From: Liran Alon <liran.alon@oracle.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Barret Rhoden <brho@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Dan Williams <dan.j.williams@intel.com>,
David Hildenbrand <david@redhat.com>,
Dave Jiang <dave.jiang@intel.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
linux-nvdimm@lists.01.org, x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, jason.zeng@intel.com
Subject: Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files
Date: Fri, 13 Dec 2019 20:08:59 +0200 [thread overview]
Message-ID: <08D4A158-617C-4043-AA85-B12EE8F062B9@oracle.com> (raw)
In-Reply-To: <20191213175031.GC31552@linux.intel.com>
> On 13 Dec 2019, at 19:50, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
>
> On Fri, Dec 13, 2019 at 07:31:55PM +0200, Liran Alon wrote:
>>
>>> On 13 Dec 2019, at 19:19, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
>>>
>>> Then allowed_hugepage_adjust() would look something like:
>>>
>>> static void allowed_hugepage_adjust(struct kvm_vcpu *vcpu, gfn_t gfn,
>>> kvm_pfn_t *pfnp, int *levelp, int max_level)
>>> {
>>> kvm_pfn_t pfn = *pfnp;
>>> int level = *levelp;
>>> unsigned long mask;
>>>
>>> if (is_error_noslot_pfn(pfn) || !kvm_is_reserved_pfn(pfn) ||
>>> level == PT_PAGE_TABLE_LEVEL)
>>> return;
>>>
>>> /*
>>> * mmu_notifier_retry() was successful and mmu_lock is held, so
>>> * the pmd/pud can't be split from under us.
>>> */
>>> level = host_pfn_mapping_level(vcpu->kvm, gfn, pfn);
>>>
>>> *levelp = level = min(level, max_level);
>>> mask = KVM_PAGES_PER_HPAGE(level) - 1;
>>> VM_BUG_ON((gfn & mask) != (pfn & mask));
>>> *pfnp = pfn & ~mask;
>>
>> Why don’t you still need to kvm_release_pfn_clean() for original pfn and
>> kvm_get_pfn() for new huge-page start pfn?
>
> That code is gone in kvm/queue. thp_adjust() is now called from
> __direct_map() and FNAME(fetch), and so its pfn adjustment doesn't bleed
> back to the page fault handlers. The only reason the put/get pfn code
> existed was because the page fault handlers called kvm_release_pfn_clean()
> on the pfn, i.e. they would have put the wrong pfn.
Ack. Thanks for the explaining this.
next prev parent reply other threads:[~2019-12-13 20:40 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 18:22 [PATCH v5 0/2] kvm: Use huge pages for DAX-backed files Barret Rhoden
2019-12-12 18:22 ` [PATCH v5 1/2] mm: make dev_pagemap_mapping_shift() externally visible Barret Rhoden
2019-12-13 17:47 ` Sean Christopherson
2019-12-13 18:13 ` Dan Williams
2019-12-16 17:59 ` Barret Rhoden
2019-12-18 0:18 ` Sean Christopherson
2020-01-15 18:33 ` Paolo Bonzini
2019-12-12 18:22 ` [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files Barret Rhoden
2019-12-12 18:47 ` Liran Alon
2019-12-12 18:49 ` Liran Alon
2019-12-12 19:55 ` Barret Rhoden
2019-12-13 1:07 ` Liran Alon
2019-12-13 14:13 ` Barret Rhoden
2019-12-13 17:19 ` Sean Christopherson
2019-12-13 17:31 ` Liran Alon
2019-12-13 17:50 ` Sean Christopherson
2019-12-13 18:08 ` Liran Alon [this message]
2019-12-16 16:05 ` Barret Rhoden
2020-01-07 19:05 ` Sean Christopherson
2020-01-07 19:19 ` Barret Rhoden
2020-01-08 1:20 ` Sean Christopherson
2020-01-08 1:39 ` Dan Williams
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