x86/paravirt/xen: Optimize pte_flags by marking it asparavirt_ident_[32|64] type.

[Konrad Rzeszutek Wilk]

Which means that we have to use:
 __PV_IS_CALLEE_SAVE(_paravirt_ident_64)
which requires that the pte_flags on the 'pv_mmu_ops' structure
be defined as struct paravirt_callee_save. We end up using the
_paravirt_ident_64 function for both baremetal and for Xen guests
that have PAT disabled. For those that have pat_enabled, we end
up calling xen_pte_flags.

The big benefit of making the .pte_flags as struct paravirt_callee_save
and making it PTE_IDENT is that while the code looks as so when compiled:

  ff 14 25 e8 52 c1 81 	callq  *0xffffffff81c152e8

That however, on baremetal and under Xen when !pat_enable ends up
being patched over (by using the DEF_NATIVE macro) to be:

   48 89 f8             	mov    %rdi,%rax
   66 66 66 90          	data32 data32 xchg %ax,%ax

(the 32-bit version is of course different).
For details refer to 'paravirt_patch_ident_64' function.

The Xen version which requires pat_enable==1, ends up patched
to be:

	call xen_pte_flags;

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/include/asm/paravirt.h       |   11 ++++++++++-
 arch/x86/include/asm/paravirt_types.h |    2 +-
 arch/x86/kernel/paravirt.c            |    2 +-
 arch/x86/xen/mmu.c                    |   11 +++++++++--
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 6533409..b113feb 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -464,7 +464,16 @@ static inline void pmd_update_defer(struct mm_struct *mm, unsigned long addr,
 
 static inline pteval_t pte_flags(pte_t pte)
 {
-	return pv_mmu_ops.pte_flags(pte) & PTE_FLAGS_MASK;
+	pteval_t ret;
+
+	if (sizeof(pteval_t) > sizeof(long))
+		ret =  PVOP_CALLEE2(pteval_t, pv_mmu_ops.pte_flags,
+				    pte.pte, (u64)pte.pte >> 32);
+	else
+		ret =  PVOP_CALLEE1(pteval_t, pv_mmu_ops.pte_flags,
+				    pte.pte);
+
+	return ret & PTE_FLAGS_MASK;
 }
 
 static inline pte_t __pte(pteval_t val)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 86bce9d..5890cd7c 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -288,7 +288,7 @@ struct pv_mmu_ops {
 	void (*ptep_modify_prot_commit)(struct mm_struct *mm, unsigned long addr,
 					pte_t *ptep, pte_t pte);
 
-	pteval_t (*pte_flags)(pte_t pte);
+	struct paravirt_callee_save pte_flags;
 	struct paravirt_callee_save pte_val;
 	struct paravirt_callee_save make_pte;
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 4780367..ba22188 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -462,7 +462,7 @@ struct pv_mmu_ops pv_mmu_ops = {
 #endif
 #endif /* PAGETABLE_LEVELS >= 3 */
 
-	.pte_flags = native_pte_flags,
+	.pte_flags = PTE_IDENT,
 	.pte_val = PTE_IDENT,
 	.pgd_val = PTE_IDENT,
 
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 5b79048..24e275a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1965,6 +1965,13 @@ void __init xen_ident_map_ISA(void)
 	xen_flush_tlb();
 }
 
+#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
+/* 32-bit pagetable entries */
+#define PTE_IDENT	__PV_IS_CALLEE_SAVE(_paravirt_ident_32)
+#else
+/* 64-bit pagetable entries */
+#define PTE_IDENT	__PV_IS_CALLEE_SAVE(_paravirt_ident_64)
+#endif
 static void __init xen_post_allocator_init(void)
 {
 	pv_mmu_ops.set_pte = xen_set_pte;
@@ -1986,7 +1993,7 @@ static void __init xen_post_allocator_init(void)
 #endif
 
 	if (!pat_enabled)
-		pv_mmu_ops.pte_flags = native_pte_flags;
+		pv_mmu_ops.pte_flags = PTE_IDENT;
 #ifdef CONFIG_X86_64
 	SetPagePinned(virt_to_page(level3_user_vsyscall));
 #endif
@@ -2035,7 +2042,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
 	.ptep_modify_prot_start = __ptep_modify_prot_start,
 	.ptep_modify_prot_commit = __ptep_modify_prot_commit,
 
-	.pte_flags = xen_pte_flags,
+	.pte_flags = __PV_IS_CALLEE_SAVE(xen_pte_flags),
 	.pte_val = PV_CALLEE_SAVE(xen_pte_val),
 	.pgd_val = PV_CALLEE_SAVE(xen_pgd_val),
 
-- 
1.7.7.3


--YiEDa0DAkWCtVeE4--
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