[PATCH kernel 2/2] KVM: PPC: Allow backing bigger guest IOMMU pages with smaller physical pages
Alexey Kardashevskiy
aik at ozlabs.ru
Wed May 2 19:10:56 AEST 2018
On 2/5/18 3:49 pm, David Gibson wrote:
> On Wed, May 02, 2018 at 02:07:23PM +1000, Alexey Kardashevskiy wrote:
>> At the moment we only support in the host the IOMMU page sizes which
>> the guest is aware of, which is 4KB/64KB/16MB. However P9 does not support
>> 16MB IOMMU pages, 2MB and 1GB pages are supported instead. We can still
>> emulate bigger guest pages (for example 16MB) with smaller host pages
>> (4KB/64KB/2MB).
>>
>> This allows the physical IOMMU pages to use a page size smaller or equal
>> than the guest visible IOMMU page size.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>
> Reviewed-by: David Gibson <david at gibson.dropbear.id.au>
>
> Except for one possible nit..
>
>> ---
>> arch/powerpc/kvm/book3s_64_vio.c | 66 +++++++++++++++++++++++++++++--------
>> arch/powerpc/kvm/book3s_64_vio_hv.c | 52 +++++++++++++++++++++++++----
>> 2 files changed, 98 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
>> index 041e54d..e10d6a3 100644
>> --- a/arch/powerpc/kvm/book3s_64_vio.c
>> +++ b/arch/powerpc/kvm/book3s_64_vio.c
>> @@ -176,14 +176,12 @@ extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm, int tablefd,
>>
>> if (!tbltmp)
>> continue;
>> - /*
>> - * Make sure hardware table parameters are exactly the same;
>> - * this is used in the TCE handlers where boundary checks
>> - * use only the first attached table.
>> - */
>> - if ((tbltmp->it_page_shift == stt->page_shift) &&
>> - (tbltmp->it_offset == stt->offset) &&
>> - (tbltmp->it_size == stt->size)) {
>> + /* Make sure hardware table parameters are compatible */
>> + if ((tbltmp->it_page_shift <= stt->page_shift) &&
>> + (tbltmp->it_offset << tbltmp->it_page_shift ==
>> + stt->offset << stt->page_shift) &&
>> + (tbltmp->it_size << tbltmp->it_page_shift ==
>> + stt->size << stt->page_shift)) {
>
> Do we need to worry about stt->offset << stt->page_shift overflowing
> with a buggy or malicious userspace?
I cannot see how it can break anything... But probably some sanity check
that the entire kvmppc_spapr_tce_table fits 64bit would not hurt, I'll make
a separate patch.
>
>> /*
>> * Reference the table to avoid races with
>> * add/remove DMA windows.
>> @@ -396,7 +394,7 @@ static long kvmppc_tce_iommu_mapped_dec(struct kvm *kvm,
>> return H_SUCCESS;
>> }
>>
>> -static long kvmppc_tce_iommu_unmap(struct kvm *kvm,
>> +static long kvmppc_tce_iommu_do_unmap(struct kvm *kvm,
>> struct iommu_table *tbl, unsigned long entry)
>> {
>> enum dma_data_direction dir = DMA_NONE;
>> @@ -416,7 +414,25 @@ static long kvmppc_tce_iommu_unmap(struct kvm *kvm,
>> return ret;
>> }
>>
>> -long kvmppc_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
>> +static long kvmppc_tce_iommu_unmap(struct kvm *kvm,
>> + struct kvmppc_spapr_tce_table *stt, struct iommu_table *tbl,
>> + unsigned long entry)
>> +{
>> + unsigned long ret = H_SUCCESS;
>> + unsigned long subpages = 1ULL << (stt->page_shift - tbl->it_page_shift);
>> + unsigned long io_entry = entry * subpages;
>> + unsigned long subpg;
>> +
>> + for (subpg = 0; subpg < subpages; ++subpg) {
>> + ret = kvmppc_tce_iommu_do_unmap(kvm, tbl, io_entry + subpg);
>> + if (ret != H_SUCCESS)
>> + break;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +long kvmppc_tce_iommu_do_map(struct kvm *kvm, struct iommu_table *tbl,
>> unsigned long entry, unsigned long ua,
>> enum dma_data_direction dir)
>> {
>> @@ -453,6 +469,28 @@ long kvmppc_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
>> return 0;
>> }
>>
>> +static long kvmppc_tce_iommu_map(struct kvm *kvm,
>> + struct kvmppc_spapr_tce_table *stt, struct iommu_table *tbl,
>> + unsigned long entry, unsigned long ua,
>> + enum dma_data_direction dir)
>> +{
>> + unsigned long ret = H_SUCCESS;
>> + unsigned long subpages = 1ULL << (stt->page_shift - tbl->it_page_shift);
>> + unsigned long io_entry = entry * subpages;
>> + unsigned long subpg, pgoff;
>> +
>> + for (subpg = 0, pgoff = 0; subpg < subpages;
>> + ++subpg, pgoff += IOMMU_PAGE_SIZE(tbl)) {
>> +
>> + ret = kvmppc_tce_iommu_do_map(kvm, tbl,
>> + io_entry + subpg, ua + pgoff, dir);
>> + if (ret != H_SUCCESS)
>> + break;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>> unsigned long ioba, unsigned long tce)
>> {
>> @@ -491,10 +529,10 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>>
