linux-kernel - Re: [PATCH v2 4/8] KVM: x86: Add a helper to get the sparse VP

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Date:   Mon, 01 Nov 2021 11:06:14 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ajay Garg <ajaygargnsit@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 4/8] KVM: x86: Add a helper to get the sparse VP_SET
 for IPIs and TLB flushes

Sean Christopherson <seanjc@...gle.com> writes:

> Add a helper, kvm_get_sparse_vp_set(), to handle sanity checks related to
> the VARHEAD field and reading the sparse banks of a VP_SET.  A future
> commit to reduce the memory footprint of sparse_banks will introduce more
> common code to the sparse bank retrieval.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/hyperv.c | 32 ++++++++++++++++----------------
>  1 file changed, 16 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index e68931ed27f6..3d0981163eed 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1750,10 +1750,19 @@ struct kvm_hv_hcall {
>  	sse128_t xmm[HV_HYPERCALL_MAX_XMM_REGISTERS];
>  };
>  
> +static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
> +				 u64 *sparse_banks, gpa_t offset)
> +{
> +	if (hc->var_cnt > 64)
> +		return -EINVAL;
> +
> +	return kvm_read_guest(kvm, hc->ingpa + offset, sparse_banks,
> +			      hc->var_cnt * sizeof(*sparse_banks));
> +}
> +
>  static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool ex)
>  {
>  	int i;
> -	gpa_t gpa;
>  	struct kvm *kvm = vcpu->kvm;
>  	struct hv_tlb_flush_ex flush_ex;
>  	struct hv_tlb_flush flush;
> @@ -1830,13 +1839,9 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
>  			goto do_flush;
>  		}
>  
> -		if (hc->var_cnt > 64)
> -			return HV_STATUS_INVALID_HYPERCALL_INPUT;
> -
> -		gpa = hc->ingpa + offsetof(struct hv_tlb_flush_ex,
> -					   hv_vp_set.bank_contents);
> -		if (unlikely(kvm_read_guest(kvm, gpa, sparse_banks,
> -					    hc->var_cnt * sizeof(sparse_banks[0]))))
> +		if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks,
> +					  offsetof(struct hv_tlb_flush_ex,
> +						   hv_vp_set.bank_contents)))
>  			return HV_STATUS_INVALID_HYPERCALL_INPUT;
>  	}
>  
> @@ -1933,14 +1938,9 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
>  		if (!hc->var_cnt)
>  			goto ret_success;
>  
> -		if (hc->var_cnt > 64)
> -			return HV_STATUS_INVALID_HYPERCALL_INPUT;
> -
> -		if (kvm_read_guest(kvm,
> -				   hc->ingpa + offsetof(struct hv_send_ipi_ex,
> -							vp_set.bank_contents),
> -				   sparse_banks,
> -				   hc->var_cnt * sizeof(sparse_banks[0])))
> +		if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks,
> +					  offsetof(struct hv_send_ipi_ex,
> +						   vp_set.bank_contents)))
>  			return HV_STATUS_INVALID_HYPERCALL_INPUT;
>  	}

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly