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intel_iommu: support snoop control 

SC is required for some kernel features like vhost-vDPA. So this patch
implements basic SC feature. The idea is pretty simple, for software
emulated DMA it would be always coherent. In this case we can simple
advertise ECAP_SC bit. For VFIO and vhost, thing will be more much
complicated, so this patch simply fail the IOMMU notifier
registration.

In the future, we may want to have a dedicated notifiers flag or
similar mechanism to demonstrate the coherency so VFIO could advertise
that if it has VFIO_DMA_CC_IOMMU, for vhost kernel backend we don't
need that since it's a software backend.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220214060346.72455-1-jasowang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Jason Wang 2022-02-14 14:03:46 +08:00 committed by Michael S. Tsirkin
parent b1f030a0a2
commit b8ffd7d671
3 changed files with 15 additions and 1 deletions
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14
hw/i386/intel_iommu.c
View File

@ -3030,6 +3030,13 @@ static int vtd_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu,
VTDAddressSpace *vtd_as = container_of(iommu, VTDAddressSpace, iommu);
IntelIOMMUState *s = vtd_as->iommu_state;
/* TODO: add support for VFIO and vhost users */
if (s->snoop_control) {
error_setg_errno(errp, -ENOTSUP,
"Snoop Control with vhost or VFIO is not supported");
return -ENOTSUP;
}
/* Update per-address-space notifier flags */
vtd_as->notifier_flags = new;
@ -3113,6 +3120,7 @@ static Property vtd_properties[] = {
VTD_HOST_ADDRESS_WIDTH),
DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode, FALSE),
DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState, scalable_mode, FALSE),
DEFINE_PROP_BOOL("snoop-control", IntelIOMMUState, snoop_control, false),
DEFINE_PROP_BOOL("dma-drain", IntelIOMMUState, dma_drain, true),
DEFINE_PROP_END_OF_LIST(),
};
@ -3643,7 +3651,7 @@ static void vtd_init(IntelIOMMUState *s)
vtd_spte_rsvd_large[3] = VTD_SPTE_LPAGE_L3_RSVD_MASK(s->aw_bits,
x86_iommu->dt_supported);
if (s->scalable_mode) {
if (s->scalable_mode || s->snoop_control) {
vtd_spte_rsvd[1] &= ~VTD_SPTE_SNP;
vtd_spte_rsvd_large[2] &= ~VTD_SPTE_SNP;
vtd_spte_rsvd_large[3] &= ~VTD_SPTE_SNP;
@ -3674,6 +3682,10 @@ static void vtd_init(IntelIOMMUState *s)
s->ecap |= VTD_ECAP_SMTS | VTD_ECAP_SRS | VTD_ECAP_SLTS;
}
if (s->snoop_control) {
s->ecap |= VTD_ECAP_SC;
}
vtd_reset_caches(s);
/* Define registers with default values and bit semantics */

1
hw/i386/intel_iommu_internal.h
View File

@ -188,6 +188,7 @@
#define VTD_ECAP_IR (1ULL << 3)
#define VTD_ECAP_EIM (1ULL << 4)
#define VTD_ECAP_PT (1ULL << 6)
#define VTD_ECAP_SC (1ULL << 7)
#define VTD_ECAP_MHMV (15ULL << 20)
#define VTD_ECAP_SRS (1ULL << 31)
#define VTD_ECAP_SMTS (1ULL << 43)

1
include/hw/i386/intel_iommu.h
View File

@ -228,6 +228,7 @@ struct IntelIOMMUState {
bool caching_mode; /* RO - is cap CM enabled? */
bool scalable_mode; /* RO - is Scalable Mode supported? */
bool snoop_control; /* RO - is SNP filed supported? */
dma_addr_t root; /* Current root table pointer */
bool root_scalable; /* Type of root table (scalable or not) */