[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC v2 4/6] xen/arm: Implement VLPT for guest p2m mapping in live migration
On 15/04/2014 22:05, Wei Huang wrote: > 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; > + alloc_domain_struct() clears the domain page before handing it back. Initialising things like this to 0 is pointless. > 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, This is taking a volatile int, shifting left by 21 and then using it as a virtual address. It is going to do the wrong thing more often than the right thing. second_lvl_{start,end} should be unsigned long, and I cant see a justification for why they should be volatile. > + 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; These are all array indices - they should all be unsigned, as should the loop variable. > + > + 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); shifted int as virtual address. Also, SECOND_SIZE exists. > + } > + } > + > + 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); unsigned int held in signed integer value. > + > + 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); Xen style - spaces immediately surrounding binary operators. ~Andrew > + > + 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: _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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