Subject: Re: [PATCH kernel 8/9] KVM: PPC: Add in-kernel handling for VFIO

From: David Gibson <[email-masked]>
Date: Tue, 8 Mar 2016 22:08:12 +1100

On Mon, Mar 07, 2016 at 02:41:16PM +1100, Alexey Kardashevskiy wrote:
> This allows the host kernel to handle H_PUT_TCE, H_PUT_TCE_INDIRECT
> and H_STUFF_TCE requests targeted an IOMMU TCE table used for VFIO
> without passing them to user space which saves time on switching
> to user space and back.
> 
> Both real and virtual modes are supported. The kernel tries to
> handle a TCE request in the real mode, if fails it passes the request
> to the virtual mode to complete the operation. If it a virtual mode
> handler fails, the request is passed to user space; this is not expected
> to happen ever though.

Well... not expect to happen with a qemu which uses this.  Presumably
it will fall back to userspace routinely if you have an old qemu that
doesn't add the liobn mappings.

> The first user of this is VFIO on POWER. Trampolines to the VFIO external
> user API functions are required for this patch.

I'm not sure what you mean by "trampoline" here.

> This uses a VFIO KVM device to associate a logical bus number (LIOBN)
> with an VFIO IOMMU group fd and enable in-kernel handling of map/unmap
> requests.

Group fd?  Or container fd?  The group fd wouldn't make a lot of
sense.

> To make use of the feature, the user space has to create a guest view
> of the TCE table via KVM_CAP_SPAPR_TCE/KVM_CAP_SPAPR_TCE_64 and
> then associate a LIOBN with this table via VFIO KVM device,
> a KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE_LIOBN property (which is added in
> the next patch).
> 
> Tests show that this patch increases transmission speed from 220MB/s
> to 750..1020MB/s on 10Gb network (Chelsea CXGB3 10Gb ethernet card).

Is that with or without DDW (i.e. with or without a 64-bit DMA window)?

> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
>  arch/powerpc/kvm/book3s_64_vio.c    | 184 +++++++++++++++++++++++++++++++++++
>  arch/powerpc/kvm/book3s_64_vio_hv.c | 186 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 370 insertions(+)
> 
> diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
> index 7965fc7..9417d12 100644
> --- a/arch/powerpc/kvm/book3s_64_vio.c
> +++ b/arch/powerpc/kvm/book3s_64_vio.c
> @@ -33,6 +33,7 @@
>  #include <asm/kvm_ppc.h>
>  #include <asm/kvm_book3s.h>
>  #include <asm/mmu-hash64.h>
> +#include <asm/mmu_context.h>
>  #include <asm/hvcall.h>
>  #include <asm/synch.h>
>  #include <asm/ppc-opcode.h>
> @@ -317,11 +318,161 @@ fail:
>  	return ret;
>  }
>  
> +static long kvmppc_tce_iommu_mapped_dec(struct iommu_table *tbl,
> +		unsigned long entry)
> +{
> +	struct mm_iommu_table_group_mem_t *mem = NULL;
> +	const unsigned long pgsize = 1ULL << tbl->it_page_shift;
> +	unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> +
> +	if (!pua)
> +		return H_HARDWARE;
> +
> +	mem = mm_iommu_lookup(*pua, pgsize);
> +	if (!mem)
> +		return H_HARDWARE;
> +
> +	mm_iommu_mapped_dec(mem);
> +
> +	*pua = 0;
> +
> +	return H_SUCCESS;
> +}
> +
> +static long kvmppc_tce_iommu_unmap(struct iommu_table *tbl,
> +		unsigned long entry)
> +{
> +	enum dma_data_direction dir = DMA_NONE;
> +	unsigned long hpa = 0;
> +
> +	if (iommu_tce_xchg(tbl, entry, &hpa, &dir))
> +		return H_HARDWARE;
> +
> +	if (dir == DMA_NONE)
> +		return H_SUCCESS;
> +
> +	return kvmppc_tce_iommu_mapped_dec(tbl, entry);
> +}
> +
> +long kvmppc_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
> +		unsigned long entry, unsigned long gpa,
> +		enum dma_data_direction dir)
> +{
> +	long ret;
> +	unsigned long hpa, ua, *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> +	struct mm_iommu_table_group_mem_t *mem;
> +
> +	if (!pua)
> +		return H_HARDWARE;

H_HARDWARE?  Or H_PARAMETER?  This essentially means the guest has
supplied a bad physical address, doesn't it?

