linux-kernel - Re: [PATCH v7 05/12] KVM: guest_memfd: Add flag to remove from direct map

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Message-ID: <DDWOP8GKHESP.2EOY2HGM9RXHU@google.com>
Date: Fri, 31 Oct 2025 17:30:12 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: "Roy, Patrick" <roypat@...zon.co.uk>
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Subject: Re: [PATCH v7 05/12] KVM: guest_memfd: Add flag to remove from direct map

On Wed Sep 24, 2025 at 3:22 PM UTC, Patrick Roy wrote:
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 1d0585616aa3..73a15cade54a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -731,6 +731,12 @@ static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
>  bool kvm_arch_supports_gmem_mmap(struct kvm *kvm);
>  #endif
>  
> +#ifdef CONFIG_KVM_GUEST_MEMFD
> +#ifndef kvm_arch_gmem_supports_no_direct_map
> +#define kvm_arch_gmem_supports_no_direct_map can_set_direct_map
> +#endif
> +#endif /* CONFIG_KVM_GUEST_MEMFD */

The test robot seems happy so I think I'm probably mistaken here, but
AFAICS can_set_direct_map only exists when ARCH_HAS_SET_DIRECT_MAP,
which powerpc doesn't set.

If this is indeed an issue I think it can be fixed by just defining
can_set_direct_map() to false when !ARCH_HAS_SET_DIRECT_MAP.