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

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Message-ID: <DDYZRG8A99D1.2MYZVGBKJNHJW@google.com>
Date: Mon, 03 Nov 2025 10:35:38 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Mike Rapoport <rppt@...nel.org>, Brendan Jackman <jackmanb@...gle.com>
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Subject: Re: [PATCH v7 05/12] KVM: guest_memfd: Add flag to remove from direct map

On Sat Nov 1, 2025 at 9:39 AM UTC, Mike Rapoport wrote:
> On Fri, Oct 31, 2025 at 05:30:12PM +0000, Brendan Jackman wrote:
>> 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.
>
> We have stubs returning 0 for architectures that don't have
> ARCH_HAS_SET_DIRECT_MAP.

I can't see any such stub for can_set_direct_map() specifically?

(But again, the bot seems happy, so I still suspect I'm wrong somehow or
other).