Re: [Qemu-devel] [PATCH v3 2/2] intel-iommu: extend VTD emulation to allow 57-bit IOVA address width.

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Dec 18, 2018 at 06:01:16PM +0800, Yu Zhang wrote:
> On Tue, Dec 18, 2018 at 05:47:14PM +0800, Yu Zhang wrote:
> > On Mon, Dec 17, 2018 at 02:29:02PM +0100, Igor Mammedov wrote:
> > > On Wed, 12 Dec 2018 21:05:39 +0800
> > > Yu Zhang <yu.c.zhang@linux.intel.com> wrote:
> > > 
> > > > A 5-level paging capable VM may choose to use 57-bit IOVA address width.
> > > > E.g. guest applications may prefer to use its VA as IOVA when performing
> > > > VFIO map/unmap operations, to avoid the burden of managing the IOVA space.
> > > > 
> > > > This patch extends the current vIOMMU logic to cover the extended address
> > > > width. When creating a VM with 5-level paging feature, one can choose to
> > > > create a virtual VTD with 5-level paging capability, with configurations
> > > > like "-device intel-iommu,x-aw-bits=57".
> > > > 
> > > > Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> > > > Reviewed-by: Peter Xu <peterx@redhat.com>
> > > > ---
> > > > Cc: "Michael S. Tsirkin" <mst@redhat.com>
> > > > Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> > > > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > > > Cc: Richard Henderson <rth@twiddle.net>
> > > > Cc: Eduardo Habkost <ehabkost@redhat.com>
> > > > Cc: Peter Xu <peterx@redhat.com>
> > > > ---
> > > >  hw/i386/intel_iommu.c          | 53 ++++++++++++++++++++++++++++++++----------
> > > >  hw/i386/intel_iommu_internal.h | 10 ++++++--
> > > >  include/hw/i386/intel_iommu.h  |  1 +
> > > >  3 files changed, 50 insertions(+), 14 deletions(-)
> > > > 
> > > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > > > index 0e88c63..871110c 100644
> > > > --- a/hw/i386/intel_iommu.c
> > > > +++ b/hw/i386/intel_iommu.c
> > > > @@ -664,16 +664,16 @@ static inline bool vtd_iova_range_check(uint64_t iova, VTDContextEntry *ce,
> > > >  
> > > >  /*
> > > >   * Rsvd field masks for spte:
> > > > - *     Index [1] to [4] 4k pages
> > > > - *     Index [5] to [8] large pages
> > > > + *     Index [1] to [5] 4k pages
> > > > + *     Index [6] to [10] large pages
> > > >   */
> > > > -static uint64_t vtd_paging_entry_rsvd_field[9];
> > > > +static uint64_t vtd_paging_entry_rsvd_field[11];
> > > >  
> > > >  static bool vtd_slpte_nonzero_rsvd(uint64_t slpte, uint32_t level)
> > > >  {
> > > >      if (slpte & VTD_SL_PT_PAGE_SIZE_MASK) {
> > > >          /* Maybe large page */
> > > > -        return slpte & vtd_paging_entry_rsvd_field[level + 4];
> > > > +        return slpte & vtd_paging_entry_rsvd_field[level + 5];
> > > >      } else {
> > > >          return slpte & vtd_paging_entry_rsvd_field[level];
> > > >      }
> > > > @@ -3127,6 +3127,8 @@ static void vtd_init(IntelIOMMUState *s)
> > > >               VTD_CAP_SAGAW_39bit | VTD_CAP_MGAW(s->aw_bits);
> > > >      if (s->aw_bits == VTD_AW_48BIT) {
> > > >          s->cap |= VTD_CAP_SAGAW_48bit;
> > > > +    } else if (s->aw_bits == VTD_AW_57BIT) {
> > > > +        s->cap |= VTD_CAP_SAGAW_57bit | VTD_CAP_SAGAW_48bit;
> > > >      }
> > > >      s->ecap = VTD_ECAP_QI | VTD_ECAP_IRO;
> > > >      s->haw_bits = cpu->phys_bits;
> > > > @@ -3139,10 +3141,12 @@ static void vtd_init(IntelIOMMUState *s)
> > > >      vtd_paging_entry_rsvd_field[2] = VTD_SPTE_PAGE_L2_RSVD_MASK(s->haw_bits);
> > > >      vtd_paging_entry_rsvd_field[3] = VTD_SPTE_PAGE_L3_RSVD_MASK(s->haw_bits);
> > > >      vtd_paging_entry_rsvd_field[4] = VTD_SPTE_PAGE_L4_RSVD_MASK(s->haw_bits);
> > > > -    vtd_paging_entry_rsvd_field[5] = VTD_SPTE_LPAGE_L1_RSVD_MASK(s->haw_bits);
> > > > -    vtd_paging_entry_rsvd_field[6] = VTD_SPTE_LPAGE_L2_RSVD_MASK(s->haw_bits);
> > > > -    vtd_paging_entry_rsvd_field[7] = VTD_SPTE_LPAGE_L3_RSVD_MASK(s->haw_bits);
> > > > -    vtd_paging_entry_rsvd_field[8] = VTD_SPTE_LPAGE_L4_RSVD_MASK(s->haw_bits);
> > > > +    vtd_paging_entry_rsvd_field[5] = VTD_SPTE_PAGE_L5_RSVD_MASK(s->haw_bits);
> > > > +    vtd_paging_entry_rsvd_field[6] = VTD_SPTE_LPAGE_L1_RSVD_MASK(s->haw_bits);
> > > > +    vtd_paging_entry_rsvd_field[7] = VTD_SPTE_LPAGE_L2_RSVD_MASK(s->haw_bits);
> > > > +    vtd_paging_entry_rsvd_field[8] = VTD_SPTE_LPAGE_L3_RSVD_MASK(s->haw_bits);
> > > > +    vtd_paging_entry_rsvd_field[9] = VTD_SPTE_LPAGE_L4_RSVD_MASK(s->haw_bits);
> > > > +    vtd_paging_entry_rsvd_field[10] = VTD_SPTE_LPAGE_L5_RSVD_MASK(s->haw_bits);
> > > >  
> > > >      if (x86_iommu->intr_supported) {
> > > >          s->ecap |= VTD_ECAP_IR | VTD_ECAP_MHMV;
> > > > @@ -3241,6 +3245,23 @@ static AddressSpace *vtd_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
> > > >      return &vtd_as->as;
> > > >  }
> > > >  
> > > > +static bool host_has_la57(void)
> > > > +{
> > > > +    uint32_t ecx, unused;
> > > > +
> > > > +    host_cpuid(7, 0, &unused, &unused, &ecx, &unused);
> > > > +    return ecx & CPUID_7_0_ECX_LA57;
> > > > +}
> > > > +
> > > > +static bool guest_has_la57(void)
> > > > +{
> > > > +    CPUState *cs = first_cpu;
> > > > +    X86CPU *cpu = X86_CPU(cs);
> > > > +    CPUX86State *env = &cpu->env;
> > > > +
> > > > +    return env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_LA57;
> > > > +}
> > > another direct access to CPU fields,
> > > I'd suggest to set this value when iommu is created
> > > i.e. add 'la57' property and set from iommu owner.
> > > 
> > 
> > Sorry, do you mean "-device intel-iommu,la57"? I think we do not need
> > that, because a 5-level capable vIOMMU can be created with properties
> > like "-device intel-iommu,x-aw-bits=57". 
> > 
> > The guest CPU fields are checked to make sure the VM has LA57 CPU feature,
> > because I believe there shall be no 5-level IOMMU on platforms without LA57
> > CPUs. 

