RE: [PATCH v1 14/22] intel_iommu: bind/unbind guest page table to host

["Liu, Yi L" <yi.l.liu@intel.com>]

> From: Peter Xu
> Sent: Wednesday, March 25, 2020 1:47 AM
> To: Liu, Yi L <yi.l.liu@intel.com>
> Subject: Re: [PATCH v1 14/22] intel_iommu: bind/unbind guest page table to host
> 
> On Sun, Mar 22, 2020 at 05:36:11AM -0700, Liu Yi L wrote:
> > This patch captures the guest PASID table entry modifications and
> > propagates the changes to host to setup dual stage DMA translation.
> > The guest page table is configured as 1st level page table (GVA->GPA)
> > whose translation result would further go through host VT-d 2nd level
> > page table(GPA->HPA) under nested translation mode. This is the key
> > part of vSVA support, and also a key to support IOVA over 1st- level
> > page table for Intel VT-d in virtualization environment.
> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Cc: Peter Xu <peterx@redhat.com>
> > Cc: Yi Sun <yi.y.sun@linux.intel.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Richard Henderson <rth@twiddle.net>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > ---
> >  hw/i386/intel_iommu.c          | 98
> +++++++++++++++++++++++++++++++++++++++---
> >  hw/i386/intel_iommu_internal.h | 25 +++++++++++
> >  2 files changed, 118 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c index
> > c985cae..0423c83 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -41,6 +41,7 @@
> >  #include "migration/vmstate.h"
> >  #include "trace.h"
> >  #include "qemu/jhash.h"
> > +#include <linux/iommu.h>
> >
> >  /* context entry operations */
> >  #define VTD_CE_GET_RID2PASID(ce) \
> > @@ -695,6 +696,16 @@ static inline uint16_t
> vtd_pe_get_domain_id(VTDPASIDEntry *pe)
> >      return VTD_SM_PASID_ENTRY_DID((pe)->val[1]);
> >  }
> >
> > +static inline uint32_t vtd_pe_get_fl_aw(VTDPASIDEntry *pe) {
> > +    return 48 + ((pe->val[2] >> 2) & VTD_SM_PASID_ENTRY_FLPM) * 9; }
> > +
> > +static inline dma_addr_t vtd_pe_get_flpt_base(VTDPASIDEntry *pe) {
> > +    return pe->val[2] & VTD_SM_PASID_ENTRY_FLPTPTR; }
> > +
> >  static inline bool vtd_pdire_present(VTDPASIDDirEntry *pdire)  {
> >      return pdire->val & 1;
> > @@ -1856,6 +1867,81 @@ static void
> vtd_context_global_invalidate(IntelIOMMUState *s)
> >      vtd_iommu_replay_all(s);
> >  }
> >
> > +/**
> > + * Caller should hold iommu_lock.
> > + */
> > +static int vtd_bind_guest_pasid(IntelIOMMUState *s, VTDBus *vtd_bus,
> > +                                int devfn, int pasid, VTDPASIDEntry *pe,
> > +                                VTDPASIDOp op) {
> > +    VTDHostIOMMUContext *vtd_dev_icx;
> > +    HostIOMMUContext *host_icx;
> > +    DualIOMMUStage1BindData *bind_data;
> > +    struct iommu_gpasid_bind_data *g_bind_data;
> > +    int ret = -1;
> > +
> > +    vtd_dev_icx = vtd_bus->dev_icx[devfn];
> > +    if (!vtd_dev_icx) {
> > +        return -EINVAL;
> > +    }
> > +
> > +    host_icx = vtd_dev_icx->host_icx;
> > +    if (!host_icx) {
> > +        return -EINVAL;
> > +    }
> > +
> > +    if (!(host_icx->stage1_formats
> > +             & IOMMU_PASID_FORMAT_INTEL_VTD)) {
> > +        error_report_once("IOMMU Stage 1 format is not
> > + compatible!\n");
> 
> Shouldn't we fail with this?

oh, yes. no need to go further though host should also fail it.

> > +    }
> > +
> > +    bind_data = g_malloc0(sizeof(*bind_data));
> > +    bind_data->pasid = pasid;
> > +    g_bind_data = &bind_data->bind_data.gpasid_bind;
> > +
> > +    g_bind_data->flags = 0;
> > +    g_bind_data->vtd.flags = 0;
> > +    switch (op) {
> > +    case VTD_PASID_BIND:
> > +    case VTD_PASID_UPDATE:
> 
> Is VTD_PASID_UPDATE used anywhere?
> 
> But since it's called "UPDATE"... I really want to confirm with you that the bind() to
> the kernel will handle the UPDATE case, right?  I mean, we need to unbind first if
> there is an existing pgtable pointer.

I guess you mean host kernel. right? Actually, it's fine. host kernel
only needs to fill in the latest pgtable pointer and permission configs
to the pasid entry and then issue a cache invalidation. No need to do
unbind firstly since kernel always needs to flush cache after modifying
a pasid entry (includes valid->valid).

