linux-kernel - Re: [PATCH v10 2/9] KVM: Introduce per-page memory attributes

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Message-ID: <20230209072529.GB4175971@ls.amr.corp.intel.com>
Date:   Wed, 8 Feb 2023 23:25:29 -0800
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, qemu-devel@...gnu.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
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        Naoya Horiguchi <naoya.horiguchi@....com>,
        Miaohe Lin <linmiaohe@...wei.com>, x86@...nel.org,
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        Quentin Perret <qperret@...gle.com>, tabba@...gle.com,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        wei.w.wang@...el.com, isaku.yamahata@...il.com
Subject: Re: [PATCH v10 2/9] KVM: Introduce per-page memory attributes

On Fri, Dec 02, 2022 at 02:13:40PM +0800,
Chao Peng <chao.p.peng@...ux.intel.com> wrote:

> +static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> +					   struct kvm_memory_attributes *attrs)
> +{
> +	gfn_t start, end;
> +	unsigned long i;
> +	void *entry;
> +	u64 supported_attrs = kvm_supported_mem_attributes(kvm);
> +
> +	/* flags is currently not used. */
> +	if (attrs->flags)
> +		return -EINVAL;
> +	if (attrs->attributes & ~supported_attrs)
> +		return -EINVAL;
> +	if (attrs->size == 0 || attrs->address + attrs->size < attrs->address)
> +		return -EINVAL;
> +	if (!PAGE_ALIGNED(attrs->address) || !PAGE_ALIGNED(attrs->size))
> +		return -EINVAL;
> +
> +	start = attrs->address >> PAGE_SHIFT;
> +	end = (attrs->address + attrs->size - 1 + PAGE_SIZE) >> PAGE_SHIFT;
> +
> +	entry = attrs->attributes ? xa_mk_value(attrs->attributes) : NULL;
> +
> +	mutex_lock(&kvm->lock);
> +	for (i = start; i < end; i++)
> +		if (xa_err(xa_store(&kvm->mem_attr_array, i, entry,
> +				    GFP_KERNEL_ACCOUNT)))
> +			break;
> +	mutex_unlock(&kvm->lock);
> +
> +	attrs->address = i << PAGE_SHIFT;
> +	attrs->size = (end - i) << PAGE_SHIFT;
> +
> +	return 0;
> +}
> +#endif /* CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES */
> +

If memslot isn't private, it should return error if private attribute is set.
Something like following check is needed.

+       if (attrs->flags & KVM_MEM_PRIVATE) {
+               /* non-private memory slot doesn't allow KVM_MEM_PRIVATE */
+               for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
+                       struct kvm_memslot_iter iter;
+                       struct kvm_memslots *slots;
+
+                       slots = __kvm_memslots(kvm, i);
+                       kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
+                               if (!kvm_slot_can_be_private(iter.slot)) {
+                                       mutex_unlock(&kvm->slots_lock);
+                                       return -EINVAL;
+                               }
+                       }
+               }
+       }
+


-- 
Isaku Yamahata <isaku.yamahata@...il.com>