Linux Virtualization - Feb 2023 - [PATCH v2] x86/paravirt: merge activate_mm and dup_mmap callbacks

On 2/6/23 11:59 PM, Juergen Gross wrote:
> 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.
> 
> Signed-off-by: Juergen Gross <jgross at suse.com>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky at oracle.com>

Reviewed-by: Srivatsa S. Bhat (VMware) <srivatsa at csail.mit.edu>

Regards,
Srivatsa
VMware Photon OS
> ---
> V2:
> - expand commit message (Srivatsa S. Bhat)
> ---
>  arch/x86/include/asm/mmu_context.h    |  4 ++--
>  arch/x86/include/asm/paravirt.h       | 14 +++-----------
>  arch/x86/include/asm/paravirt_types.h |  7 ++-----
>  arch/x86/kernel/paravirt.c            |  3 +--
>  arch/x86/mm/init.c                    |  2 +-
>  arch/x86/xen/mmu_pv.c                 | 12 ++----------
>  6 files changed, 11 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/x86/include/asm/mmu_context.h
b/arch/x86/include/asm/mmu_context.h
> index b8d40ddeab00..6a14b6c2165c 100644
> --- a/arch/x86/include/asm/mmu_context.h
> +++ b/arch/x86/include/asm/mmu_context.h
> @@ -134,7 +134,7 @@ 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);
>  
> @@ -167,7 +167,7 @@ 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);
>  }
>  
> diff --git a/arch/x86/include/asm/paravirt.h
b/arch/x86/include/asm/paravirt.h
> index 73e9522db7c1..07bbdceaf35a 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -332,16 +332,9 @@ 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)
> @@ -787,8 +780,7 @@ 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
> diff --git a/arch/x86/include/asm/paravirt_types.h
b/arch/x86/include/asm/paravirt_types.h
> index 8c1da419260f..71bf64b963df 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/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);
> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
> index 327757afb027..ff1109b9c6cd 100644
> --- a/arch/x86/kernel/paravirt.c
> +++ b/arch/x86/kernel/paravirt.c
> @@ -352,8 +352,7 @@ 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,
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index cb258f58fdc8..cbc53da4c1b4 100644
> --- a/arch/x86/mm/init.c
> +++ b/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
> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index ee29fb558f2e..b3b8d289b9ab 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/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 = {
>

On 07.02.23 22:09, Srivatsa S. Bhat wrote:
> On 2/6/23 11:59 PM, Juergen Gross wrote:
>> 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.
>>
>> Signed-off-by: Juergen Gross <jgross at suse.com>
>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky at oracle.com>
> 
> 
> Reviewed-by: Srivatsa S. Bhat (VMware) <srivatsa at csail.mit.edu>
x86 maintainers, I think this patch should be carried via the tip tree.


Juergen

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