Re: [PATCH] KVM: arm64: Properly return allocated EL2 VA from hyp_alloc_private_va_range()

[Vincent Donnefort <vdonnefort@google.com>]

On Tue, Aug 29, 2023 at 09:03:05AM +0100, Vincent Donnefort wrote:
> On Mon, Aug 28, 2023 at 04:31:21PM +0100, Marc Zyngier wrote:
> > Marek reports that his RPi4 spits out a warning at boot time,
> > right at the point where the GICv2 virtual CPU interface gets
> > mapped.
> > 
> > Upon investigation, it seems that we never return the allocated
> > VA and use whatever was on the stack at this point. Yes, this
> > is good stuff, and Marek was pretty lucky that he ended-up with
> > a VA that intersected with something that was already mapped.
> > 
> > On my setup, this random value is plausible enough for the mapping
> > to take place. Who knows what happens...
> > 
> > Cc: Vincent Donnefort <vdonnefort@google.com>
> > Fixes: f156a7d13fc3 ("KVM: arm64: Remove size-order align in the nVHE hyp private VA range")
> > Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Link: https://lore.kernel.org/r/79b0ad6e-0c2a-f777-d504-e40e8123d81d@samsung.com
> 
> Having a hard time reproducing the issue, but clearly that set is missing from
> the original patch!
> 
> Sorry about that extra work.

Reviewed-by: Vincent Donnefort <vdonnefort@google.com>

> 
> > ---
> >  arch/arm64/kvm/mmu.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 11c1d786c506..50be51cc40cc 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -652,6 +652,9 @@ int hyp_alloc_private_va_range(size_t size, unsigned long *haddr)
> >  
> >  	mutex_unlock(&kvm_hyp_pgd_mutex);
> >  
> > +	if (!ret)
> > +		*haddr = base;
> > +
> >  	return ret;
> >  }
> >  
> > -- 
> > 2.34.1
> >