From: Sean Christopherson <seanjc@google.com>
To: "wangyanan (Y)" <wangyanan55@huawei.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Ben Gardon <bgardon@google.com>,
Andrew Jones <drjones@redhat.com>, Peter Xu <peterx@redhat.com>,
Aaron Lewis <aaronlewis@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 04/15] KVM: selftests: Force stronger HVA alignment (1gb) for hugepages
Date: Fri, 12 Mar 2021 16:26:36 -0800 [thread overview]
Message-ID: <YEwGvHe+wcaEG0W8@google.com> (raw)
In-Reply-To: <9a870968-f381-3e0b-2840-62b7c2b2e032@huawei.com>
On Thu, Feb 25, 2021, wangyanan (Y) wrote:
>
> On 2021/2/11 7:06, Sean Christopherson wrote:
> > Align the HVA for hugepage memslots to 1gb, as opposed to incorrectly
> > assuming all architectures' hugepages are 512*page_size.
> >
> > For x86, multiplying by 512 is correct, but only for 2mb pages, e.g.
> > systems that support 1gb pages will never be able to use them for mapping
> > guest memory, and thus those flows will not be exercised.
> >
> > For arm64, powerpc, and s390 (and mips?), hardcoding the multiplier to
> > 512 is either flat out wrong, or at best correct only in certain
> > configurations.
> >
> > Hardcoding the _alignment_ to 1gb is a compromise between correctness and
> > simplicity. Due to the myriad flavors of hugepages across architectures,
> > attempting to enumerate the exact hugepage size is difficult, and likely
> > requires probing the kernel.
> >
> > But, there is no need for precision since a stronger alignment will not
> > prevent creating a smaller hugepage. For all but the most extreme cases,
> > e.g. arm64's 16gb contiguous PMDs, aligning to 1gb is sufficient to allow
> > KVM to back the guest with hugepages.
> I have implemented a helper get_backing_src_pagesz() to get granularity of
> different
> backing src types (anonymous/thp/hugetlb) which is suitable for different
> architectures.
> See:
> https://lore.kernel.org/lkml/20210225055940.18748-6-wangyanan55@huawei.com/
> if it looks fine for you, maybe we can use the accurate page sizes for
> GPA/HVA alignment:).
Works for me. I'll probably just wait until your series is queued to send v2.
Thanks again!
next prev parent reply other threads:[~2021-03-13 0:30 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 23:06 [PATCH 00/15] VM: selftests: Hugepage fixes and cleanups Sean Christopherson
2021-02-10 23:06 ` [PATCH 01/15] KVM: selftests: Explicitly state indicies for vm_guest_mode_params array Sean Christopherson
2021-02-11 0:50 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 02/15] KVM: selftests: Expose align() helpers to tests Sean Christopherson
2021-02-11 0:49 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 03/15] KVM: selftests: Align HVA for HugeTLB-backed memslots Sean Christopherson
2021-02-11 0:52 ` Ben Gardon
2021-02-25 7:40 ` wangyanan (Y)
2021-03-13 0:17 ` Sean Christopherson
2021-02-10 23:06 ` [PATCH 04/15] KVM: selftests: Force stronger HVA alignment (1gb) for hugepages Sean Christopherson
2021-02-25 7:57 ` wangyanan (Y)
2021-03-13 0:26 ` Sean Christopherson [this message]
2021-02-10 23:06 ` [PATCH 05/15] KVM: selftests: Require GPA to be aligned when backed by hugepages Sean Christopherson
2021-02-11 1:01 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 06/15] KVM: selftests: Use shorthand local var to access struct perf_tests_args Sean Christopherson
2021-02-11 1:09 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 07/15] KVM: selftests: Capture per-vCPU GPA in perf_test_vcpu_args Sean Christopherson
2021-02-11 1:24 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 08/15] KVM: selftests: Use perf util's per-vCPU GPA/pages in demand paging test Sean Christopherson
2021-02-11 1:23 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 09/15] KVM: selftests: Move per-VM GPA into perf_test_args Sean Christopherson
2021-02-11 1:22 ` Ben Gardon
2021-02-11 1:56 ` Sean Christopherson
2021-02-11 13:12 ` Paolo Bonzini
2021-02-11 15:57 ` Sean Christopherson
2021-02-11 17:33 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 10/15] KVM: selftests: Remove perf_test_args.host_page_size Sean Christopherson
2021-02-11 1:26 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 11/15] KVM: selftests: Create VM with adjusted number of guest pages for perf tests Sean Christopherson
2021-02-11 1:32 ` Ben Gardon
2021-02-10 23:06 ` [PATCH 12/15] KVM: selftests: Fill per-vCPU struct during "perf_test" VM creation Sean Christopherson
2021-02-10 23:06 ` [PATCH 13/15] KVM: selftests: Sync perf_test_args to guest during " Sean Christopherson
2021-02-10 23:06 ` [PATCH 14/15] KVM: selftests: Track size of per-VM memslot in perf_test_args Sean Christopherson
2021-02-10 23:06 ` [PATCH 15/15] KVM: selftests: Get rid of gorilla math in memslots modification test Sean Christopherson
2021-02-11 11:58 ` [PATCH 00/15] VM: selftests: Hugepage fixes and cleanups Andrew Jones
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