[xen master] x86/pagewalk: Remove opt_allow_superpage check from guest_can_use_l2_superpages()
Author: Andrew Cooper <[hidden email]>
AuthorDate: Mon Jul 24 17:28:25 2017 +0100
Commit: Andrew Cooper <[hidden email]>
CommitDate: Tue Jul 25 18:48:37 2017 +0100
x86/pagewalk: Remove opt_allow_superpage check from guest_can_use_l2_superpages()
The purpose of guest_walk_tables() is to match the behaviour of real hardware.
A PV guest can have 2M superpages in its pagetables, via the M2P (and for dom0
via the initial P2M), even if the guest isn't permitted to create arbitrary 2M
guest_can_use_l2_superpages() checking opt_allow_superpage is a piece of PV
guest policy enforcement, rather than its intended purpose of meaning "would
hardware tolerate finding an L2 superpage with these control settings?"
Signed-off-by: Andrew Cooper <[hidden email]>
Reviewed-by: Tim Deegan <[hidden email]>
Reviewed-by: Wei Liu <[hidden email]>
xen/include/asm-x86/guest_pt.h | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/xen/include/asm-x86/guest_pt.h b/xen/include/asm-x86/guest_pt.h
index 72126d5..08031c8 100644
@@ -205,15 +205,17 @@ static inline guest_l4e_t guest_l4e_from_gfn(gfn_t gfn, u32 flags)
static inline bool guest_can_use_l2_superpages(const struct vcpu *v)
+ * PV guests use Xen's paging settings. Being 4-level, 2M
+ * superpages are unconditionally supported.
* The L2 _PAGE_PSE bit must be honoured in HVM guests, whenever
* CR4.PSE is set or the guest is in PAE or long mode.
* It's also used in the dummy PT for vcpus with CR0.PG cleared.
- return (is_pv_vcpu(v)
- ? opt_allow_superpage
- : (GUEST_PAGING_LEVELS != 2
- || !hvm_paging_enabled(v)
- || (v->arch.hvm_vcpu.guest_cr & X86_CR4_PSE)));
+ return (is_pv_vcpu(v) ||
+ GUEST_PAGING_LEVELS != 2 ||
+ !hvm_paging_enabled(v) ||
+ (v->arch.hvm_vcpu.guest_cr & X86_CR4_PSE));
static inline bool guest_can_use_l3_superpages(const struct domain *d)
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