x86/paravirt: Merge activate_mm() and dup_mmap() callbacks

The two paravirt callbacks .mmu.activate_mm() and .mmu.dup_mmap() are
sharing the same implementations in all cases: for Xen PV guests they
are pinning the PGD of the new mm_struct, and for all other cases they
are a NOP.

In the end, both callbacks are meant to register an address space with
the underlying hypervisor, so there needs to be only a single callback
for that purpose.

So merge them to a common callback .mmu.enter_mmap() (in contrast to the
corresponding already existing .mmu.exit_mmap()).

As the first parameter of the old callbacks isn't used, drop it from the
replacement one.

  [ bp: Remove last occurrence of paravirt_activate_mm() in
    asm/mmu_context.h ]

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
Link: https://lore.kernel.org/r/20230207075902.7539-1-jgross@suse.com

Author: jgross1

arch/x86/include/asm/mmu_context.h

@@ -16,13 +16,6 @@
 
 extern atomic64_t last_mm_ctx_id;
 
-#ifndef CONFIG_PARAVIRT_XXL
-static inline void paravirt_activate_mm(struct mm_struct *prev,
-					struct mm_struct *next)
-{
-}
-#endif	/* !CONFIG_PARAVIRT_XXL */
-
 #ifdef CONFIG_PERF_EVENTS
 DECLARE_STATIC_KEY_FALSE(rdpmc_never_available_key);
 DECLARE_STATIC_KEY_FALSE(rdpmc_always_available_key);
@@ -135,7 +128,7 @@ extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 
 #define activate_mm(prev, next)			\
 do {						\
-	paravirt_activate_mm((prev), (next));	\
+	paravirt_enter_mmap(next);		\
 	switch_mm((prev), (next), NULL);	\
 } while (0);
 
@@ -168,7 +161,7 @@ static inline void arch_dup_pkeys(struct mm_struct *oldmm,
 static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 	arch_dup_pkeys(oldmm, mm);
-	paravirt_arch_dup_mmap(oldmm, mm);
+	paravirt_enter_mmap(mm);
 	return ldt_dup_context(oldmm, mm);
 }
 

arch/x86/include/asm/paravirt.h

@@ -334,16 +334,9 @@ static inline void tss_update_io_bitmap(void)
 }
 #endif
 
-static inline void paravirt_activate_mm(struct mm_struct *prev,
-					struct mm_struct *next)
+static inline void paravirt_enter_mmap(struct mm_struct *next)
 {
-	PVOP_VCALL2(mmu.activate_mm, prev, next);
-}
-
-static inline void paravirt_arch_dup_mmap(struct mm_struct *oldmm,
-					  struct mm_struct *mm)
-{
-	PVOP_VCALL2(mmu.dup_mmap, oldmm, mm);
+	PVOP_VCALL1(mmu.enter_mmap, next);
 }
 
 static inline int paravirt_pgd_alloc(struct mm_struct *mm)
@@ -789,8 +782,7 @@ extern void default_banner(void);
 
 #ifndef __ASSEMBLY__
 #ifndef CONFIG_PARAVIRT_XXL
-static inline void paravirt_arch_dup_mmap(struct mm_struct *oldmm,
-					  struct mm_struct *mm)
+static inline void paravirt_enter_mmap(struct mm_struct *mm)
 {
 }
 #endif

arch/x86/include/asm/paravirt_types.h

@@ -164,11 +164,8 @@ struct pv_mmu_ops {
 	unsigned long (*read_cr3)(void);
 	void (*write_cr3)(unsigned long);
 
-	/* Hooks for intercepting the creation/use of an mm_struct. */
-	void (*activate_mm)(struct mm_struct *prev,
-			    struct mm_struct *next);
-	void (*dup_mmap)(struct mm_struct *oldmm,
-			 struct mm_struct *mm);
+	/* Hook for intercepting the creation/use of an mm_struct. */
+	void (*enter_mmap)(struct mm_struct *mm);
 
 	/* Hooks for allocating and freeing a pagetable top-level */
 	int  (*pgd_alloc)(struct mm_struct *mm);

arch/x86/kernel/paravirt.c

@@ -363,8 +363,7 @@ struct paravirt_patch_template pv_ops = {
 	.mmu.make_pte		= PTE_IDENT,
 	.mmu.make_pgd		= PTE_IDENT,
 
-	.mmu.dup_mmap		= paravirt_nop,
-	.mmu.activate_mm	= paravirt_nop,
+	.mmu.enter_mmap		= paravirt_nop,
 
 	.mmu.lazy_mode = {
 		.enter		= paravirt_nop,

arch/x86/mm/init.c

@@ -806,7 +806,7 @@ void __init poking_init(void)
 	BUG_ON(!poking_mm);
 
 	/* Xen PV guests need the PGD to be pinned. */
-	paravirt_arch_dup_mmap(NULL, poking_mm);
+	paravirt_enter_mmap(poking_mm);
 
 	/*
 	 * Randomize the poking address, but make sure that the following page

arch/x86/xen/mmu_pv.c

@@ -885,14 +885,7 @@ void xen_mm_unpin_all(void)
 	spin_unlock(&pgd_lock);
 }
 
-static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
-{
-	spin_lock(&next->page_table_lock);
-	xen_pgd_pin(next);
-	spin_unlock(&next->page_table_lock);
-}
-
-static void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
+static void xen_enter_mmap(struct mm_struct *mm)
 {
 	spin_lock(&mm->page_table_lock);
 	xen_pgd_pin(mm);
@@ -2153,8 +2146,7 @@ static const typeof(pv_ops) xen_mmu_ops __initconst = {
 		.make_p4d = PV_CALLEE_SAVE(xen_make_p4d),
 #endif
 
-		.activate_mm = xen_activate_mm,
-		.dup_mmap = xen_dup_mmap,
+		.enter_mmap = xen_enter_mmap,
 		.exit_mmap = xen_exit_mmap,
 
 		.lazy_mode = {