linux-kernel - Re: [PATCH 3/4] KVM: arm64: Fix address check for memory slot

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Message-ID: <be57b9fb-89c4-9c32-f273-9f4bbe973b00@huawei.com>
Date:   Mon, 15 Mar 2021 15:33:39 +0800
From:   Keqian Zhu <zhukeqian1@...wei.com>
To:     Gavin Shan <gshan@...hat.com>, <kvmarm@...ts.cs.columbia.edu>
CC:     <maz@...nel.org>, <will@...nel.org>,
        <linux-kernel@...r.kernel.org>, <shan.gavin@...il.com>
Subject: Re: [PATCH 3/4] KVM: arm64: Fix address check for memory slot

Hi Gavin,

FYI, this has been fixed by Marc in commit 262b003d059c.

Thanks,
Keqian

On 2021/3/15 12:18, Gavin Shan wrote:
> The last (IPA) page can't be specified when a new memory slot is
> added. The error -EFAULT is returned when the memory slot is added
> with the following parameters for the VM, which has 40-bits IPA
> limit. The host has 4KB base page size. It's not correct because
> the last (IPA) page is still usable.
> 
>    struct kvm_userspace_memory_region {
>       __u32 slot;               /* 1            */
>       __u32 flags;              /* 0            */
>       __u64 guest_phys_addr;    /* 0xfffffff000 */
>       __u64 memory_size;        /* 0x1000       */
>       __u64 userspace_addr;
>    };
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  arch/arm64/kvm/mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 286b603ed0d3..a5a8ade9fde4 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1313,7 +1313,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	 * Prevent userspace from creating a memory region outside of the IPA
>  	 * space addressable by the KVM guest IPA space.
>  	 */
> -	if (memslot->base_gfn + memslot->npages >=
> +	if (memslot->base_gfn + memslot->npages >
>  	    (kvm_phys_size(kvm) >> PAGE_SHIFT))
>  		return -EFAULT;
>  
>