Nicholas Piggin <npig...@gmail.com> writes:
> The page fault handling still has some complex logic particularly around
> hash table handling, in asm. Implement this in C instead.
>
Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> ---
> arch/powerpc/include/asm/book3s/64/mmu-hash.h | 1 +
> arch/powerpc/include/asm/bug.h | 1 +
> arch/powerpc/kernel/exceptions-64s.S | 131 +++---------------
> arch/powerpc/mm/book3s64/hash_utils.c | 77 ++++++----
> arch/powerpc/mm/fault.c | 57 +++++++-
> 5 files changed, 127 insertions(+), 140 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> index 683a9c7d1b03..bc8c91f2d26f 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> @@ -453,6 +453,7 @@ static inline unsigned long hpt_hash(unsigned long vpn,
> #define HPTE_LOCAL_UPDATE 0x1
> #define HPTE_NOHPTE_UPDATE 0x2
>
> +int do_hash_fault(struct pt_regs *regs, unsigned long ea, unsigned long
> dsisr);
> extern int __hash_page_4K(unsigned long ea, unsigned long access,
> unsigned long vsid, pte_t *ptep, unsigned long trap,
> unsigned long flags, int ssize, int subpage_prot);
> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> index 338f36cd9934..c0e9b7a967a8 100644
> --- a/arch/powerpc/include/asm/bug.h
> +++ b/arch/powerpc/include/asm/bug.h
> @@ -112,6 +112,7 @@
>
> struct pt_regs;
> extern int do_page_fault(struct pt_regs *, unsigned long, unsigned long);
> +int hash__do_page_fault(struct pt_regs *, unsigned long, unsigned long);
> extern void bad_page_fault(struct pt_regs *, unsigned long, int);
> extern void _exception(int, struct pt_regs *, int, unsigned long);
> extern void _exception_pkey(struct pt_regs *, unsigned long, int);
> diff --git a/arch/powerpc/kernel/exceptions-64s.S
> b/arch/powerpc/kernel/exceptions-64s.S
> index 4d01f09ecf80..336fa1fa39d1 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -1401,14 +1401,15 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
> *
> * Handling:
> * - Hash MMU
> - * Go to do_hash_page first to see if the HPT can be filled from an entry
> in
> - * the Linux page table. Hash faults can hit in kernel mode in a fairly
> + * Go to do_hash_fault, which attempts to fill the HPT from an entry in the
> + * Linux page table. Hash faults can hit in kernel mode in a fairly
> * arbitrary state (e.g., interrupts disabled, locks held) when accessing
> * "non-bolted" regions, e.g., vmalloc space. However these should always
> be
> - * backed by Linux page tables.
> + * backed by Linux page table entries.
> *
> - * If none is found, do a Linux page fault. Linux page faults can happen in
> - * kernel mode due to user copy operations of course.
> + * If no entry is found the Linux page fault handler is invoked (by
> + * do_hash_fault). Linux page faults can happen in kernel mode due to user
> + * copy operations of course.
