[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 3/3] x86/hyperv: L0 assisted TLB flush
On Fri, Feb 14, 2020 at 12:34:30PM +0000, Wei Liu wrote: > Implement L0 assisted TLB flush for Xen on Hyper-V. It takes advantage > of several hypercalls: > > * HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST > * HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX > * HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE > * HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX > > Pick the most efficient hypercalls available. > > Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx> Thanks! LGTM, I've just got a couple of comments below. > --- > v2: > 1. Address Roger and Jan's comments re types etc. > 2. Fix pointer arithmetic. > 3. Misc improvement to code. > --- > xen/arch/x86/guest/hyperv/Makefile | 1 + > xen/arch/x86/guest/hyperv/private.h | 9 ++ > xen/arch/x86/guest/hyperv/tlb.c | 172 +++++++++++++++++++++++++++- > xen/arch/x86/guest/hyperv/util.c | 74 ++++++++++++ > 4 files changed, 255 insertions(+), 1 deletion(-) > create mode 100644 xen/arch/x86/guest/hyperv/util.c > > diff --git a/xen/arch/x86/guest/hyperv/Makefile > b/xen/arch/x86/guest/hyperv/Makefile > index 18902c33e9..0e39410968 100644 > --- a/xen/arch/x86/guest/hyperv/Makefile > +++ b/xen/arch/x86/guest/hyperv/Makefile > @@ -1,2 +1,3 @@ > obj-y += hyperv.o > obj-y += tlb.o > +obj-y += util.o > diff --git a/xen/arch/x86/guest/hyperv/private.h > b/xen/arch/x86/guest/hyperv/private.h > index 509bedaafa..79a77930a0 100644 > --- a/xen/arch/x86/guest/hyperv/private.h > +++ b/xen/arch/x86/guest/hyperv/private.h > @@ -24,12 +24,21 @@ > > #include <xen/cpumask.h> > #include <xen/percpu.h> > +#include <xen/types.h> > > DECLARE_PER_CPU(void *, hv_input_page); > DECLARE_PER_CPU(void *, hv_vp_assist); > DECLARE_PER_CPU(unsigned int, hv_vp_index); > > +static inline unsigned int hv_vp_index(unsigned int cpu) > +{ > + return per_cpu(hv_vp_index, cpu); > +} > + > int hyperv_flush_tlb(const cpumask_t *mask, const void *va, > unsigned int flags); > > +/* Returns number of banks, -ev if error */ > +int cpumask_to_vpset(struct hv_vpset *vpset, const cpumask_t *mask); > + > #endif /* __XEN_HYPERV_PRIVIATE_H__ */ > diff --git a/xen/arch/x86/guest/hyperv/tlb.c b/xen/arch/x86/guest/hyperv/tlb.c > index 48f527229e..f68e14f151 100644 > --- a/xen/arch/x86/guest/hyperv/tlb.c > +++ b/xen/arch/x86/guest/hyperv/tlb.c > @@ -19,15 +19,185 @@ > * Copyright (c) 2020 Microsoft. > */ > > +#include <xen/cpu.h> > #include <xen/cpumask.h> > #include <xen/errno.h> > > +#include <asm/guest/hyperv.h> > +#include <asm/guest/hyperv-hcall.h> > +#include <asm/guest/hyperv-tlfs.h> > + > #include "private.h" > > +/* > + * It is possible to encode up to 4096 pages using the lower 12 bits > + * in an element of gva_list > + */ > +#define HV_TLB_FLUSH_UNIT (4096 * PAGE_SIZE) > + > +static unsigned int fill_gva_list(uint64_t *gva_list, const void *va, > + unsigned int order) > +{ > + unsigned long start = (unsigned long)va; > + unsigned long end = start + (PAGE_SIZE << order) - 1; > + unsigned int n = 0; > + > + do { > + unsigned long remain = end - start; > + > + gva_list[n] = start & PAGE_MASK; > + > + /* > + * Use lower 12 bits to encode the number of additional pages > + * to flush > + */ > + if ( remain >= HV_TLB_FLUSH_UNIT ) > + { > + gva_list[n] |= ~PAGE_MASK; > + start += HV_TLB_FLUSH_UNIT; > + } > + else if ( remain ) remain is always going to be > 0, since the loop condition is end > start, and hence this can be a plain else. > + { > + gva_list[n] |= (remain - 1) >> PAGE_SHIFT; > + start = end; > + } > + > + n++; > + } while ( start < end ); > + > + return n; > +} > + > +static uint64_t flush_tlb_ex(const cpumask_t *mask, const void *va, > + unsigned int flags) > +{ > + struct hv_tlb_flush_ex *flush = this_cpu(hv_input_page); > + int nr_banks; > + unsigned int max_gvas, order = flags & FLUSH_ORDER_MASK; > + uint64_t ret; > + > + if ( !flush || local_irq_is_enabled() ) > + { > + ASSERT_UNREACHABLE(); > + return ~0ULL; > + } > + > + if ( !(ms_hyperv.hints & HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED) ) > + return ~0ULL; > + > + flush->address_space = 0; > + flush->flags = HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES; > + if ( !