Re: [PATCH v3 12/17] intel_iommu: Add support for PASID-based device IOTLB invalidation

[Jason Wang]

On Mon, Dec 16, 2024 at 4:22 PM Duan, Zhenzhong
<zhenzhong.duan@intel.com> wrote:
>
>
>
> >-----Original Message-----
> >From: Jason Wang <jasowang@redhat.com>
> >Sent: Sunday, September 29, 2024 9:59 AM
> >Subject: Re: [PATCH v3 12/17] intel_iommu: Add support for PASID-based device
> >IOTLB invalidation
> >
> >On Fri, Sep 27, 2024 at 3:18 PM Duan, Zhenzhong
> ><zhenzhong.duan@intel.com> wrote:
> >>
> >>
> >>
> >> >-----Original Message-----
> >> >From: Jason Wang <jasowang@redhat.com>
> >> >Subject: Re: [PATCH v3 12/17] intel_iommu: Add support for PASID-based
> >> >device IOTLB invalidation
> >> >
> >> >On Wed, Sep 11, 2024 at 1:27 PM Zhenzhong Duan
> >> ><zhenzhong.duan@intel.com> wrote:
> >> >>
> >> >> From: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> >> >>
> >> >> Signed-off-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> >> >> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> >> >> ---
> >> >>  hw/i386/intel_iommu_internal.h | 11 ++++++++
> >> >>  hw/i386/intel_iommu.c          | 50
> >> >++++++++++++++++++++++++++++++++++
> >> >>  2 files changed, 61 insertions(+)
> >> >>
> >> >> diff --git a/hw/i386/intel_iommu_internal.h
> >> >b/hw/i386/intel_iommu_internal.h
> >> >> index 4f2c3a9350..52bdbf3bc5 100644
> >> >> --- a/hw/i386/intel_iommu_internal.h
> >> >> +++ b/hw/i386/intel_iommu_internal.h
> >> >> @@ -375,6 +375,7 @@ typedef union VTDInvDesc VTDInvDesc;
> >> >>  #define VTD_INV_DESC_WAIT               0x5 /* Invalidation Wait 
> >> >> Descriptor
> >> >*/
> >> >>  #define VTD_INV_DESC_PIOTLB             0x6 /* PASID-IOTLB Invalidate 
> >> >> Desc
> >> >*/
> >> >>  #define VTD_INV_DESC_PC                 0x7 /* PASID-cache Invalidate 
> >> >> Desc */
> >> >> +#define VTD_INV_DESC_DEV_PIOTLB         0x8 /* PASID-based-DIOTLB
> >> >inv_desc*/
> >> >>  #define VTD_INV_DESC_NONE               0   /* Not an Invalidate 
> >> >> Descriptor
> >> >*/
> >> >>
> >> >>  /* Masks for Invalidation Wait Descriptor*/
> >> >> @@ -413,6 +414,16 @@ typedef union VTDInvDesc VTDInvDesc;
> >> >>  #define VTD_INV_DESC_DEVICE_IOTLB_RSVD_HI 0xffeULL
> >> >>  #define VTD_INV_DESC_DEVICE_IOTLB_RSVD_LO 0xffff0000ffe0fff8
> >> >>
> >> >> +/* Mask for PASID Device IOTLB Invalidate Descriptor */
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_ADDR(val) ((val) & \
> >> >> +                                                   
> >> >> 0xfffffffffffff000ULL)
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_SIZE(val) ((val >> 11) & 0x1)
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_GLOBAL(val) ((val) & 0x1)
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_SID(val) (((val) >> 16) &
> >> >0xffffULL)
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_PASID(val) ((val >> 32) &
> >> >0xfffffULL)
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_RSVD_HI 0x7feULL
> >> >> +#define VTD_INV_DESC_PASID_DEVICE_IOTLB_RSVD_LO
> >> >0xfff000000000f000ULL
> >> >> +
> >> >>  /* Rsvd field masks for spte */
> >> >>  #define VTD_SPTE_SNP 0x800ULL
> >> >>
> >> >> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> >> >> index d28c862598..4cf56924e1 100644
> >> >> --- a/hw/i386/intel_iommu.c
> >> >> +++ b/hw/i386/intel_iommu.c