> +	if (kvmppc_gpa_to_ua(kvm, gpa, &ua, NULL))
> +		return H_HARDWARE;
> +
> +	mem = mm_iommu_lookup(ua, 1ULL << tbl->it_page_shift);
> +	if (!mem)
> +		return H_HARDWARE;
> +
> +	if (mm_iommu_ua_to_hpa(mem, ua, &hpa))
> +		return H_HARDWARE;
> +
> +	if (mm_iommu_mapped_inc(mem))
> +		return H_HARDWARE;
> +
> +	ret = iommu_tce_xchg(tbl, entry, &hpa, &dir);
> +	if (ret) {
> +		mm_iommu_mapped_dec(mem);
> +		return H_TOO_HARD;
> +	}
> +
> +	if (dir != DMA_NONE)
> +		kvmppc_tce_iommu_mapped_dec(tbl, entry);
> +
> +	*pua = ua;

IIUC this means you have a copy of the UA for every group attached to
the TCE table, but they'll all be the same.  Any way to avoid that
duplication?

> +	return 0;
> +}
> +
> +long kvmppc_h_put_tce_iommu(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl,
> +		unsigned long liobn, unsigned long ioba,
> +		unsigned long tce)
> +{
> +	long idx, ret = H_HARDWARE;
> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> +	const unsigned long gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +	const enum dma_data_direction dir = iommu_tce_direction(tce);
> +
> +	/* Clear TCE */
> +	if (dir == DMA_NONE) {
> +		if (iommu_tce_clear_param_check(tbl, ioba, 0, 1))
> +			return H_PARAMETER;
> +
> +		return kvmppc_tce_iommu_unmap(tbl, entry);
> +	}
> +
> +	/* Put TCE */
> +	if (iommu_tce_put_param_check(tbl, ioba, tce))
> +		return H_PARAMETER;
> +
> +	idx = srcu_read_lock(&vcpu->kvm->srcu);
> +	ret = kvmppc_tce_iommu_map(vcpu->kvm, tbl, entry, gpa, dir);
> +	srcu_read_unlock(&vcpu->kvm->srcu, idx);
> +
> +	return ret;
> +}
> +
> +static long kvmppc_h_put_tce_indirect_iommu(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl, unsigned long ioba,
> +		u64 __user *tces, unsigned long npages)
> +{
> +	unsigned long i, ret, tce, gpa;
> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> +
> +	for (i = 0; i < npages; ++i) {
> +		gpa = be64_to_cpu(tces[i]) & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> +		if (iommu_tce_put_param_check(tbl, ioba +
> +				(i << tbl->it_page_shift), gpa))
> +			return H_PARAMETER;
> +	}
> +
> +	for (i = 0; i < npages; ++i) {
> +		tce = be64_to_cpu(tces[i]);

tces is a user address, which means it should only be dereferenced via
get_user() or copy_from_user() helpers.

