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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 07/10] xen/arm: Add handling write fault for dirty-page tracing
On Thu, 1 Aug 2013, Jaeyong Yoo wrote:
> Add handling write fault in do_trap_data_abort_guest for dirty-page tracing.
> Rather than maintaining a bitmap for dirty pages, we use the avail bit in p2m
> entry.
> For locating the write fault pte in guest p2m, we use virtual-linear page
> table
> that slots guest p2m into xen's virtual memory.
>
> Signed-off-by: Jaeyong Yoo <jaeyong.yoo@xxxxxxxxxxx>
Looks good to me.
I would appreciated some more comments in the code to explain the
inner working of the vlp2m.
Nonetheless:
Reviewed-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> xen/arch/arm/mm.c | 110
> +++++++++++++++++++++++++++++++++++++++-
> xen/arch/arm/traps.c | 16 +++++-
> xen/include/asm-arm/domain.h | 11 ++++
> xen/include/asm-arm/mm.h | 5 ++
> xen/include/asm-arm/processor.h | 2 +
> 5 files changed, 142 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 9d5d3e0..a24afe6 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -680,7 +680,6 @@ void destroy_xen_mappings(unsigned long v, unsigned long
> e)
> create_xen_entries(REMOVE, v, 0, (e - v) >> PAGE_SHIFT, 0);
> }
>
> -enum mg { mg_clear, mg_ro, mg_rw, mg_rx };
> static void set_pte_flags_on_range(const char *p, unsigned long l, enum mg
> mg)
> {
> lpae_t pte;
> @@ -1214,6 +1213,115 @@ int is_iomem_page(unsigned long mfn)
> return 1;
> return 0;
> }
> +
> +static uint64_t find_guest_p2m_mfn(struct domain *d, paddr_t addr)
> +{
> + lpae_t *first = NULL, *second = NULL;
> + struct p2m_domain *p2m = &d->arch.p2m;
> + uint64_t mfn = -EFAULT;
> +
> + if ( first_table_offset(addr) >= LPAE_ENTRIES )
> + return mfn;
> +
> + first = __map_domain_page(p2m->first_level);
> +
> + if ( !first ||
> + !first[first_table_offset(addr)].walk.valid ||
> + !first[first_table_offset(addr)].walk.table )
> + goto done;
> +
> + second = map_domain_page(first[first_table_offset(addr)].walk.base);
> +
> + if ( !second ||
> + !second[second_table_offset(addr)].walk.valid ||
> + !second[second_table_offset(addr)].walk.table )
> + goto done;
> +
> + mfn = second[second_table_offset(addr)].walk.base;
> +
> +done:
> + if ( second ) unmap_domain_page(second);
> + if ( first ) unmap_domain_page(first);
> +
> + return mfn;
> +}
> +
> +/*
> + * routine for dirty-page tracing
> + *
> + * On first write, it page faults, its entry is changed to read-write,
> + * and on retry the write succeeds.
> + *
> + * for locating p2m of the faulting entry, we use virtual-linear page table.
> + */
> +int handle_page_fault(struct domain *d, paddr_t addr)
> +{
> + int rc = 0;
> + struct p2m_domain *p2m = &d->arch.p2m;
> + uint64_t gma_start;
> + int gma_third_index;
> + int xen_second_linear, xen_third_table;
> + lpae_t *xen_third;
> + lpae_t *vlp2m_pte;
> +
> + BUG_ON( !d->arch.map_domain.nr_banks );
> +
> + gma_start = d->arch.map_domain.bank[0].start;
> + gma_third_index = third_linear_offset(addr - gma_start);
> + vlp2m_pte = (lpae_t *)(d->arch.dirty.vlpt_start +
> + sizeof(lpae_t) * gma_third_index);
> +
> + BUG_ON( (void *)vlp2m_pte > d->arch.dirty.vlpt_end );
> +
> + spin_lock(&p2m->lock);
> +
> + xen_second_linear = second_linear_offset((unsigned long)vlp2m_pte);
> + xen_third_table = third_table_offset((unsigned long)vlp2m_pte);
> +
> + /* starting from xen second level page table */
> + if ( !xen_second[xen_second_linear].pt.valid )
> + {
> + unsigned long va = (unsigned long)vlp2m_pte & ~(PAGE_SIZE-1);
> +
> + rc = create_xen_table(&xen_second[second_linear_offset(va)]);
> + if ( rc < 0 )
> + goto out;
> + }
> +
> + BUG_ON( !xen_second[xen_second_linear].pt.valid );
> +
> + /* at this point, xen second level pt has valid entry
> + * check again the validity of third level pt */
> + xen_third = __va(pfn_to_paddr(xen_second[xen_second_linear].pt.base));
