Re: [PATCH 23/32] KVM: s390: pci: handle refresh of PCI translations

Matthew Rosato
2021-12-08T18:04:32Z

On 12/8/21 5:30 AM, Niklas Schnelle wrote:
> On Tue, 2021-12-07 at 15:57 -0500, Matthew Rosato wrote:
>> Add a routine that will perform a shadow operation between a guest
>> and host IOAT. A subsequent patch will invoke this in response to
>> an 04 RPCIT instruction intercept.
>>
>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>> ---
>> arch/s390/include/asm/kvm_pci.h | 1 +
>> arch/s390/include/asm/pci_dma.h | 1 +
>> arch/s390/kvm/pci.c | 191 ++++++++++++++++++++++++++++++++
>> arch/s390/kvm/pci.h | 4 +-
>> 4 files changed, 196 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
>> index 254275399f21..97e3a369135d 100644
>> --- a/arch/s390/include/asm/kvm_pci.h
>> +++ b/arch/s390/include/asm/kvm_pci.h
>> @@ -30,6 +30,7 @@ struct kvm_zdev_ioat {
>> struct kvm_zdev {
>> struct zpci_dev *zdev;
>> struct kvm *kvm;
>> + u64 rpcit_count;
>> struct kvm_zdev_ioat ioat;
>> struct zpci_fib fib;
>> };
>> diff --git a/arch/s390/include/asm/pci_dma.h b/arch/s390/include/asm/pci_dma.h
>> index e1d3c1d3fc8a..0ca15e5db3d9 100644
>> --- a/arch/s390/include/asm/pci_dma.h
>> +++ b/arch/s390/include/asm/pci_dma.h
>> @@ -52,6 +52,7 @@ enum zpci_ioat_dtype {
>> #define ZPCI_TABLE_ENTRIES (ZPCI_TABLE_SIZE / ZPCI_TABLE_ENTRY_SIZE)
>> #define ZPCI_TABLE_PAGES (ZPCI_TABLE_SIZE >> PAGE_SHIFT)
>> #define ZPCI_TABLE_ENTRIES_PAGES (ZPCI_TABLE_ENTRIES * ZPCI_TABLE_PAGES)
>> +#define ZPCI_TABLE_ENTRIES_PER_PAGE (ZPCI_TABLE_ENTRIES / ZPCI_TABLE_PAGES)
>>
>> #define ZPCI_TABLE_BITS 11
>> #define ZPCI_PT_BITS 8
>> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
>> index a1c0c0881332..858c5ecdc8b9 100644
>> --- a/arch/s390/kvm/pci.c
>> +++ b/arch/s390/kvm/pci.c
>> @@ -123,6 +123,195 @@ int kvm_s390_pci_aen_init(u8 nisc)
>> return rc;
>> }
>>
>> +static int dma_shadow_cpu_trans(struct kvm_vcpu *vcpu, unsigned long *entry,
>> + unsigned long *gentry)
>> +{
>> + unsigned long idx;
>> + struct page *page;
>> + void *gaddr = NULL;
>> + kvm_pfn_t pfn;
>> + gpa_t addr;
>> + int rc = 0;
>> +
>> + if (pt_entry_isvalid(*gentry)) {
>> + /* pin and validate */
>> + addr = *gentry & ZPCI_PTE_ADDR_MASK;
>> + idx = srcu_read_lock(&vcpu->kvm->srcu);
>> + page = gfn_to_page(vcpu->kvm, gpa_to_gfn(addr));
>> + srcu_read_unlock(&vcpu->kvm->srcu, idx);
>> + if (is_error_page(page))
>> + return -EIO;
>> + gaddr = page_to_virt(page) + (addr & ~PAGE_MASK);
>
> Hmm, this looks like a virtual vs physical address mixup to me that is
> currently not a problem because kernel virtual addresses are equal to
> their physical address. Here page_to_virt(page) gives us a virtual
> address but the entries in the I/O translation table have to be
> physical (aka absolute) addresses.
>
> With my commit "s390/pci: use physical addresses in DMA tables"
> currently in the s390 feature branch this is also reflected in the
> argument types taken by set_pt_pfaa() below so gaddr should have type
> phys_addr_t not void *. That should also remove the need for the cast
> to unsigned long for the duplicate check.

Right... Like the other comment re: virtual vs physical address I will
take a look and fix for v2.