I don't necessarily see why these need to be connected.
If yes pls add code to explain.


> > > >  static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
> > > >  {
> > > >      X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(s);
> > > > @@ -3267,11 +3288,19 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
> > > >          }
> > > >      }
> > > >  
> > > > -    /* Currently only address widths supported are 39 and 48 bits */
> > > > +    /* Currently address widths supported are 39, 48, and 57 bits */
> > > >      if ((s->aw_bits != VTD_AW_39BIT) &&
> > > > -        (s->aw_bits != VTD_AW_48BIT)) {
> > > > -        error_setg(errp, "Supported values for x-aw-bits are: %d, %d",
> > > > -                   VTD_AW_39BIT, VTD_AW_48BIT);
> > > > +        (s->aw_bits != VTD_AW_48BIT) &&
> > > > +        (s->aw_bits != VTD_AW_57BIT)) {
> > > > +        error_setg(errp, "Supported values for x-aw-bits are: %d, %d, %d",
> > > > +                   VTD_AW_39BIT, VTD_AW_48BIT, VTD_AW_57BIT);
> > > > +        return false;
> > > > +    }
> > > > +
> > > > +    if ((s->aw_bits == VTD_AW_57BIT) &&
> > > > +        !(host_has_la57() && guest_has_la57())) {
> > > Does iommu supposed to work in TCG mode?
> > > If yes then why it should care about host_has_la57()?
> > > 
> > 
> > Hmm... I did not take TCG mode into consideration. And host_has_la57() is
> > used to guarantee the host have la57 feature so that iommu shadowing works
> > for device assignment.
> > 
> > I guess iommu shall work in TCG mode(though I am not quite sure about this).
> > But I do not have any usage case of a 5-level vIOMMU in TCG in mind. So maybe
> > we can:
> > 1> check the 'ms->accel' in vtd_decide_config() and do not care about host
> > capability if it is TCG.
> 
> For choice 1, kvm_enabled() might be used instead of ms->accel. Thanks Peter
> for the remind. :)


This needs a big comment with an explanation though.
And probably a TODO to make it work under TCG ...