> >> >> @@ -3017,6 +3017,49 @@ static void
> >> >do_invalidate_device_tlb(VTDAddressSpace *vtd_dev_as,
> >> >>      memory_region_notify_iommu(&vtd_dev_as->iommu, 0, event);
> >> >>  }
> >> >>
> >> >> +static bool vtd_process_device_piotlb_desc(IntelIOMMUState *s,
> >> >> +                                           VTDInvDesc *inv_desc)
> >> >> +{
> >> >> +    uint16_t sid;
> >> >> +    VTDAddressSpace *vtd_dev_as;
> >> >> +    bool size;
> >> >> +    bool global;
> >> >> +    hwaddr addr;
> >> >> +    uint32_t pasid;
> >> >> +
> >> >> +    if ((inv_desc->hi & VTD_INV_DESC_PASID_DEVICE_IOTLB_RSVD_HI) ||
> >> >> +         (inv_desc->lo & VTD_INV_DESC_PASID_DEVICE_IOTLB_RSVD_LO)) {
> >> >> +        error_report_once("%s: invalid pasid-based dev iotlb inv desc:"
> >> >> +                          "hi=%"PRIx64 "(reserved nonzero)",
> >> >> +                          __func__, inv_desc->hi);
> >> >> +        return false;
> >> >> +    }
> >> >> +
> >> >> +    global = VTD_INV_DESC_PASID_DEVICE_IOTLB_GLOBAL(inv_desc->hi);
> >> >> +    size = VTD_INV_DESC_PASID_DEVICE_IOTLB_SIZE(inv_desc->hi);
> >> >> +    addr = VTD_INV_DESC_PASID_DEVICE_IOTLB_ADDR(inv_desc->hi);
> >> >> +    sid = VTD_INV_DESC_PASID_DEVICE_IOTLB_SID(inv_desc->lo);
> >> >> +    if (global) {
> >> >> +        QLIST_FOREACH(vtd_dev_as, &s->vtd_as_with_notifiers, next) {
> >> >> +            if ((vtd_dev_as->pasid != PCI_NO_PASID) &&
> >> >> +                (PCI_BUILD_BDF(pci_bus_num(vtd_dev_as->bus),
> >> >> +                                           vtd_dev_as->devfn) == sid)) 
> >> >> {
> >> >> +                do_invalidate_device_tlb(vtd_dev_as, size, addr);
> >> >> +            }
> >> >> +        }
> >> >> +    } else {
> >> >> +        pasid = VTD_INV_DESC_PASID_DEVICE_IOTLB_PASID(inv_desc->lo);
> >> >> +        vtd_dev_as = vtd_get_as_by_sid_and_pasid(s, sid, pasid);
> >> >> +        if (!vtd_dev_as) {
> >> >> +            return true;
> >> >> +        }
> >> >> +
> >> >> +        do_invalidate_device_tlb(vtd_dev_as, size, addr);
> >> >
> >> >Question:
> >> >
> >> >I wonder if current vhost (which has a device IOTLB abstraction via
> >> >virtio-pci) can work with this (PASID based IOTLB invalidation)
> >>
> >> Currently, it depends on if caching-mode is on. If it's off, vhost works. 
> >> E.g.:
> >>
> >> -device intel-iommu,caching-mode=off,dma-drain=on,device-iotlb=on,x-
> >scalable-mode=on
> >> -netdev tap,id=tap0,vhost=on,script=/etc/qemu-ifup
> >> -device virtio-net-pci,netdev=tap0,bus=root0,iommu_platform=on,ats=on
> >>
> >> It doesn't work currently when caching-mode is on.
> >> Reason is linux kernel has an optimization to send only piotlb 
> >> invalidation,
> >> no device-piotlb invalidation is sent. But I heard from Yi the optimization
> >> will be dropped, then it will work too when caching-mode is on.
> >
> >Great, if possible please copy me when sending those fixes.
>
> FYI, I just found the optimization had already been dropped since April 2024 
> by commit 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=304b3bde24b58515a75fd198beb52ca57df6275f
>
> After updating guest kernel to a new version containing above commit,
> vhost works irrespective the value of caching-mode.
>
> Thanks
> Zhenzhong

Great. Thanks for the updating.