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Message-ID: <04398f4e-6098-4559-9604-b9810753801e@intel.com>
Date: Fri, 1 Mar 2024 10:53:22 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Dongli Zhang <dongli.zhang@...cle.com>, <kvm@...r.kernel.org>
CC: <pbonzini@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] KVM: use KVM_HVA_ERR_BAD to check bad hva
On 1/03/2024 10:25 am, Dongli Zhang wrote:
> Replace PAGE_OFFSET with KVM_HVA_ERR_BAD, to facilitate the cscope when
> looking for where KVM_HVA_ERR_BAD is used.
>
> Every time I use cscope to query the functions that are impacted by the
> return value (KVM_HVA_ERR_BAD) of __gfn_to_hva_many(), I may miss
> kvm_is_error_hva().
I am not sure "to facilitate cscope" could be a justification to do some
code change in the kernel.
>
> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
> ---
> include/linux/kvm_host.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7e7fd25b09b3..4dc0300e7766 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -143,7 +143,7 @@ static inline bool is_noslot_pfn(kvm_pfn_t pfn)
>
> static inline bool kvm_is_error_hva(unsigned long addr)
> {
> - return addr >= PAGE_OFFSET;
> + return addr >= KVM_HVA_ERR_BAD;
> }
>
> #endif
Also, IIUC the KVM_HVA_ERR_BAD _theoretically_ can be any random value
that can make kvm_is_error_hva() return false, while kvm_is_error_hva()
must catch all error HVAs.
E.g., if we ever change KVM_HVA_ERR_BAD to use any other value (although
I don't see why this could ever happen), then using KVM_HVA_ERR_BAD in
kvm_is_error_hva() would be broken.
In other words, it seems to me we should just use PAGE_OFFSET in
kvm_is_error_hva().
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