Re: [PATCH v2 4/8] KVM: x86: Add a helper to get the sparse VP_SET for IPIs and TLB flushes

From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-hyperv@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ajay Garg <ajaygargnsit@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v2 4/8] KVM: x86: Add a helper to get the sparse VP_SET for IPIs and TLB flushes
Date: Mon, 01 Nov 2021 11:06:14 +0100	[thread overview]
Message-ID: <874k8wkx61.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20211030000800.3065132-5-seanjc@google.com>

Sean Christopherson <seanjc@google.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@google.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@redhat.com>

-- 
Vitaly