linux-kernel - Re: [PATCH RFC v7 06/64] KVM: x86: Add platform hooks for private memory invalidations

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Message-ID: <Y67RO+YnQYSX4mvN@zn.tnic>
Date:   Fri, 30 Dec 2022 12:53:31 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Michael Roth <michael.roth@....com>
Cc:     kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
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        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        luto@...nel.org, dave.hansen@...ux.intel.com, slp@...hat.com,
        pgonda@...gle.com, peterz@...radead.org,
        srinivas.pandruvada@...ux.intel.com, rientjes@...gle.com,
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        alpergun@...gle.com, dgilbert@...hat.com, jarkko@...nel.org,
        ashish.kalra@....com, harald@...fian.com
Subject: Re: [PATCH RFC v7 06/64] KVM: x86: Add platform hooks for private
 memory invalidations

On Wed, Dec 14, 2022 at 01:39:58PM -0600, Michael Roth wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index a0c41d391547..2713632e5061 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -7183,3 +7183,8 @@ void kvm_arch_set_memory_attributes(struct kvm *kvm,
>  		kvm_update_lpage_private_shared_mixed(kvm, slot, attrs,
>  						      start, end);
>  }
> +
> +void kvm_arch_invalidate_restricted_mem(struct kvm_memory_slot *slot, gfn_t start, gfn_t end)
> +{
> +	static_call_cond(kvm_x86_invalidate_restricted_mem)(slot, start, end);

Why _cond?

> @@ -258,6 +263,17 @@ void restrictedmem_unregister_notifier(struct file *file,
>  				       struct restrictedmem_notifier *notifier)
>  {
>  	struct restrictedmem_data *data = file->f_mapping->private_data;
> +	struct inode *inode = file_inode(data->memfd);
> +
> +	/* TODO: this will issue notifications to all registered notifiers,

First of all:

verify_comment_style: WARNING: Multi-line comment needs to start text on the second line:
 [+     /* TODO: this will issue notifications to all registered notifiers,]

Then, if you only want to run the callbacks for the one going away only,
why don't you simply do:

        mutex_lock(&data->lock);
        notifier->ops->invalidate_start(notifier, 0, inode->i_size >> PAGE_SHIFT);
        notifier->ops->invalidate_end(notifier, 0, inode->i_size >> PAGE_SHIFT);
        list_del(&notifier->list);
        mutex_unlock(&data->lock);

here?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette