Re: [PATCH v2 3/3] KVM: arm64: Don't replace a valid hyp block mapping with a table

[Vincent Donnefort <vdonnefort@google.com>]

On Fri, Nov 06, 2026 at 05:17:54PM +0000, Xuheng Li wrote:
> Hi Fuad, Vincent,
> 
> On Fri, Nov 06, 2026 at 02:34:55PM +0000, Fuad Tabba wrote:
> > Actually, like Vincent pointed out, why the WARN_ON(). The caller can
> > just handle the error.
> 
> Makes sense, I'll drop the WARN_ON() and just return -EEXIST.
> 
> One thing I noticed: the kernel-doc of kvm_pgtable_hyp_map() says that
> a mapping over an existing one is "rejected with an error and a
> WARN()", and the leaf case in hyp_map_walker_try_leaf() still warns.
> Without the WARN_ON(), the comment would no longer match this case.
> By the same reasoning, should the leaf case's WARN_ON() go too, in a
> separate patch, with the comment reduced to "rejected with an error"?
> 
> Thanks,
> Xuheng

You're going to make me regret my suggestion about removing the WARN_ON() :-) 

Indeed we should probably align the behaviour.

We can indeed drop the WARN_ON() from hyp_map_walker_try_leaf(). The if
(kvm_pte_valid()) you've added should catch this case anyway. 

We can keep the WARN_ON(ctx->level == KVM_PGTABLE_LAST_LEVEL). If hit, that is
an internal error...

I don't know if that warrant a different patch to be honnest... none of that is
fixing any existing bug. But no strong opinion.

-- 
Vincent