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SubjectRe: [PATCH v3 0/3] kvm: Use huge pages for DAX-backed files
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-yi.z.zhang@intel.com (Bad email address / failure)

Sorry about that.

On 4/4/19 4:23 PM, Barret Rhoden wrote:
> This patch series depends on DAX pages not being PageReserved. Once
> that is in place, these changes will let KVM use huge pages with
> DAX-backed files.
>
> From previous discussions[1], it sounds like DAX might not need to keep
> the PageReserved bit, but that it hadn't been sorted out yet.
>
> Without the PageReserved change, KVM and DAX still work with these
> patches, simply without huge pages - which is the current situation.
>
> If you want to test the huge-page functionality as if DAX pages weren't
> PageReserved for KVM, this hack does the trick:
>
> ------------------
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index c44985375e7f..ee539eec1fb8 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -153,6 +153,10 @@ __weak int kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>
> bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
> {
> + // XXX hack
> + if (is_zone_device_page(pfn_to_page(pfn)))
> + return false;
> +
> if (pfn_valid(pfn))
> return PageReserved(pfn_to_page(pfn));
>
> ------------------
>
> Perhaps if we are going to leave DAX pages marked PageReserved, then I
> can make that hack into a proper commit and have KVM alone treat DAX
> pages as if they are not reserved.
>
> v2 -> v3:
> v2: https://lore.kernel.org/lkml/20181114215155.259978-1-brho@google.com/
> - Updated Acks/Reviewed-by
> - Rebased onto linux-next
>
> v1 -> v2:
> https://lore.kernel.org/lkml/20181109203921.178363-1-brho@google.com/
> - Updated Acks/Reviewed-by
> - Minor touchups
> - Added patch to remove redundant PageReserved() check
> - Rebased onto linux-next
>
> RFC/discussion thread:
> https://lore.kernel.org/lkml/20181029210716.212159-1-brho@google.com/
>
> [1] https://lore.kernel.org/lkml/ee8cc068-903c-d87e-f418-ade46786249e@redhat.com/
>
> Barret Rhoden (3):
> mm: make dev_pagemap_mapping_shift() externally visible
> kvm: Use huge pages for DAX-backed files
> kvm: remove redundant PageReserved() check
>
> arch/x86/kvm/mmu.c | 33 +++++++++++++++++++++++++++++++--
> include/linux/mm.h | 3 +++
> mm/memory-failure.c | 38 +++-----------------------------------
> mm/util.c | 34 ++++++++++++++++++++++++++++++++++
> virt/kvm/kvm_main.c | 8 ++------
> 5 files changed, 73 insertions(+), 43 deletions(-)
>

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