VMM address space, but leaves it > > in the kernel’s direct map. We’re not looking

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-11 Thread Fuad Tabba
On Mon, Mar 11, 2024 at 9:26 AM Fuad Tabba wrote: > > Hi, > > On Fri, Mar 8, 2024 at 9:05 PM Manwaring, Derek wrote: > > > > On 2024-03-08 at 10:46-0700, David Woodhouse wrote: > > > On Fri, 2024-03-08 at 09:35 -0800, David Matlack wrote: > > > > I think what James is looking for (and what we

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-11 Thread Fuad Tabba
Hi, On Fri, Mar 8, 2024 at 9:05 PM Manwaring, Derek wrote: > > On 2024-03-08 at 10:46-0700, David Woodhouse wrote: > > On Fri, 2024-03-08 at 09:35 -0800, David Matlack wrote: > > > I think what James is looking for (and what we are also interested > > > in), is _eliminating_ the ability to

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-09 Thread Mike Rapoport
On Fri, Mar 08, 2024 at 03:22:50PM -0800, Sean Christopherson wrote: > On Fri, Mar 08, 2024, James Gowans wrote: > > However, memfd_secret doesn’t work out the box for KVM guest memory; the > > main reason seems to be that the GUP path is intentionally disabled for > > memfd_secret, so if we use a

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread Matthew Wilcox
On Fri, Mar 08, 2024 at 03:50:05PM +, Gowans, James wrote: > Currently when using anonymous memory for KVM guest RAM, the memory all > remains mapped into the kernel direct map. We are looking at options to > get KVM guest memory out of the kernel’s direct map as a principled > approach to

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread Manwaring, Derek
On 2024-03-08 10:36-0700, David Matlack wrote: > On Fri, Mar 8, 2024 at 8:25 AM Brendan Jackman wrote: > > On Fri, 8 Mar 2024 at 16:50, Gowans, James wrote: > > > Our goal is to more completely address the class of issues whose leak > > > origin is categorized as "Mapped memory" [1]. > > > > Did

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread Sean Christopherson
On Fri, Mar 08, 2024, James Gowans wrote: > However, memfd_secret doesn’t work out the box for KVM guest memory; the > main reason seems to be that the GUP path is intentionally disabled for > memfd_secret, so if we use a memfd_secret backed VMA for a memslot then > KVM is not able to fault the

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread David Matlack
On Fri, Mar 8, 2024 at 8:25 AM Brendan Jackman wrote: > > Hi James > > On Fri, 8 Mar 2024 at 16:50, Gowans, James wrote: > > Our goal is to more completely address the class of issues whose leak > > origin is categorized as "Mapped memory" [1]. > > Did you forget a link below? I'm interested in

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread Manwaring, Derek
On 2024-03-08 at 10:46-0700, David Woodhouse wrote: > On Fri, 2024-03-08 at 09:35 -0800, David Matlack wrote: > > I think what James is looking for (and what we are also interested > > in), is _eliminating_ the ability to access guest memory from the > > direct map entirely. And in general,

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread Sean Christopherson
On Fri, Mar 08, 2024, David Woodhouse wrote: > On Fri, 2024-03-08 at 09:35 -0800, David Matlack wrote: > > I think what James is looking for (and what we are also interested > > in), is _eliminating_ the ability to access guest memory from the > > direct map entirely. And in general, eliminate the

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread David Woodhouse
On Fri, 2024-03-08 at 09:35 -0800, David Matlack wrote: > I think what James is looking for (and what we are also interested > in), is _eliminating_ the ability to access guest memory from the > direct map entirely. And in general, eliminate the ability to access > guest memory in as many ways as

Re: Unmapping KVM Guest Memory from Host Kernel

2024-03-08 Thread Brendan Jackman
Hi James On Fri, 8 Mar 2024 at 16:50, Gowans, James wrote: > Our goal is to more completely address the class of issues whose leak > origin is categorized as "Mapped memory" [1]. Did you forget a link below? I'm interested in hearing about that categorisation. > ... what’s the best way to