>> list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>> if (dir == DMA_NONE)
>> - ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
>> + ret = kvmppc_tce_iommu_unmap(vcpu->kvm, stt,
>> stit->tbl, entry);
>> else
>> - ret = kvmppc_tce_iommu_map(vcpu->kvm, stit->tbl,
>> + ret = kvmppc_tce_iommu_map(vcpu->kvm, stt, stit->tbl,
>> entry, ua, dir);
>>
>> if (ret == H_SUCCESS)
>> @@ -570,7 +608,7 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>> return H_PARAMETER;
>>
>> list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>> - ret = kvmppc_tce_iommu_map(vcpu->kvm,
>> + ret = kvmppc_tce_iommu_map(vcpu->kvm, stt,
>> stit->tbl, entry + i, ua,
>> iommu_tce_direction(tce));
>>
>> @@ -618,7 +656,7 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
>> unsigned long entry = ioba >> stt->page_shift;
>>
>> for (i = 0; i < npages; ++i) {
>> - ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
>> + ret = kvmppc_tce_iommu_unmap(vcpu->kvm, stt,
>> stit->tbl, entry + i);
>>
>> if (ret == H_SUCCESS)
>> diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
>> index e220fab..258e786 100644
>> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
>> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
>> @@ -221,7 +221,7 @@ static long kvmppc_rm_tce_iommu_mapped_dec(struct kvm *kvm,
>> return H_SUCCESS;
>> }
>>
>> -static long kvmppc_rm_tce_iommu_unmap(struct kvm *kvm,
>> +static long kvmppc_rm_tce_iommu_do_unmap(struct kvm *kvm,
>> struct iommu_table *tbl, unsigned long entry)
>> {
>> enum dma_data_direction dir = DMA_NONE;
>> @@ -245,7 +245,25 @@ static long kvmppc_rm_tce_iommu_unmap(struct kvm *kvm,
>> return ret;
>> }
>>
>> -static long kvmppc_rm_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
>> +static long kvmppc_rm_tce_iommu_unmap(struct kvm *kvm,
>> + struct kvmppc_spapr_tce_table *stt, struct iommu_table *tbl,
>> + unsigned long entry)
>> +{
>> + unsigned long ret = H_SUCCESS;
>> + unsigned long subpages = 1ULL << (stt->page_shift - tbl->it_page_shift);
>> + unsigned long io_entry = entry * subpages;
>> + unsigned long subpg;
>> +
>> + for (subpg = 0; subpg < subpages; ++subpg) {
>> + ret = kvmppc_rm_tce_iommu_do_unmap(kvm, tbl, io_entry + subpg);
>> + if (ret != H_SUCCESS)
>> + break;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static long kvmppc_rm_tce_iommu_do_map(struct kvm *kvm, struct iommu_table *tbl,
>> unsigned long entry, unsigned long ua,
>> enum dma_data_direction dir)
>> {
>> @@ -290,6 +308,28 @@ static long kvmppc_rm_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
>> return 0;
>> }
>>
>> +static long kvmppc_rm_tce_iommu_map(struct kvm *kvm,
>> + struct kvmppc_spapr_tce_table *stt, struct iommu_table *tbl,
>> + unsigned long entry, unsigned long ua,
>> + enum dma_data_direction dir)
>> +{
>> + unsigned long ret = H_SUCCESS;
>> + unsigned long subpages = 1ULL << (stt->page_shift - tbl->it_page_shift);
>> + unsigned long io_entry = entry * subpages;
>> + unsigned long subpg, pgoff;
>> +
>> + for (subpg = 0, pgoff = 0; subpg < subpages;
>> + ++subpg, pgoff += IOMMU_PAGE_SIZE(tbl)) {
>> +
>> + ret = kvmppc_rm_tce_iommu_do_map(kvm, tbl,
>> + io_entry + subpg, ua + pgoff, dir);
>> + if (ret != H_SUCCESS)
>> + break;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>> unsigned long ioba, unsigned long tce)
>> {
>> @@ -327,10 +367,10 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>>
>> list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>> if (dir == DMA_NONE)
>> - ret = kvmppc_rm_tce_iommu_unmap(vcpu->kvm,
>> + ret = kvmppc_rm_tce_iommu_unmap(vcpu->kvm, stt,
>> stit->tbl, entry);
>> else
>> - ret = kvmppc_rm_tce_iommu_map(vcpu->kvm,
>> + ret = kvmppc_rm_tce_iommu_map(vcpu->kvm, stt,
>> stit->tbl, entry, ua, dir);
>>
>> if (ret == H_SUCCESS)
>> @@ -477,7 +517,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>> return H_PARAMETER;
>>
>> list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>> - ret = kvmppc_rm_tce_iommu_map(vcpu->kvm,
>> + ret = kvmppc_rm_tce_iommu_map(vcpu->kvm, stt,
>> stit->tbl, entry + i, ua,
>> iommu_tce_direction(tce));
>>
>> @@ -529,7 +569,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
>> unsigned long entry = ioba >> stt->page_shift;
>>
>> for (i = 0; i < npages; ++i) {
>> - ret = kvmppc_rm_tce_iommu_unmap(vcpu->kvm,
>> + ret = kvmppc_rm_tce_iommu_unmap(vcpu->kvm, stt,
>> stit->tbl, entry + i);
>>
>> if (ret == H_SUCCESS)
>
--
Alexey
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