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Message-ID: <dc5fbb2e-6a23-15e5-a451-e069e90a0656@csail.mit.edu>
Date: Tue, 7 Feb 2023 13:09:15 -0800
From: "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
To: Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
x86@...nel.org, virtualization@...ts.linux-foundation.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Alexey Makhalov <amakhalov@...are.com>,
VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
xen-devel@...ts.xenproject.org
Subject: Re: [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@...e.com>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Reviewed-by: Srivatsa S. Bhat (VMware) <srivatsa@...il.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 = {
>
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