Re: [PATCH 0/7] KVM: arm64: Hypervisor stack enhancements

[Marc Zyngier]

On Thu, 10 Feb 2022 22:41:41 +0000,
Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote:
> 
> This series is based on v5.17-rc3 and adds the following stack features to
> the KVM nVHE hypervisor:
> 
> == Hyp Stack Guard Pages ==
> 
> Based on the technique used by arm64 VMAP_STACK to detect overflow.
> i.e. the stack is aligned to twice its size which ensure that the 
> 'stack shift' bit of any valid SP is 0. The 'stack shift' bit can be
> tested in the exception entry to detect overflow without corrupting GPRs.

Having quickly parsed the code, this seems to only be effective for
pKVM and the EL2-allocated stack. Is there any technical reason not to
implement this for the much more common case of 'classic' KVM in nVHE
mode?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.