> +
> + /* xen third-level page table invalid */
> + if ( !xen_third[xen_third_table].p2m.valid )
> + {
> + uint64_t mfn = find_guest_p2m_mfn(d, addr);
> + lpae_t pte = mfn_to_xen_entry(mfn);
> + unsigned long va = (unsigned long)vlp2m_pte & ~(PAGE_SIZE-1);
> +
> + pte.pt.table = 1; /* 4k mappings always have this bit set */
> + write_pte(&xen_third[xen_third_table], pte);
> + flush_xen_data_tlb_range_va(va, PAGE_SIZE);
> + }
> +
> + /* at this point, xen third level pt has valid entry: means we can access
> + * vlp2m_pte vlp2m_pte is like a fourth level pt for xen, but for guest,
> + * it is third level pt */
> + if ( vlp2m_pte->p2m.valid && vlp2m_pte->p2m.write == 0 )
> + {
> + vlp2m_pte->p2m.write = 1;
> + vlp2m_pte->p2m.avail = 1;
> + write_pte(vlp2m_pte, *vlp2m_pte);
> + flush_tlb_local();
> + }
> +
> +out:
> + spin_unlock(&p2m->lock);
> + return rc;
> +}
> +
> /*
> * Local variables:
> * mode: C
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 1b9209d..f844f56 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -1226,7 +1226,12 @@ static void do_trap_data_abort_guest(struct
> cpu_user_regs *regs,
> goto bad_data_abort;
>
> /* XXX: Decode the instruction if ISS is not valid */
> - if ( !dabt.valid )
> + /* Note: add additional check before goto bad_data_abort. dabt.valid
> + * bit is for telling the validity of ISS[23:16] bits. For dirty-page
> + * tracing, we need to see DFSC bits. If DFSC bits are indicating the
> + * possibility of dirty page tracing, do not go to bad_data_abort */
> + if ( !dabt.valid &&
> + (dabt.dfsc & FSC_MASK) != (FSC_FLT_PERM + FSC_3D_LEVEL) &&
> dabt.write)
> goto bad_data_abort;
>
> if (handle_mmio(&info))
> @@ -1235,6 +1240,15 @@ static void do_trap_data_abort_guest(struct
> cpu_user_regs *regs,
> return;
> }
>
> + /* handle permission fault on write */
> + if ( (dabt.dfsc & FSC_MASK) == (FSC_FLT_PERM + FSC_3D_LEVEL) &&
> dabt.write )
> + {
> + if ( current->domain->arch.dirty.mode == 0 )
> + goto bad_data_abort;
> + if ( handle_page_fault(current->domain, info.gpa) == 0 )
> + return;
> + }
> +
> bad_data_abort:
>
> msg = decode_fsc( dabt.dfsc, &level);
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 0c80c65..413b89a 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -110,6 +110,17 @@ struct arch_domain
> spinlock_t lock;
> } uart0;
>
> + /* dirty-page tracing */
> + struct {
> + spinlock_t lock;
> + int mode;
> + unsigned int count;
> + uint32_t gmfn_guest_start; /* guest physical memory start address */
> + void *vlpt_start; /* va-start of guest p2m */
> + void *vlpt_end; /* va-end of guest p2m */
> + struct page_info *head; /* maintain the mapped vaddrs */
> + } dirty;
> +
> struct dt_mem_info map_domain;
> spinlock_t map_lock;
> } __cacheline_aligned;
> diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
> index 404ec4d..fd976e3 100644
> --- a/xen/include/asm-arm/mm.h
> +++ b/xen/include/asm-arm/mm.h
> @@ -328,6 +328,11 @@ static inline void put_page_and_type(struct page_info
> *page)
> put_page(page);
> }
>
> +enum mg { mg_clear, mg_ro, mg_rw, mg_rx };
> +
> +/* routine for dirty-page tracing */
> +int handle_page_fault(struct domain *d, paddr_t addr);
> +
> #endif /* __ARCH_ARM_MM__ */
> /*
> * Local variables:
> diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
> index 06b0b25..34c21de 100644
> --- a/xen/include/asm-arm/processor.h
> +++ b/xen/include/asm-arm/processor.h
> @@ -383,6 +383,8 @@ union hsr {
> #define FSC_CPR (0x3a) /* Coprocossor Abort */
>
> #define FSC_LL_MASK (0x03<<0)
> +#define FSC_MASK (0x3f) /* Fault status mask */
> +#define FSC_3D_LEVEL (0x03) /* Third level fault*/
>
> /* Time counter hypervisor control register */
> #define CNTHCTL_PA (1u<<0) /* Kernel/user access to physical counter */
> --
> 1.8.1.2
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
>
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