> > 2> Or, we can choose to keep as it is, and add the check when 5-level paging
> > vIOMMU does have usage in TCG?
> > 
> > But as to the check of guest capability, I still believe it is necessary. As
> > said, a VM without LA57 feature shall not see a VT-d with 5-level IOMMU.
> > 
> > > > +        error_setg(errp, "Do not support 57-bit DMA address, unless both "
> > > > +                         "host and guest are capable of 5-level paging");
> > > >          return false;
> > > >      }
> > > >  
> > > > diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> > > > index d084099..2b29b6f 100644
> > > > --- a/hw/i386/intel_iommu_internal.h
> > > > +++ b/hw/i386/intel_iommu_internal.h
> > > > @@ -114,8 +114,8 @@
> > > >                                       VTD_INTERRUPT_ADDR_FIRST + 1)
> > > >  
> > > >  /* The shift of source_id in the key of IOTLB hash table */
> > > > -#define VTD_IOTLB_SID_SHIFT         36
> > > > -#define VTD_IOTLB_LVL_SHIFT         52
> > > > +#define VTD_IOTLB_SID_SHIFT         45
> > > > +#define VTD_IOTLB_LVL_SHIFT         61
> > > >  #define VTD_IOTLB_MAX_SIZE          1024    /* Max size of the hash table */
> > > >  
> > > >  /* IOTLB_REG */
> > > > @@ -212,6 +212,8 @@
> > > >  #define VTD_CAP_SAGAW_39bit         (0x2ULL << VTD_CAP_SAGAW_SHIFT)
> > > >   /* 48-bit AGAW, 4-level page-table */
> > > >  #define VTD_CAP_SAGAW_48bit         (0x4ULL << VTD_CAP_SAGAW_SHIFT)
> > > > + /* 57-bit AGAW, 5-level page-table */
> > > > +#define VTD_CAP_SAGAW_57bit         (0x8ULL << VTD_CAP_SAGAW_SHIFT)
> > > >  
> > > >  /* IQT_REG */
> > > >  #define VTD_IQT_QT(val)             (((val) >> 4) & 0x7fffULL)
> > > > @@ -379,6 +381,8 @@ typedef union VTDInvDesc VTDInvDesc;
> > > >          (0x800ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > >  #define VTD_SPTE_PAGE_L4_RSVD_MASK(aw) \
> > > >          (0x880ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > > +#define VTD_SPTE_PAGE_L5_RSVD_MASK(aw) \
> > > > +        (0x880ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > >  #define VTD_SPTE_LPAGE_L1_RSVD_MASK(aw) \
> > > >          (0x800ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > >  #define VTD_SPTE_LPAGE_L2_RSVD_MASK(aw) \
> > > > @@ -387,6 +391,8 @@ typedef union VTDInvDesc VTDInvDesc;
> > > >          (0x3ffff800ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > >  #define VTD_SPTE_LPAGE_L4_RSVD_MASK(aw) \
> > > >          (0x880ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > > +#define VTD_SPTE_LPAGE_L5_RSVD_MASK(aw) \
> > > > +        (0x880ULL | ~(VTD_HAW_MASK(aw) | VTD_SL_IGN_COM))
> > > >  
> > > >  /* Information about page-selective IOTLB invalidate */
> > > >  struct VTDIOTLBPageInvInfo {
> > > > diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> > > > index 820451c..7474c4f 100644
> > > > --- a/include/hw/i386/intel_iommu.h
> > > > +++ b/include/hw/i386/intel_iommu.h
> > > > @@ -49,6 +49,7 @@
> > > >  #define DMAR_REG_SIZE               0x230
> > > >  #define VTD_AW_39BIT                39
> > > >  #define VTD_AW_48BIT                48
> > > > +#define VTD_AW_57BIT                57
> > > >  #define VTD_ADDRESS_WIDTH           VTD_AW_39BIT
> > > >  #define VTD_HAW_MASK(aw)            ((1ULL << (aw)) - 1)
> > > >  
> > > 
> > > 
> > 
> > B.R.
> > Yu
> >