> *
> * KVM: The KVM HDSI handler may perform a load with MSR[DR]=1 in guest
> * MMU context, which may cause a DSI in the host, which must go to the
> @@ -1439,13 +1440,17 @@ EXC_COMMON_BEGIN(data_access_common)
> GEN_COMMON data_access
> ld r4,_DAR(r1)
> ld r5,_DSISR(r1)
> + addi r3,r1,STACK_FRAME_OVERHEAD
> BEGIN_MMU_FTR_SECTION
> - ld r6,_MSR(r1)
> - li r3,0x300
> - b do_hash_page /* Try to handle as hpte fault */
> + bl do_hash_fault
> MMU_FTR_SECTION_ELSE
> - b handle_page_fault
> + bl do_page_fault
> ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
> + cmpdi r3,0
> + beq+ interrupt_return
> + /* We need to restore NVGPRS */
> + REST_NVGPRS(r1)
> + b interrupt_return
>
> GEN_KVM data_access
>
> @@ -1540,13 +1545,17 @@ EXC_COMMON_BEGIN(instruction_access_common)
> GEN_COMMON instruction_access
> ld r4,_DAR(r1)
> ld r5,_DSISR(r1)
> + addi r3,r1,STACK_FRAME_OVERHEAD
> BEGIN_MMU_FTR_SECTION
> - ld r6,_MSR(r1)
> - li r3,0x400
> - b do_hash_page /* Try to handle as hpte fault */
> + bl do_hash_fault
> MMU_FTR_SECTION_ELSE
> - b handle_page_fault
> + bl do_page_fault
> ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
> + cmpdi r3,0
> + beq+ interrupt_return
> + /* We need to restore NVGPRS */
> + REST_NVGPRS(r1)
> + b interrupt_return
>
> GEN_KVM instruction_access
>
> @@ -3202,99 +3211,3 @@ disable_machine_check:
> RFI_TO_KERNEL
> 1: mtlr r0
> blr
> -
> -/*
> - * Hash table stuff
> - */
> - .balign IFETCH_ALIGN_BYTES
> -do_hash_page:
> -#ifdef CONFIG_PPC_BOOK3S_64
> - lis r0,(DSISR_BAD_FAULT_64S | DSISR_DABRMATCH | DSISR_KEYFAULT)@h
> - ori r0,r0,DSISR_BAD_FAULT_64S@l
> - and. r0,r5,r0 /* weird error? */
> - bne- handle_page_fault /* if not, try to insert a HPTE */
> -
> - /*
> - * If we are in an "NMI" (e.g., an interrupt when soft-disabled), then
> - * don't call hash_page, just fail the fault. This is required to
> - * prevent re-entrancy problems in the hash code, namely perf
> - * interrupts hitting while something holds H_PAGE_BUSY, and taking a
> - * hash fault. See the comment in hash_preload().
> - */
> - ld r11, PACA_THREAD_INFO(r13)
> - lwz r0,TI_PREEMPT(r11)
> - andis. r0,r0,NMI_MASK@h
> - bne 77f
> -
> - /*
> - * r3 contains the trap number
> - * r4 contains the faulting address
> - * r5 contains dsisr
> - * r6 msr
> - *
> - * at return r3 = 0 for success, 1 for page fault, negative for error
> - */
> - bl __hash_page /* build HPTE if possible */
> - cmpdi r3,0 /* see if __hash_page succeeded
> */
> -
> - /* Success */
> - beq interrupt_return /* Return from exception on success */
> -
> - /* Error */
> - blt- 13f
> -
> - /* Reload DAR/DSISR into r4/r5 for the DABR check below */
> - ld r4,_DAR(r1)
> - ld r5,_DSISR(r1)
> -#endif /* CONFIG_PPC_BOOK3S_64 */
> -
> -/* Here we have a page fault that hash_page can't handle. */
> -handle_page_fault:
> -11: andis. r0,r5,DSISR_DABRMATCH@h
> - bne- handle_dabr_fault
> - addi r3,r1,STACK_FRAME_OVERHEAD
> - bl do_page_fault
> - cmpdi r3,0
> - beq+ interrupt_return
> - mr r5,r3
> - addi r3,r1,STACK_FRAME_OVERHEAD
> - ld r4,_DAR(r1)
> - bl bad_page_fault
> - b interrupt_return
> -
> -/* We have a data breakpoint exception - handle it */
> -handle_dabr_fault:
> - ld r4,_DAR(r1)
> - ld r5,_DSISR(r1)
> - addi r3,r1,STACK_FRAME_OVERHEAD
> - bl do_break
> - /*
> - * do_break() may have changed the NV GPRS while handling a breakpoint.
> - * If so, we need to restore them with their updated values.
> - */
> - REST_NVGPRS(r1)
> - b interrupt_return
> -
> -
> -#ifdef CONFIG_PPC_BOOK3S_64
> -/* We have a page fault that hash_page could handle but HV refused
> - * the PTE insertion
> - */
> -13: mr r5,r3
> - addi r3,r1,STACK_FRAME_OVERHEAD
> - ld r4,_DAR(r1)
> - bl low_hash_fault
> - b interrupt_return
> -#endif
> -
> -/*
> - * We come here as a result of a DSI at a point where we don't want
> - * to call hash_page, such as when we are accessing memory (possibly
> - * user memory) inside a PMU interrupt that occurred while interrupts
> - * were soft-disabled. We want to invoke the exception handler for
> - * the access, or panic if there isn't a handler.
