From: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
Fix regression introduced by
commit e30d2a170506830d5eef5e9d7990c5aedf1b0a51
KVM: MMU: Optimize guest page table walk
On x86_32, get_user() does not support 64-bit values and we fail to
build KVM at the point of 64-bit paging.
This patch fixes this by using get_user() twice for that condition.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
Reported-by: Jan Kiszka <jan.kiszka@xxxxxx>
---
arch/x86/kvm/paging_tmpl.h | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 652d56c..7d36ac9 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -115,6 +115,20 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
return access;
}
+static int FNAME(read_gpte)(pt_element_t *pte, pt_element_t __user *ptep_user)
+{
+#if defined(CONFIG_X86_32) && (PTTYPE == 64)
+ u32 *p = (u32 *)pte;
+ u32 __user *p_user = (u32 __user *)ptep_user;
+
+ if (unlikely(get_user(*p, p_user)))
+ return -EFAULT;
+ return get_user(*(p + 1), p_user + 1);
+#else
+ return get_user(*pte, ptep_user);
+#endif
+}
+
/*
* Fetch a guest pte for a guest virtual address
*/
@@ -185,7 +199,7 @@ walk:
}
ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
- if (unlikely(get_user(pte, ptep_user))) {
+ if (unlikely(FNAME(read_gpte)(&pte, ptep_user))) {
present = false;
break;
}
--
1.7.1
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