Messages in this thread | | | Date | Mon, 25 Apr 2022 21:09:44 +0200 | Subject | Re: [PATCH v3 07/34] x86/hyperv: Introduce HV_MAX_SPARSE_VCPU_BANKS/HV_VCPUS_PER_SPARSE_BANK constants | From | Christophe JAILLET <> |
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Hi,
Le 14/04/2022 à 15:19, Vitaly Kuznetsov a écrit : > It may not come clear from where the magical '64' value used in > __cpumask_to_vpset() come from. Moreover, '64' means both the maximum > sparse bank number as well as the number of vCPUs per bank. Add defines > to make things clear. These defines are also going to be used by KVM. > > No functional change. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > include/asm-generic/hyperv-tlfs.h | 5 +++++ > include/asm-generic/mshyperv.h | 11 ++++++----- > 2 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h > index fdce7a4cfc6f..020ca9bdbb79 100644 > --- a/include/asm-generic/hyperv-tlfs.h > +++ b/include/asm-generic/hyperv-tlfs.h > @@ -399,6 +399,11 @@ struct hv_vpset { > u64 bank_contents[]; > } __packed; > > +/* The maximum number of sparse vCPU banks which can be encoded by 'struct hv_vpset' */ > +#define HV_MAX_SPARSE_VCPU_BANKS (64) > +/* The number of vCPUs in one sparse bank */ > +#define HV_VCPUS_PER_SPARSE_BANK (64) > + > /* HvCallSendSyntheticClusterIpi hypercall */ > struct hv_send_ipi { > u32 vector; > diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h > index c08758b6b364..0abe91df1ef6 100644 > --- a/include/asm-generic/mshyperv.h > +++ b/include/asm-generic/mshyperv.h > @@ -214,9 +214,10 @@ static inline int __cpumask_to_vpset(struct hv_vpset *vpset, > { > int cpu, vcpu, vcpu_bank, vcpu_offset, nr_bank = 1; > int this_cpu = smp_processor_id(); > + int max_vcpu_bank = hv_max_vp_index / HV_VCPUS_PER_SPARSE_BANK; > > - /* valid_bank_mask can represent up to 64 banks */ > - if (hv_max_vp_index / 64 >= 64) > + /* vpset.valid_bank_mask can represent up to HV_MAX_SPARSE_VCPU_BANKS banks */ > + if (max_vcpu_bank >= HV_MAX_SPARSE_VCPU_BANKS) > return 0; > > /* > @@ -224,7 +225,7 @@ static inline int __cpumask_to_vpset(struct hv_vpset *vpset, > * structs are not cleared between calls, we risk flushing unneeded > * vCPUs otherwise. > */ > - for (vcpu_bank = 0; vcpu_bank <= hv_max_vp_index / 64; vcpu_bank++) > + for (vcpu_bank = 0; vcpu_bank <= max_vcpu_bank; vcpu_bank++) > vpset->bank_contents[vcpu_bank] = 0; > > /* > @@ -236,8 +237,8 @@ static inline int __cpumask_to_vpset(struct hv_vpset *vpset, > vcpu = hv_cpu_number_to_vp_number(cpu); > if (vcpu == VP_INVAL) > return -1; > - vcpu_bank = vcpu / 64; > - vcpu_offset = vcpu % 64; > + vcpu_bank = vcpu / HV_VCPUS_PER_SPARSE_BANK; > + vcpu_offset = vcpu % HV_VCPUS_PER_SPARSE_BANK; > __set_bit(vcpu_offset, (unsigned long *) > &vpset->bank_contents[vcpu_bank]);
Here, we could also use directly: __set_bit(vcpu, vpset->bank_contents);
This is simpler, more readable (IMHO) and also makes 'vcpu_offset' useless. And in case gcc is not able to optimize it by itself, this should also save a few cycles.
Just my 2c, CJ
> if (vcpu_bank >= nr_bank)
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