linux-kernel - [RFC 08/16] KVM: x86: Use GUP for page walk instead of __get

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Date:   Fri, 22 May 2020 15:52:06 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [RFC 08/16] KVM: x86: Use GUP for page walk instead of __get_user()

The user mapping doesn't have the page mapping for protected memory.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/kvm/mmu/paging_tmpl.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 9bdf9b7d9a96..ef0c5bc8ad7e 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -400,8 +400,14 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 			goto error;
 
 		ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
-		if (unlikely(__get_user(pte, ptep_user)))
-			goto error;
+		if (vcpu->kvm->mem_protected) {
+			if (copy_from_guest(&pte, host_addr + offset,
+					    sizeof(pte)))
+				goto error;
+		} else {
+			if (unlikely(__get_user(pte, ptep_user)))
+				goto error;
+		}
 		walker->ptep_user[walker->level - 1] = ptep_user;
 
 		trace_kvm_mmu_paging_element(pte, walker->level);
-- 
2.26.2