linux-kernel - Re: [PATCH v9 6/6] KVM: x86/mmu: Handle non-refcounted pages

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Date:   Thu, 21 Sep 2023 23:04:33 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     David Stevens <stevensd@...omium.org>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v9 6/6] KVM: x86/mmu: Handle non-refcounted pages

On 9/19/23 05:31, David Stevens wrote:
> On Mon, Sep 18, 2023 at 6:58 PM Dmitry Osipenko
> <dmitry.osipenko@...labora.com> wrote:
>>
>> On 9/11/23 05:16, David Stevens wrote:
>>> From: David Stevens <stevensd@...omium.org>
>>>
>>> Handle non-refcounted pages in __kvm_faultin_pfn. This allows the host
>>> to map memory into the guest that is backed by non-refcounted struct
>>> pages - for example, the tail pages of higher order non-compound pages
>>> allocated by the amdgpu driver via ttm_pool_alloc_page.
>>>
>>> The bulk of this change is tracking the is_refcounted_page flag so that
>>> non-refcounted pages don't trigger page_count() == 0 warnings. This is
>>> done by storing the flag in an unused bit in the sptes. There are no
>>> bits available in PAE SPTEs, so non-refcounted pages can only be handled
>>> on TDP and x86-64.
>>>
>>> Signed-off-by: David Stevens <stevensd@...omium.org>
>>> ---
>>>  arch/x86/kvm/mmu/mmu.c          | 52 +++++++++++++++++++++++----------
>>>  arch/x86/kvm/mmu/mmu_internal.h |  1 +
>>>  arch/x86/kvm/mmu/paging_tmpl.h  |  8 +++--
>>>  arch/x86/kvm/mmu/spte.c         |  4 ++-
>>>  arch/x86/kvm/mmu/spte.h         | 12 +++++++-
>>>  arch/x86/kvm/mmu/tdp_mmu.c      | 22 ++++++++------
>>>  include/linux/kvm_host.h        |  3 ++
>>>  virt/kvm/kvm_main.c             |  6 ++--
>>>  8 files changed, 76 insertions(+), 32 deletions(-)
>>
>> Could you please tell which kernel tree you used for the base of this
>> series? This patch #6 doesn't apply cleanly to stable/mainline/next/kvm
>>
>> error: sha1 information is lacking or useless (arch/x86/kvm/mmu/mmu.c).
>> error: could not build fake ancestor
> 
> This series is based on the kvm next branch (i.e.
> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=next). The
> specific hash is d011151616e73de20c139580b73fa4c7042bd861.

Thanks, this tag works

-- 
Best regards,
Dmitry