Re: [PATCH kernel v3 2/7] KVM: PPC: Rework H_PUT_TCE/H_GET_TCE handlers

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Feb 15, 2016 at 12:55:04PM +1100, Alexey Kardashevskiy wrote:
> This reworks the existing H_PUT_TCE/H_GET_TCE handlers to have following
> patches applied nicer.
> 
> This moves the ioba boundaries check to a helper and adds a check for
> least bits which have to be zeros.
> 
> The patch is pretty mechanical (only check for least ioba bits is added)
> so no change in behaviour is expected.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
> Changelog:
> v3:
> * moved list_for_each_entry_lockless() to the next patch
> * added overflow check in kvmppc_ioba_validate() as H_STUFF_TCE handles
> more than just 512 TCEs at once
> 
> v2:
> * compare @ret with H_SUCCESS instead of assuming H_SUCCESS is zero
> * made error reporting cleaner
> ---
>  arch/powerpc/kvm/book3s_64_vio_hv.c | 109 +++++++++++++++++++++++-------------
>  1 file changed, 71 insertions(+), 38 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
> index 89e96b3..f29ba2c 100644
> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> @@ -35,71 +35,104 @@
>  #include <asm/ppc-opcode.h>
>  #include <asm/kvm_host.h>
>  #include <asm/udbg.h>
> +#include <asm/iommu.h>
>  
>  #define TCES_PER_PAGE	(PAGE_SIZE / sizeof(u64))
>  
> +/*
> + * Finds a TCE table descriptor by LIOBN.
> + *
> + * WARNING: This will be called in real or virtual mode on HV KVM and virtual
> + *          mode on PR KVM
> + */
> +static struct kvmppc_spapr_tce_table *kvmppc_find_table(struct kvm_vcpu *vcpu,
> +		unsigned long liobn)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvmppc_spapr_tce_table *stt;
> +
> +	list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list)
> +		if (stt->liobn == liobn)
> +			return stt;
> +
> +	return NULL;
> +}
> +
> +/*
> + * Validates IO address.
> + *
> + * WARNING: This will be called in real-mode on HV KVM and virtual
> + *          mode on PR KVM
> + */
> +static long kvmppc_ioba_validate(struct kvmppc_spapr_tce_table *stt,
> +		unsigned long ioba, unsigned long npages)
> +{
> +	unsigned long mask = (1ULL << IOMMU_PAGE_SHIFT_4K) - 1;
> +	unsigned long idx = ioba >> IOMMU_PAGE_SHIFT_4K;
> +	unsigned long size = stt->window_size >> IOMMU_PAGE_SHIFT_4K;
> +
> +	if ((ioba & mask) || (idx + npages > size) || (idx + npages < idx))
> +		return H_PARAMETER;
> +
> +	return H_SUCCESS;
> +}
> +
>  /* WARNING: This will be called in real-mode on HV KVM and virtual
>   *          mode on PR KVM
>   */
>  long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  		      unsigned long ioba, unsigned long tce)
>  {
> -	struct kvm *kvm = vcpu->kvm;
> -	struct kvmppc_spapr_tce_table *stt;
> +	struct kvmppc_spapr_tce_table *stt = kvmppc_find_table(vcpu, liobn);
> +	long ret;
> +	unsigned long idx;
> +	struct page *page;
> +	u64 *tbl;
>  
>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
>  	/* 	    liobn, ioba, tce); */
>  
> -	list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) {
> -		if (stt->liobn == liobn) {
> -			unsigned long idx = ioba >> SPAPR_TCE_SHIFT;
> -			struct page *page;
> -			u64 *tbl;
> +	if (!stt)
> +		return H_TOO_HARD;
>  
> -			/* udbg_printf("H_PUT_TCE: liobn 0x%lx => stt=%p  window_size=0x%x\n", */
> -			/* 	    liobn, stt, stt->window_size); */
> -			if (ioba >= stt->window_size)
> -				return H_PARAMETER;
> +	ret = kvmppc_ioba_validate(stt, ioba, 1);
> +	if (ret != H_SUCCESS)
> +		return ret;
>  
> -			page = stt->pages[idx / TCES_PER_PAGE];
> -			tbl = (u64 *)page_address(page);
> +	idx = ioba >> SPAPR_TCE_SHIFT;
> +	page = stt->pages[idx / TCES_PER_PAGE];
> +	tbl = (u64 *)page_address(page);
>  
> -			/* FIXME: Need to validate the TCE itself */
> -			/* udbg_printf("tce @ %p\n", &tbl[idx % TCES_PER_PAGE]); */
> -			tbl[idx % TCES_PER_PAGE] = tce;
> -			return H_SUCCESS;
> -		}
> -	}
> +	/* FIXME: Need to validate the TCE itself */
> +	/* udbg_printf("tce @ %p\n", &tbl[idx % TCES_PER_PAGE]); */
> +	tbl[idx % TCES_PER_PAGE] = tce;
>  
> -	/* Didn't find the liobn, punt it to userspace */
> -	return H_TOO_HARD;
> +	return H_SUCCESS;
>  }
>  EXPORT_SYMBOL_GPL(kvmppc_h_put_tce);
>  
>  long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  		      unsigned long ioba)
>  {
> -	struct kvm *kvm = vcpu->kvm;
> -	struct kvmppc_spapr_tce_table *stt;
> +	struct kvmppc_spapr_tce_table *stt = kvmppc_find_table(vcpu, liobn);
> +	long ret;
> +	unsigned long idx;
> +	struct page *page;
> +	u64 *tbl;
>  
> -	list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) {
> -		if (stt->liobn == liobn) {
> -			unsigned long idx = ioba >> SPAPR_TCE_SHIFT;
> -			struct page *page;
> -			u64 *tbl;
> +	if (!stt)
> +		return H_TOO_HARD;
>  
> -			if (ioba >= stt->window_size)
> -				return H_PARAMETER;
> +	ret = kvmppc_ioba_validate(stt, ioba, 1);
> +	if (ret != H_SUCCESS)
> +		return ret;
>  
> -			page = stt->pages[idx / TCES_PER_PAGE];
> -			tbl = (u64 *)page_address(page);
> +	idx = ioba >> SPAPR_TCE_SHIFT;
> +	page = stt->pages[idx / TCES_PER_PAGE];
> +	tbl = (u64 *)page_address(page);
>  
> -			vcpu->arch.gpr[4] = tbl[idx % TCES_PER_PAGE];
> -			return H_SUCCESS;
> -		}
> -	}
> +	vcpu->arch.gpr[4] = tbl[idx % TCES_PER_PAGE];
>  
> -	/* Didn't find the liobn, punt it to userspace */
> -	return H_TOO_HARD;
> +	return H_SUCCESS;
>  }
>  EXPORT_SYMBOL_GPL(kvmppc_h_get_tce);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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