> +		gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> +		ret = kvmppc_tce_iommu_map(vcpu->kvm, tbl, entry + i, gpa,
> +				iommu_tce_direction(tce));
> +		if (ret != H_SUCCESS)
> +			return ret;
> +	}
> +
> +	return H_SUCCESS;
> +}
> +
> +long kvmppc_h_stuff_tce_iommu(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl,
> +		unsigned long liobn, unsigned long ioba,
> +		unsigned long tce_value, unsigned long npages)
> +{
> +	unsigned long i;
> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> +
> +	if (iommu_tce_clear_param_check(tbl, ioba, tce_value, npages))
> +		return H_PARAMETER;
> +
> +	for (i = 0; i < npages; ++i)
> +		kvmppc_tce_iommu_unmap(tbl, entry + i);
> +
> +	return H_SUCCESS;
> +}
> +
>  long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  		      unsigned long ioba, unsigned long tce)
>  {
>  	struct kvmppc_spapr_tce_table *stt = kvmppc_find_table(vcpu, liobn);
>  	long ret;
> +	struct kvmppc_spapr_tce_group *kg;
> +	struct iommu_table *tbltmp = NULL;
>  
>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
>  	/* 	    liobn, ioba, tce); */
> @@ -337,6 +488,15 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  	if (ret != H_SUCCESS)
>  		return ret;
>  
> +	list_for_each_entry_lockless(kg, &stt->groups, next) {
> +		if (kg->tbl == tbltmp)
> +			continue;
> +		tbltmp = kg->tbl;
> +		ret = kvmppc_h_put_tce_iommu(vcpu, kg->tbl, liobn, ioba, tce);
> +		if (ret != H_SUCCESS)
> +			return ret;
> +	}
> +
>  	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
>  
>  	return H_SUCCESS;
> @@ -351,6 +511,8 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  	long i, ret = H_SUCCESS, idx;
>  	unsigned long entry, ua = 0;
>  	u64 __user *tces, tce;
> +	struct kvmppc_spapr_tce_group *kg;
> +	struct iommu_table *tbltmp = NULL;
>  
>  	stt = kvmppc_find_table(vcpu, liobn);
>  	if (!stt)
> @@ -378,6 +540,16 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  	}
>  	tces = (u64 __user *) ua;
>  
> +	list_for_each_entry_lockless(kg, &stt->groups, next) {
> +		if (kg->tbl == tbltmp)
> +			continue;
> +		tbltmp = kg->tbl;
> +		ret = kvmppc_h_put_tce_indirect_iommu(vcpu,
> +				kg->tbl, ioba, tces, npages);
> +		if (ret != H_SUCCESS)
> +			goto unlock_exit;
> +	}
> +
>  	for (i = 0; i < npages; ++i) {
>  		if (get_user(tce, tces + i)) {
>  			ret = H_TOO_HARD;
> @@ -405,6 +577,8 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
>  {
>  	struct kvmppc_spapr_tce_table *stt;
>  	long i, ret;
> +	struct kvmppc_spapr_tce_group *kg;
> +	struct iommu_table *tbltmp = NULL;
>  
>  	stt = kvmppc_find_table(vcpu, liobn);
>  	if (!stt)
> @@ -418,6 +592,16 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
>  	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
>  		return H_PARAMETER;
>  
> +	list_for_each_entry_lockless(kg, &stt->groups, next) {
> +		if (kg->tbl == tbltmp)
> +			continue;
> +		tbltmp = kg->tbl;
> +		ret = kvmppc_h_stuff_tce_iommu(vcpu, kg->tbl, liobn, ioba,
> +				tce_value, npages);
> +		if (ret != H_SUCCESS)
> +			return ret;
> +	}
> +
>  	for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift))
>  		kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value);
>  
> diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
> index 11163ae..6567d6c 100644
> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> @@ -26,6 +26,7 @@
>  #include <linux/slab.h>
>  #include <linux/hugetlb.h>
>  #include <linux/list.h>
> +#include <linux/iommu.h>
>  
>  #include <asm/tlbflush.h>
>  #include <asm/kvm_ppc.h>
