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SubjectRe: [RFC 00/11] KVM, EFI, arm64: EFI Runtime Services Sandboxing
On 25 August 2017 at 01:31, Florent Revest <> wrote:
> Hi,
> This series implements a mechanism to sandbox EFI Runtime Services on arm64.
> It can be enabled with CONFIG_EFI_SANDBOX. At boot it spawns an internal KVM
> virtual machine that is ran everytime an EFI Runtime Service is called. This
> limits the possible security and stability impact of EFI runtime on the kernel.
> The patch set is split as follow:
> - Patches 1 and 2: Give more control over HVC handling to KVM
> - Patches 3 to 6: Introduce the concept of KVM "internal VMs"
> - Patches 7 to 9: Reorder KVM and EFI initialization on ARM
> - Patch 10: Introduces the EFI sandboxing VM and wrappers
> - Patch 11: Workarounds some EFI Runtime Services relying on EL3
> The sandboxing has been tested to work reliably (rtc and efivars) on a
> SoftIron OverDrive 1000 box and on a ARMv8.3 model with VHE enabled. Normal
> userspace KVM instance have also been tested to still work correctly.
> Those patches apply cleanly on the Linus' v4.13-rc6 tag and have no other
> dependencies.
> Florent Revest (11):
> arm64: Add an SMCCC function IDs header
> KVM: arm64: Return an Unknown ID on unhandled HVC
> KVM: Allow VM lifecycle management without userspace
> KVM, arm, arm64: Offer PAs to IPAs idmapping to internal VMs
> KVM: Expose VM/VCPU creation functions
> KVM, arm64: Expose a VCPU initialization function
> KVM: Allow initialization before the module target
> KVM, arm, arm64: Initialize KVM's core earlier
> EFI, arm, arm64: Enable EFI Runtime Services later
> efi, arm64: Sandbox Runtime Services in a VM
> KVM, arm64: Don't trap internal VMs SMC calls

Hello Florent,

This is really nice work. Thanks for contributing it.

From the EFI side, there are some minor concerns on my part regarding
the calling convention, and the fact that we can no longer invoke
runtime services from a kernel running at EL1, but those all seem
fixable. I will respond to the patches in question in greater detail
at a later time.

In the mean time, Christoffer has raised a number for valid concerns,
and those need to be addressed first before it makes sense to talk
about EFI specifics. I hope you will find more time to invest in this:
I would really love to have this feature upstream.


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