[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [RFC v2 4/6] xen/arm: Implement VLPT for guest p2m mapping in live migration
From: Jaeyong Yoo <jaeyong.yoo@xxxxxxxxxxx> Thsi patch implements VLPT (virtual-linear page table) for fast accessing of 3rd PTE of guest P2M. For more info about VLPT, please see http://www.technovelty.org/linux/virtual-linear-page-table.html. When creating a mapping for VLPT, just copy the 1st level PTE of guest p2m to xen's 2nd level PTE. Then the mapping becomes the following: xen's 1st PTE --> xen's 2nd PTE (which is the same as 1st PTE of guest p2m) --> guest p2m's 2nd PTE --> guest p2m's 3rd PTE (the memory contents where the vlpt points) This function is used in dirty-page tracing. When domU write-fault is trapped by xen, xen can immediately locate the 3rd PTE of guest p2m. The following link shows the performance comparison for handling a dirty-page between vlpt and typical page table walking. http://lists.xen.org/archives/html/xen-devel/2013-08/msg01503.html Signed-off-by: Jaeyong Yoo <jaeyong.yoo@xxxxxxxxxxx> --- xen/arch/arm/domain.c | 5 ++ xen/arch/arm/mm.c | 116 ++++++++++++++++++++++++++++++++++++++++++ xen/include/asm-arm/config.h | 7 +++ xen/include/asm-arm/domain.h | 7 +++ xen/include/asm-arm/mm.h | 17 +++++++ 5 files changed, 152 insertions(+) diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c index b125857..3f04a77 100644 --- a/xen/arch/arm/domain.c +++ b/xen/arch/arm/domain.c @@ -502,6 +502,11 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags) /* Default the virtual ID to match the physical */ d->arch.vpidr = boot_cpu_data.midr.bits; + d->arch.dirty.second_lvl_start = 0; + d->arch.dirty.second_lvl_end = 0; + d->arch.dirty.second_lvl[0] = NULL; + d->arch.dirty.second_lvl[1] = NULL; + clear_page(d->shared_info); share_xen_page_with_guest( virt_to_page(d->shared_info), d, XENSHARE_writable); diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index 473ad04..a315752 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -750,6 +750,122 @@ void *__init arch_vmap_virt_end(void) return (void *)VMAP_VIRT_END; } +/* Flush the vlpt area */ +void flush_vlpt(struct domain *d) +{ + int flush_size; + + flush_size = (d->arch.dirty.second_lvl_end - + d->arch.dirty.second_lvl_start) << SECOND_SHIFT; + + /* flushing the 3rd level mapping */ + flush_xen_data_tlb_range_va(d->arch.dirty.second_lvl_start << SECOND_SHIFT, + flush_size); +} + +/* Restore the xen page table for vlpt mapping for domain */ +void restore_vlpt(struct domain *d) +{ + int i; + + dsb(sy); + + for ( i = d->arch.dirty.second_lvl_start; i < d->arch.dirty.second_lvl_end; + ++i ) + { + int k = i % LPAE_ENTRIES; + int l = i / LPAE_ENTRIES; + + if ( xen_second[i].bits != d->arch.dirty.second_lvl[l][k].bits ) + { + write_pte(&xen_second[i], d->arch.dirty.second_lvl[l][k]); + flush_xen_data_tlb_range_va(i << SECOND_SHIFT, 1 << SECOND_SHIFT); + } + } + + dsb(sy); + isb(); +} + +/* Set up the xen page table for vlpt mapping for domain */ +int prepare_vlpt(struct domain *d) +{ + int xen_second_linear_base; + int gp2m_start_index, gp2m_end_index; + struct p2m_domain *p2m = &d->arch.p2m; + struct page_info *second_lvl_page; + paddr_t gma_start = 0; + paddr_t gma_end = 0; + lpae_t *first[2]; + int i; + uint64_t required, avail = VIRT_LIN_P2M_END - VIRT_LIN_P2M_START; + + domain_get_gpfn_range(d, &gma_start, &gma_end); + required = (gma_end - gma_start) >> LPAE_SHIFT; + + if ( required > avail ) + { + dprintk(XENLOG_ERR, "Available VLPT is small for domU guest" + "(avail: %llx, required: %llx)\n", (unsigned long long)avail, + (unsigned long long)required); + return -ENOMEM; + } + + xen_second_linear_base = second_linear_offset(VIRT_LIN_P2M_START); + + gp2m_start_index = gma_start >> FIRST_SHIFT; + gp2m_end_index = (gma_end >> FIRST_SHIFT) + 1; + + if ( xen_second_linear_base + gp2m_end_index >= LPAE_ENTRIES * 2 ) + { + dprintk(XENLOG_ERR, "xen second page is small for VLPT for domU"); + return -ENOMEM; + } + + second_lvl_page = alloc_domheap_pages(NULL, 1, 0); + if ( second_lvl_page == NULL ) + return -ENOMEM; + + /* First level p2m is 2 consecutive pages */ + d->arch.dirty.second_lvl[0] = map_domain_page_global( + page_to_mfn(second_lvl_page) ); + d->arch.dirty.second_lvl[1] = map_domain_page_global( + page_to_mfn(second_lvl_page+1) ); + + first[0] = __map_domain_page(p2m->first_level); + first[1] = __map_domain_page(p2m->first_level+1); + + for ( i = gp2m_start_index; i < gp2m_end_index; ++i ) + { + int k = i % LPAE_ENTRIES; + int l = i / LPAE_ENTRIES; + int k2 = (xen_second_linear_base + i) % LPAE_ENTRIES; + int l2 = (xen_second_linear_base + i) / LPAE_ENTRIES; + + write_pte(&xen_second[xen_second_linear_base+i], first[l][k]); + + /* we copy the mapping into domain's structure as a reference + * in case of the context switch (used in restore_vlpt) */ + d->arch.dirty.second_lvl[l2][k2] = first[l][k]; + } + unmap_domain_page(first[0]); + unmap_domain_page(first[1]); + + /* storing the start and end index */ + d->arch.dirty.second_lvl_start = xen_second_linear_base + gp2m_start_index; + d->arch.dirty.second_lvl_end = xen_second_linear_base + gp2m_end_index; + + flush_vlpt(d); + + return 0; +} + +void cleanup_vlpt(struct domain *d) +{ + /* First level p2m is 2 consecutive pages */ + unmap_domain_page_global(d->arch.dirty.second_lvl[0]); + unmap_domain_page_global(d->arch.dirty.second_lvl[1]); +} /* * This function should only be used to remap device address ranges * TODO: add a check to verify this assumption diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h index ef291ff..47d1bce 100644 --- a/xen/include/asm-arm/config.h +++ b/xen/include/asm-arm/config.h @@ -87,6 +87,7 @@ * 0 - 8M <COMMON> * * 32M - 128M Frametable: 24 bytes per page for 16GB of RAM + * 128M - 256M Virtual-linear mapping to P2M table * 256M - 1G VMAP: ioremap and early_ioremap use this virtual address * space * @@ -124,7 +125,9 @@ #define CONFIG_SEPARATE_XENHEAP 1 #define FRAMETABLE_VIRT_START _AT(vaddr_t,0x02000000) +#define VIRT_LIN_P2M_START _AT(vaddr_t,0x08000000) #define VMAP_VIRT_START _AT(vaddr_t,0x10000000) +#define VIRT_LIN_P2M_END VMAP_VIRT_START #define XENHEAP_VIRT_START _AT(vaddr_t,0x40000000) #define XENHEAP_VIRT_END _AT(vaddr_t,0x7fffffff) #define DOMHEAP_VIRT_START _AT(vaddr_t,0x80000000) @@ -157,6 +160,10 @@ #define HYPERVISOR_VIRT_END DIRECTMAP_VIRT_END +/* VIRT_LIN_P2M_START and VIRT_LIN_P2M_END for vlpt */ +#define VIRT_LIN_P2M_START _AT(vaddr_t, 0x08000000) +#define VIRT_LIN_P2M_END VMAP_VIRT_START + #endif /* Fixmap slots */ diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h index 28c359a..5321bd6 100644 --- a/xen/include/asm-arm/domain.h +++ b/xen/include/asm-arm/domain.h @@ -161,6 +161,13 @@ struct arch_domain spinlock_t lock; } vuart; + /* dirty-page tracing */ + struct { + volatile int second_lvl_start; /* for context switch */ + volatile int second_lvl_end; + lpae_t *second_lvl[2]; /* copy of guest p2m's first */ + } dirty; + unsigned int evtchn_irq; } __cacheline_aligned; diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h index 8347524..5fd684f 100644 --- a/xen/include/asm-arm/mm.h +++ b/xen/include/asm-arm/mm.h @@ -4,6 +4,7 @@ #include <xen/config.h> #include <xen/kernel.h> #include <asm/page.h> +#include <asm/config.h> #include <public/xen.h> /* Align Xen to a 2 MiB boundary. */ @@ -342,6 +343,22 @@ static inline void put_page_and_type(struct page_info *page) put_page(page); } +int prepare_vlpt(struct domain *d); +void cleanup_vlpt(struct domain *d); +void restore_vlpt(struct domain *d); + +/* calculate the xen's virtual address for accessing the leaf PTE of + * a given address (GPA) */ +static inline lpae_t * get_vlpt_3lvl_pte(paddr_t addr) +{ + lpae_t *table = (lpae_t *)VIRT_LIN_P2M_START; + + /* Since we slotted the guest's first p2m page table to xen's + * second page table, one shift is enough for calculating the + * index of guest p2m table entry */ + return &table[addr >> PAGE_SHIFT]; +} + #endif /* __ARCH_ARM_MM__ */ /* * Local variables: -- 1.7.9.5 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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