linux-kernel - Re: [PATCH] kvm: selftests: Fix cut-off of addr

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Date:   Thu, 14 Apr 2022 16:14:22 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Peter Xu <peterx@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ben Gardon <bgardon@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH] kvm: selftests: Fix cut-off of addr_gva2gpa lookup

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