From: Wei Liu <wei.liu....@gmail.com> On Behalf Of Wei Liu [snip]
> diff --git a/xen/arch/x86/guest/hyperv/util.c > b/xen/arch/x86/guest/hyperv/util.c > new file mode 100644 > index 0000000000..0abb37b05f > --- /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 https://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++ ) > + vpset->bank_contents[vcpu_bank] = 0; > + > + vpset->valid_bank_mask = 0; > + vpset->format = HV_GENERIC_SET_SPARSE_4K; > + > + for_each_cpu ( cpu, mask ) > + { > + unsigned int vcpu = hv_vp_index(cpu); > + > + vcpu_bank = vcpu / 64; > + vcpu_offset = vcpu % 64; > + > + __set_bit(vcpu_offset, &vpset->bank_contents[vcpu_bank]); > + __set_bit(vcpu_bank, &vpset->valid_bank_mask); This approach to setting the bits in the valid_bank_mask causes a bug. If an entire 64-bit word in the bank_contents array is zero because there are no CPUs in that range, the corresponding bit in valid_bank_mask still must be set to tell Hyper-V that the 64-bit word is present in the array and should be processed, even though the content is zero. A zero bit in valid_bank_mask indicates that the corresponding 64-bit word in the array is not present, and every 64-bit word above it has been shifted down. That's why the similar Linux function sets valid_bank_mask the way that it does. Michael > + > + if ( vcpu_bank >= nr ) > + nr = vcpu_bank + 1; > + } > + > + return nr; > +} > + > +/* > + * Local variables: > + * mode: C > + * c-file-style: "BSD" > + * c-basic-offset: 4 > + * tab-width: 4 > + * indent-tabs-mode: nil > + * End: > + */ > -- > 2.20.1 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