(flags & FLUSH_TLB_GLOBAL) ) > + flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY; > + > + nr_banks = cpumask_to_vpset(&flush->hv_vp_set, mask); > + if ( nr_banks < 0 ) > + return ~0ULL; It would be nice to propagate the error code from cpumask_to_vpset, but since the function can also return HyperV error codes this doesn't make much sense. > + > + max_gvas = > + (PAGE_SIZE - sizeof(*flush) - nr_banks * > + sizeof(flush->hv_vp_set.bank_contents[0])) / > + sizeof(uint64_t); /* gva is represented as uint64_t */ > + > + /* > + * Flush the entire address space if va is NULL or if there is not > + * enough space for gva_list. > + */ > + if ( !va || (PAGE_SIZE << order) / HV_TLB_FLUSH_UNIT > max_gvas ) > + ret = hv_do_rep_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX, 0, > + nr_banks, virt_to_maddr(flush), 0); You could just return hv_do_rep_hypercall(...); here, which will avoid the else branch below and the indentation. > + else > + { > + uint64_t *gva_list = > + (uint64_t *)flush + sizeof(*flush) / sizeof(uint64_t) + nr_banks; > + unsigned int gvas = fill_gva_list(gva_list, va, order); > + > + BUILD_BUG_ON(sizeof(*flush) % sizeof(uint64_t)); > + > + ret = hv_do_rep_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX, > + gvas, nr_banks, virt_to_maddr(flush), 0); > + } > + > + return ret; > +} > + > int hyperv_flush_tlb(const cpumask_t *mask, const void *va, > unsigned int flags) > { > - return -EOPNOTSUPP; > + unsigned long irq_flags; > + struct hv_tlb_flush *flush = this_cpu(hv_input_page); > + unsigned int max_gvas, order = flags & FLUSH_ORDER_MASK; > + uint64_t ret; > + > + ASSERT(flush); > + ASSERT(!cpumask_empty(mask)); I would also turn this into an if ( ... ) { ASSERT; return -EFOO; } > + > + local_irq_save(irq_flags); > + > + flush->address_space = 0; > + flush->flags = HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES; > + flush->processor_mask = 0; > + if ( !(flags & FLUSH_TLB_GLOBAL) ) > + flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY; > + > + if ( cpumask_equal(mask, &cpu_online_map) ) > + flush->flags |= HV_FLUSH_ALL_PROCESSORS; > + else > + { > + unsigned int cpu; > + > + /* > + * Normally VP indices are in ascending order and match Xen's > + * idea of CPU ids. Check the last index to see if VP index is > + * >= 64. If so, we can skip setting up parameters for > + * non-applicable hypercalls without looking further. > + */ > + if ( hv_vp_index(cpumask_last(mask)) >= 64 ) > + goto do_ex_hypercall; > + > + for_each_cpu ( cpu, mask ) > + { > + uint32_t vpid = hv_vp_index(cpu); This should be unsigned int now. > + > + if ( vpid > ms_hyperv.max_vp_index ) > + { > + local_irq_restore(irq_flags); > + return -ENXIO; > + } > + > + if ( vpid >= 64 ) > + goto do_ex_hypercall; > + > + __set_bit(vpid, &flush->processor_mask); > + } Would it make sense to abstract this as cpumask_to_processor_mask, since you are adding cpumask_to_vpset below. > + } > + > + max_gvas = (PAGE_SIZE - sizeof(*flush)) / sizeof(flush->gva_list[0]); You could init this at declaration, and make it const static since the value can be calculated at compile time AFAICT. Or create a define with it (HV_TLB_FLUSH_MAX_GVAS?). There's no need to store it on the stack. > + > + /* > + * Flush the entire address space if va is NULL or if there is not > + * enough space for gva_list. > + */ > + if ( !va || (PAGE_SIZE << order) / HV_TLB_FLUSH_UNIT > max_gvas ) > + ret = hv_do_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE, > + virt_to_maddr(flush), 0); > + else > + { > + unsigned int gvas = fill_gva_list(flush->gva_list, va, order); No need for the gvas variable, you can just call fill_gva_list at hv_do_rep_hypercall. > + > + ret = hv_do_rep_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST, gvas, 0, > + virt_to_maddr(flush), 0); > + } > + > + goto done; > + > + do_ex_hypercall: > + ret = flush_tlb_ex(mask, va, flags); > + > + done: > + local_irq_restore(irq_flags); > + > + return ret & HV_HYPERCALL_RESULT_MASK ? -ENXIO : 0; > } > > /* > diff --git a/xen/arch/x86/guest/hyperv/util.c > b/xen/arch/x86/guest/hyperv/util.c > new file mode 100644 > index 0000000000..e092593746 > --- /dev/null > +++ b/xen/arch/x86/guest/hyperv/util.c > @@ -0,0 +1,74 @@ > +/****************************************************************************** > + * arch/x86/guest/hyperv/util.c > + * > + * Hyper-V utility functions > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License as published by > + * the Free Software Foundation; either version 2 of the License, or > + * (at your option) any later version. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program; If not, see <http://www.gnu.org/licenses/>. > + * > + * Copyright (c) 2020 Microsoft. > + */ > + > +#include <xen/cpu.h> > +#include <xen/cpumask.h> > +#include <xen/errno.h> > + > +#include <asm/guest/hyperv.h> > +#include <asm/guest/hyperv-tlfs.h> > + > +#include "private.h" > + > +int cpumask_to_vpset(struct hv_vpset *vpset, > + const cpumask_t *mask) > +{ > + int nr = 1; > + unsigned int cpu, vcpu_bank, vcpu_offset; > + unsigned int max_banks = ms_hyperv.max_vp_index / 64; > + > + /* Up to 64 banks can be represented by valid_bank_mask */ > + if ( max_banks >= 64 ) > + return -E2BIG; > + > + /* Clear all banks to avoid flushing unwanted CPUs */ > + for ( vcpu_bank = 0; vcpu_bank <= max_banks; vcpu_bank++ ) I think this is off by one and should be vcpu_bank < max_banks? Or else you are clearing one extra bank. Thanks, Roger. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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