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Date:   Thu, 14 Apr 2022 16:14:22 +0200
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Subject: Re: [PATCH] kvm: selftests: Fix cut-off of addr_gva2gpa lookup
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To:     Sean Christopherson <seanjc@google.com>,
        Peter Xu <peterx@redhat.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ben Gardon <bgardon@google.com>,
        David Matlack <dmatlack@google.com>,
        Andrew Jones <drjones@redhat.com>
References: <20220414010703.72683-1-peterx@redhat.com>
 <Ylgn/Jw+FMIFqqc0@google.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
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On 4/14/22 15:56, Sean Christopherson wrote:
>> -	return (pte[index[0]].pfn * vm->page_size) + (gva & 0xfffu);
>> +	return ((vm_paddr_t)pte[index[0]].pfn * vm->page_size) + (gva & 0xfffu);
> This is but one of many paths that can get burned by pfn being 40 bits.  The
> most backport friendly fix is probably to add a pfn=>gpa helper and use that to
> place the myriad "pfn * vm->page_size" instances.
> 
> For a true long term solution, my vote is to do away with the bit field struct
> and use #define'd masks and whatnot.

Yes, bitfields larger than 32 bits are a mess.

Paolo