> 
> If the answer is yes, then I think we're good, but we really need to comment it
> somewhere about the fact.
> 
> > +        g_bind_data->version = IOMMU_UAPI_VERSION;
> > +        g_bind_data->format = IOMMU_PASID_FORMAT_INTEL_VTD;
> > +        g_bind_data->gpgd = vtd_pe_get_flpt_base(pe);
> > +        g_bind_data->addr_width = vtd_pe_get_fl_aw(pe);
> > +        g_bind_data->hpasid = pasid;
> > +        g_bind_data->gpasid = pasid;
> > +        g_bind_data->flags |= IOMMU_SVA_GPASID_VAL;
> > +        g_bind_data->vtd.flags =
> > +                             (VTD_SM_PASID_ENTRY_SRE_BIT(pe->val[2]) ? 1 : 0)
> > +                           | (VTD_SM_PASID_ENTRY_EAFE_BIT(pe->val[2]) ? 1 : 0)
> > +                           | (VTD_SM_PASID_ENTRY_PCD_BIT(pe->val[1]) ? 1 : 0)
> > +                           | (VTD_SM_PASID_ENTRY_PWT_BIT(pe->val[1]) ? 1 : 0)
> > +                           | (VTD_SM_PASID_ENTRY_EMTE_BIT(pe->val[1]) ? 1 : 0)
> > +                           | (VTD_SM_PASID_ENTRY_CD_BIT(pe->val[1]) ? 1 : 0);
> > +        g_bind_data->vtd.pat = VTD_SM_PASID_ENTRY_PAT(pe->val[1]);
> > +        g_bind_data->vtd.emt = VTD_SM_PASID_ENTRY_EMT(pe->val[1]);
> > +        ret = host_iommu_ctx_bind_stage1_pgtbl(host_icx, bind_data);
> > +        break;
> > +    case VTD_PASID_UNBIND:
> > +        g_bind_data->version = IOMMU_UAPI_VERSION;
> > +        g_bind_data->format = IOMMU_PASID_FORMAT_INTEL_VTD;
> > +        g_bind_data->gpgd = 0;
> > +        g_bind_data->addr_width = 0;
> > +        g_bind_data->hpasid = pasid;
> > +        g_bind_data->gpasid = pasid;
> > +        g_bind_data->flags |= IOMMU_SVA_GPASID_VAL;
> > +        ret = host_iommu_ctx_unbind_stage1_pgtbl(host_icx, bind_data);
> > +        break;
> > +    default:
> > +        error_report_once("Unknown VTDPASIDOp!!!\n");
> > +        break;
> > +    }
> > +
> > +    g_free(bind_data);
> > +
> > +    return ret;
> > +}
> > +
> >  /* Do a context-cache device-selective invalidation.
> >   * @func_mask: FM field after shifting
> >   */
> > @@ -2481,10 +2567,10 @@ static inline void
> > vtd_fill_in_pe_in_cache(IntelIOMMUState *s,
> >
> >      pc_entry->pasid_entry = *pe;
> >      pc_entry->pasid_cache_gen = s->pasid_cache_gen;
> > -    /*
> > -     * TODO:
> > -     * - send pasid bind to host for passthru devices
> > -     */
> > +    vtd_bind_guest_pasid(s, vtd_pasid_as->vtd_bus,
> > +                         vtd_pasid_as->devfn,
> > +                         vtd_pasid_as->pasid,
> > +                         pe, VTD_PASID_BIND);
> >  }
> >
> >  /**
> > @@ -2574,11 +2660,13 @@ static gboolean vtd_flush_pasid(gpointer key,
> gpointer value,
> >       * - when pasid-base-iotlb(piotlb) infrastructure is ready,
> >       *   should invalidate QEMU piotlb togehter with this change.
> >       */
> > +
> >      return false;
> >  remove:
> > +    vtd_bind_guest_pasid(s, vtd_bus, devfn,
> > +                         pasid, NULL, VTD_PASID_UNBIND);
> >      /*
> >       * TODO:
> > -     * - send pasid bind to host for passthru devices
> >       * - when pasid-base-iotlb(piotlb) infrastructure is ready,
> >       *   should invalidate QEMU piotlb togehter with this change.
> >       */
> > diff --git a/hw/i386/intel_iommu_internal.h
> > b/hw/i386/intel_iommu_internal.h index 01fd95c..4451acf 100644
> > --- a/hw/i386/intel_iommu_internal.h
> > +++ b/hw/i386/intel_iommu_internal.h
> > @@ -516,6 +516,20 @@ typedef struct VTDRootEntry VTDRootEntry;
> > #define VTD_SM_CONTEXT_ENTRY_RSVD_VAL0(aw)  (0x1e0ULL |
> ~VTD_HAW_MASK(aw))
> >  #define VTD_SM_CONTEXT_ENTRY_RSVD_VAL1      0xffffffffffe00000ULL
> >
> > +enum VTD_DUAL_STAGE_UAPI {
> > +    UAPI_BIND_GPASID,
> > +    UAPI_NUM
> > +};
> > +typedef enum VTD_DUAL_STAGE_UAPI VTD_DUAL_STAGE_UAPI;
> > +
> > +enum VTDPASIDOp {
> > +    VTD_PASID_BIND,
> > +    VTD_PASID_UNBIND,
> > +    VTD_PASID_UPDATE,
> 
> Same here (whether to drop?).
>
If above reply doesn't make sense, may drop it.

Regards,
Yi Liu