> - */
> -77: addi r3,r1,STACK_FRAME_OVERHEAD
> - li r5,SIGSEGV
> - bl bad_page_fault
> - b interrupt_return
> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
> b/arch/powerpc/mm/book3s64/hash_utils.c
> index 24702c0a92e0..bfa1b1966218 100644
> --- a/arch/powerpc/mm/book3s64/hash_utils.c
> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
> @@ -1510,16 +1510,40 @@ int hash_page(unsigned long ea, unsigned long access,
> unsigned long trap,
> }
> EXPORT_SYMBOL_GPL(hash_page);
>
> -int __hash_page(unsigned long trap, unsigned long ea, unsigned long dsisr,
> - unsigned long msr)
> +int do_hash_fault(struct pt_regs *regs, unsigned long ea, unsigned long
> dsisr)
> {
> unsigned long access = _PAGE_PRESENT | _PAGE_READ;
> unsigned long flags = 0;
> - struct mm_struct *mm = current->mm;
> - unsigned int region_id = get_region_id(ea);
> + struct mm_struct *mm;
> + unsigned int region_id;
> + int err;
> +
> + if (unlikely(dsisr & (DSISR_BAD_FAULT_64S | DSISR_DABRMATCH |
> DSISR_KEYFAULT)))
> + goto _do_page_fault;
> +
> + /*
> + * If we are in an "NMI" (e.g., an interrupt when soft-disabled), then
> + * don't call hash_page, just fail the fault. This is required to
> + * prevent re-entrancy problems in the hash code, namely perf
> + * interrupts hitting while something holds H_PAGE_BUSY, and taking a
> + * hash fault. See the comment in hash_preload().
> + *
> + * We come here as a result of a DSI at a point where we don't want
> + * to call hash_page, such as when we are accessing memory (possibly
> + * user memory) inside a PMU interrupt that occurred while interrupts
> + * were soft-disabled. We want to invoke the exception handler for
> + * the access, or panic if there isn't a handler.
> + */
> + if (unlikely(in_nmi())) {
> + bad_page_fault(regs, ea, SIGSEGV);
> + return 0;
> + }
>
> + region_id = get_region_id(ea);
> if ((region_id == VMALLOC_REGION_ID) || (region_id == IO_REGION_ID))
> mm = &init_mm;
> + else
> + mm = current->mm;
>
> if (dsisr & DSISR_NOHPTE)
> flags |= HPTE_NOHPTE_UPDATE;
> @@ -1535,13 +1559,31 @@ int __hash_page(unsigned long trap, unsigned long ea,
> unsigned long dsisr,
> * 2) user space access kernel space.