> @@ -212,11 +213,162 @@ static struct mm_iommu_table_group_mem_t *kvmppc_rm_iommu_lookup(
>  	return mm_iommu_lookup_rm(mm, ua, size);
>  }
>  
> +static long kvmppc_rm_tce_iommu_mapped_dec(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl, unsigned long entry)
> +{
> +	struct mm_iommu_table_group_mem_t *mem = NULL;
> +	const unsigned long pgsize = 1ULL << tbl->it_page_shift;
> +	unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> +
> +	if (!pua)
> +		return H_SUCCESS;
> +
> +	pua = (void *) vmalloc_to_phys(pua);
> +	if (!pua)
> +		return H_SUCCESS;
> +
> +	mem = kvmppc_rm_iommu_lookup(vcpu, *pua, pgsize);
> +	if (!mem)
> +		return H_HARDWARE;
> +
> +	mm_iommu_mapped_dec(mem);
> +
> +	*pua = 0;
> +
> +	return H_SUCCESS;
> +}
> +
> +static long kvmppc_rm_tce_iommu_unmap(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl, unsigned long entry)
> +{
> +	enum dma_data_direction dir = DMA_NONE;
> +	unsigned long hpa = 0;
> +
> +	if (iommu_tce_xchg_rm(tbl, entry, &hpa, &dir))
> +		return H_HARDWARE;
> +
> +	if (dir == DMA_NONE)
> +		return H_SUCCESS;
> +
> +	return kvmppc_rm_tce_iommu_mapped_dec(vcpu, tbl, entry);
> +}
> +
> +long kvmppc_rm_tce_iommu_map(struct kvm_vcpu *vcpu, struct iommu_table *tbl,
> +		unsigned long entry, unsigned long gpa,
> +		enum dma_data_direction dir)
> +{
> +	long ret;
> +	unsigned long hpa = 0, ua;
> +	unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> +	struct mm_iommu_table_group_mem_t *mem;
> +
> +	if (kvmppc_gpa_to_ua(vcpu->kvm, gpa, &ua, NULL))
> +		return H_HARDWARE;
> +	mem = kvmppc_rm_iommu_lookup(vcpu, ua, 1ULL << tbl->it_page_shift);
> +	if (!mem)
> +		return H_HARDWARE;
> +
> +	if (mm_iommu_rm_ua_to_hpa(mem, ua, &hpa))
> +		return H_HARDWARE;
> +
> +	pua = (void *) vmalloc_to_phys(pua);
> +	if (!pua)
> +		return H_HARDWARE;
> +
> +	if (mm_iommu_mapped_inc(mem))
> +		return H_HARDWARE;
> +
> +	ret = iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
> +	if (ret) {
> +		mm_iommu_mapped_dec(mem);
> +		return H_TOO_HARD;
> +	}
> +
> +	if (dir != DMA_NONE)
> +		kvmppc_rm_tce_iommu_mapped_dec(vcpu, tbl, entry);
> +
> +	*pua = ua;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvmppc_rm_tce_iommu_map);
> +
> +static long kvmppc_rm_h_put_tce_iommu(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl, unsigned long liobn,
> +		unsigned long ioba, unsigned long tce)
> +{
> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> +	const unsigned long gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +	const enum dma_data_direction dir = iommu_tce_direction(tce);
> +
> +	/* Clear TCE */
> +	if (dir == DMA_NONE) {
> +		if (iommu_tce_clear_param_check(tbl, ioba, 0, 1))
> +			return H_PARAMETER;
> +
> +		return kvmppc_rm_tce_iommu_unmap(vcpu, tbl, entry);
> +	}
> +
> +	/* Put TCE */
> +	if (iommu_tce_put_param_check(tbl, ioba, gpa))
> +		return H_PARAMETER;
> +
> +	return kvmppc_rm_tce_iommu_map(vcpu, tbl, entry, gpa, dir);
> +}
> +
> +static long kvmppc_rm_h_put_tce_indirect_iommu(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl, unsigned long ioba,
> +		u64 *tces, unsigned long npages)
> +{
> +	unsigned long i, ret, tce, gpa;
> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> +
> +	for (i = 0; i < npages; ++i) {
> +		gpa = be64_to_cpu(tces[i]) & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> +		if (iommu_tce_put_param_check(tbl, ioba +
> +				(i << tbl->it_page_shift), gpa))
> +			return H_PARAMETER;
> +	}
> +
> +	for (i = 0; i < npages; ++i) {
> +		tce = be64_to_cpu(tces[i]);
