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    Subject[PATCH 4.19 187/195] KVM: Play nice with read-only memslots when querying host page size
    Date
    From: Sean Christopherson <sean.j.christopherson@intel.com>

    [ Upstream commit 42cde48b2d39772dba47e680781a32a6c4b7dc33 ]

    Avoid the "writable" check in __gfn_to_hva_many(), which will always fail
    on read-only memslots due to gfn_to_hva() assuming writes. Functionally,
    this allows x86 to create large mappings for read-only memslots that
    are backed by HugeTLB mappings.

    Note, the changelog for commit 05da45583de9 ("KVM: MMU: large page
    support") states "If the largepage contains write-protected pages, a
    large pte is not used.", but "write-protected" refers to pages that are
    temporarily read-only, e.g. read-only memslots didn't even exist at the
    time.

    Fixes: 4d8b81abc47b ("KVM: introduce readonly memslot")
    Cc: stable@vger.kernel.org
    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    [Redone using kvm_vcpu_gfn_to_memslot_prot. - Paolo]
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    virt/kvm/kvm_main.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index df7ece0bfcbd3..beec19fcf8cdb 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -1301,7 +1301,7 @@ unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn)

    size = PAGE_SIZE;

    - addr = kvm_vcpu_gfn_to_hva(vcpu, gfn);
    + addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gfn, NULL);
    if (kvm_is_error_hva(addr))
    return PAGE_SIZE;

    --
    2.20.1


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