linux-kernel - Re: [PATCH 09/15] KVM: selftests: Move per-VM GPA into perf_test

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Date:   Thu, 11 Feb 2021 14:12:52 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Cc:     kvm <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Yanan Wang <wangyanan55@...wei.com>,
        Andrew Jones <drjones@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Aaron Lewis <aaronlewis@...gle.com>
Subject: Re: [PATCH 09/15] KVM: selftests: Move per-VM GPA into perf_test_args

On 11/02/21 02:56, Sean Christopherson wrote:
>>> +       pta->gpa = (vm_get_max_gfn(vm) - guest_num_pages) * pta->guest_page_size;
>>> +       pta->gpa &= ~(pta->host_page_size - 1);
>> Also not related to this patch, but another case for align.
>>
>>>          if (backing_src == VM_MEM_SRC_ANONYMOUS_THP ||
>>>              backing_src == VM_MEM_SRC_ANONYMOUS_HUGETLB)
>>> -               guest_test_phys_mem &= ~(KVM_UTIL_HUGEPAGE_ALIGNMENT - 1);
>>> -
>>> +               pta->gpa &= ~(KVM_UTIL_HUGEPAGE_ALIGNMENT - 1);
>> also align
>>
>>>   #ifdef __s390x__
>>>          /* Align to 1M (segment size) */
>>> -       guest_test_phys_mem &= ~((1 << 20) - 1);
>>> +       pta->gpa &= ~((1 << 20) - 1);
>> And here again (oof)
> 
> Yep, I'll fix all these and the align() comment in v2.

This is not exactly align in fact; it is x & ~y rather than (x + y) & 
~y.  Are you going to introduce a round-down macro or is it a bug?  (I 
am lazy...).

Paolo