> +		gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> +		ret = kvmppc_rm_tce_iommu_map(vcpu, tbl, entry + i, gpa,
> +				iommu_tce_direction(tce));
> +		if (ret != H_SUCCESS)
> +			return ret;
> +	}
> +
> +	return H_SUCCESS;
> +}
> +
> +static long kvmppc_rm_h_stuff_tce_iommu(struct kvm_vcpu *vcpu,
> +		struct iommu_table *tbl,
> +		unsigned long liobn, unsigned long ioba,
> +		unsigned long tce_value, unsigned long npages)
> +{
> +	unsigned long i;
> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> +
> +	if (iommu_tce_clear_param_check(tbl, ioba, tce_value, npages))
> +		return H_PARAMETER;
> +
> +	for (i = 0; i < npages; ++i)
> +		kvmppc_rm_tce_iommu_unmap(vcpu, tbl, entry + i);
> +
> +	return H_SUCCESS;
> +}
> +
>  long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  		unsigned long ioba, unsigned long tce)
>  {
>  	struct kvmppc_spapr_tce_table *stt = kvmppc_find_table(vcpu, liobn);
>  	long ret;
> +	struct kvmppc_spapr_tce_group *kg;
> +	struct iommu_table *tbltmp = NULL;
>  
>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
>  	/* 	    liobn, ioba, tce); */
> @@ -232,6 +384,16 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  	if (ret != H_SUCCESS)
>  		return ret;
>  
> +	list_for_each_entry_lockless(kg, &stt->groups, next) {
> +		if (kg->tbl == tbltmp)
> +			continue;
> +		tbltmp = kg->tbl;
> +		ret = kvmppc_rm_h_put_tce_iommu(vcpu, kg->tbl,
> +				liobn, ioba, tce);
> +		if (ret != H_SUCCESS)
> +			return ret;
> +	}
> +
>  	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
>  
>  	return H_SUCCESS;
> @@ -272,6 +434,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  	long i, ret = H_SUCCESS;
>  	unsigned long tces, entry, ua = 0;
>  	unsigned long *rmap = NULL;
> +	struct iommu_table *tbltmp = NULL;
>  
>  	stt = kvmppc_find_table(vcpu, liobn);
>  	if (!stt)
> @@ -299,6 +462,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  		 * depend on hpt.
>  		 */
>  		struct mm_iommu_table_group_mem_t *mem;
> +		struct kvmppc_spapr_tce_group *kg;
>  
>  		if (kvmppc_gpa_to_ua(vcpu->kvm, tce_list, &ua, NULL))
>  			return H_TOO_HARD;
> @@ -306,6 +470,16 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  		mem = kvmppc_rm_iommu_lookup(vcpu, ua, IOMMU_PAGE_SIZE_4K);
>  		if (!mem || mm_iommu_rm_ua_to_hpa(mem, ua, &tces))
>  			return H_TOO_HARD;
> +
> +		list_for_each_entry_lockless(kg, &stt->groups, next) {
> +			if (kg->tbl == tbltmp)
> +				continue;
> +			tbltmp = kg->tbl;
> +			ret = kvmppc_rm_h_put_tce_indirect_iommu(vcpu,
> +					kg->tbl, ioba, (u64 *)tces, npages);
> +			if (ret != H_SUCCESS)
> +				return ret;
> +		}
>  	} else {
>  		/*
>  		 * This is emulated devices case.
> @@ -355,6 +529,8 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
>  {
>  	struct kvmppc_spapr_tce_table *stt;
>  	long i, ret;
> +	struct kvmppc_spapr_tce_group *kg;
> +	struct iommu_table *tbltmp = NULL;
>  
>  	stt = kvmppc_find_table(vcpu, liobn);
>  	if (!stt)
> @@ -368,6 +544,16 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
>  	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
>  		return H_PARAMETER;
>  
> +	list_for_each_entry_lockless(kg, &stt->groups, next) {
> +		if (kg->tbl == tbltmp)
> +			continue;
> +		tbltmp = kg->tbl;
> +		ret = kvmppc_rm_h_stuff_tce_iommu(vcpu, kg->tbl,
> +				liobn, ioba, tce_value, npages);
> +		if (ret != H_SUCCESS)
> +			return ret;
> +	}
> +
>  	for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift))
>  		kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value);
>  

-- 
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