> */
> access |= _PAGE_PRIVILEGED;
> - if ((msr & MSR_PR) || (region_id == USER_REGION_ID))
> + if (user_mode(regs) || (region_id == USER_REGION_ID))
> access &= ~_PAGE_PRIVILEGED;
>
> - if (trap == 0x400)
> + if (regs->trap == 0x400)
> access |= _PAGE_EXEC;
>
> - return hash_page_mm(mm, ea, access, trap, flags);
> + err = hash_page_mm(mm, ea, access, regs->trap, flags);
> + if (unlikely(err < 0)) {
> + // failed to instert a hash PTE due to an hypervisor error
> + if (user_mode(regs)) {
> + if (IS_ENABLED(CONFIG_PPC_SUBPAGE_PROT) && err == -2)
> + _exception(SIGSEGV, regs, SEGV_ACCERR, ea);
> + else
> + _exception(SIGBUS, regs, BUS_ADRERR, ea);
> + } else {
> + bad_page_fault(regs, ea, SIGBUS);
> + }
> + err = 0;
> +
> + } else if (err) {
> +_do_page_fault:
> + err = hash__do_page_fault(regs, ea, dsisr);
> + }
> +
> + return err;
> }
>
> #ifdef CONFIG_PPC_MM_SLICES
> @@ -1841,27 +1883,6 @@ void flush_hash_range(unsigned long number, int local)
> }
> }
>
> -/*
> - * low_hash_fault is called when we the low level hash code failed
> - * to instert a PTE due to an hypervisor error
> - */
> -void low_hash_fault(struct pt_regs *regs, unsigned long address, int rc)
> -{
> - enum ctx_state prev_state = exception_enter();
> -
> - if (user_mode(regs)) {
> -#ifdef CONFIG_PPC_SUBPAGE_PROT
> - if (rc == -2)
> - _exception(SIGSEGV, regs, SEGV_ACCERR, address);
> - else
> -#endif
> - _exception(SIGBUS, regs, BUS_ADRERR, address);
> - } else
> - bad_page_fault(regs, address, SIGBUS);
> -
> - exception_exit(prev_state);
> -}
> -
> long hpte_insert_repeating(unsigned long hash, unsigned long vpn,
> unsigned long pa, unsigned long rflags,
> unsigned long vflags, int psize, int ssize)
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 0add963a849b..e65a49f246ef 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -370,7 +370,9 @@ static void sanity_check_fault(bool is_write, bool
> is_user,
> #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
> #if defined(CONFIG_PPC_8xx)
> #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
> -#elif defined(CONFIG_PPC64)
> +#elif defined(CONFIG_PPC_BOOK3S_64)
> +#define page_fault_is_bad(__err) ((__err) & (DSISR_BAD_FAULT_64S |
> DSISR_DABRMATCH))
> +#elif defined(CONFIG_PPC_BOOK3E_64)
> #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
> #else
> #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
> @@ -406,6 +408,9 @@ static int __do_page_fault(struct pt_regs *regs, unsigned
> long address,
> return 0;
>
> if (unlikely(page_fault_is_bad(error_code))) {
> + if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && (error_code &
> DSISR_DABRMATCH))
> + return -1;
> +
> if (is_user) {
> _exception(SIGBUS, regs, BUS_OBJERR, address);
> return 0;
> @@ -548,12 +553,58 @@ int do_page_fault(struct pt_regs *regs, unsigned long
> address,
> unsigned long error_code)
> {
> enum ctx_state prev_state = exception_enter();
> - int rc = __do_page_fault(regs, address, error_code);
> + int err;
> +
> + err = __do_page_fault(regs, address, error_code);
> +
> +#ifdef CONFIG_PPC_BOOK3S_64
> + /* 32 and 64e handle errors in their asm code */
> + if (unlikely(err)) {
> + if (err > 0) {
> + bad_page_fault(regs, address, err);
> + err = 0;
> + } else {
> + /*
> + * do_break() may change NV GPRS while handling the
> + * breakpoint. Return -ve to caller to do that.
> + */
> + do_break(regs, address, error_code);
> + }
> + }
> +#endif
> +
> exception_exit(prev_state);
> - return rc;
> +
> + return err;
> }
> NOKPROBE_SYMBOL(do_page_fault);
>
> +#ifdef CONFIG_PPC_BOOK3S_64
> +/* Same as do_page_fault but interrupt entry has already run in
> do_hash_fault */
> +int hash__do_page_fault(struct pt_regs *regs, unsigned long address,
> + unsigned long error_code)
> +{
> + int err;
> +
> + err = __do_page_fault(regs, address, error_code);
> + if (unlikely(err)) {
> + if (err > 0) {
> + bad_page_fault(regs, address, err);
> + err = 0;
> + } else {
> + /*
> + * do_break() may change NV GPRS while handling the
> + * breakpoint. Return -ve to caller to do that.
> + */
> + do_break(regs, address, error_code);
> + }
> + }
> +
> + return err;
> +}
> +NOKPROBE_SYMBOL(hash__do_page_fault);
> +#endif
> +
> /*
> * bad_page_fault is called when we have a bad access from the kernel.
> * It is called from the DSI and ISI handlers in head.S and from some
> --
> 2.23.0
