On 7/8/25 1:05 PM, Zhenzhong Duan wrote:
> This adds an new entry VTDPASIDCacheEntry in VTDAddressSpace to cache the
> pasid entry and track PASID usage and future PASID tagged DMA address
> translation support in vIOMMU.
>
> VTDAddressSpace of PCI_NO_PASID is allocated when device is plugged and
> never freed. For other pasid, VTDAddressSpace instance is created/destroyed
> per the guest pasid entry set up/destroy.
>
> When guest modifies a PASID entry, QEMU will capture the guest pasid selective
> pasid cache invalidation, allocate or remove a VTDAddressSpace instance per
> the
> invalidation reasons:
>
> a) a present pasid entry moved to non-present
> b) a present pasid entry to be a present entry
> c) a non-present pasid entry moved to present
>
> This patch handles a) and b), following patch will handle c).
>
> vIOMMU emulator could figure out the reason by fetching latest guest pasid
> entry
> and compare it with cached PASID entry.
>
> Signed-off-by: Yi Liu
> Signed-off-by: Yi Sun
> Signed-off-by: Zhenzhong Duan
> ---
> hw/i386/intel_iommu.c | 194 +++--
> hw/i386/intel_iommu_internal.h | 27 -
> hw/i386/trace-events | 3 +
> include/hw/i386/intel_iommu.h | 6 +
> 4 files changed, 218 insertions(+), 12 deletions(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 38e7f7b7be..5bda439de6 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -1675,7 +1675,7 @@ static uint16_t vtd_get_domain_id(IntelIOMMUState *s,
>
> if (s->root_scalable) {
> vtd_ce_get_pasid_entry(s, ce, &pe, pasid);
> -return VTD_SM_PASID_ENTRY_DID(pe.val[1]);
> +return VTD_SM_PASID_ENTRY_DID(&pe);
> }
>
> return VTD_CONTEXT_ENTRY_DID(ce->hi);
> @@ -3103,6 +3103,181 @@ static bool vtd_process_piotlb_desc(IntelIOMMUState
> *s,
> return true;
> }
>
> +static inline int vtd_dev_get_pe_from_pasid(VTDAddressSpace *vtd_as,
> +uint32_t pasid, VTDPASIDEntry
> *pe)
> +{
> +IntelIOMMUState *s = vtd_as->iommu_state;
> +VTDContextEntry ce;
> +int ret;
> +
> +if (!s->root_scalable) {
> +return -VTD_FR_RTADDR_INV_TTM;
> +}
> +
> +ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus),
> vtd_as->devfn,
> + &ce);
> +if (ret) {
> +return ret;
> +}
> +
> +return vtd_ce_get_pasid_entry(s, &ce, pe, pasid);
> +}
> +
> +static bool vtd_pasid_entry_compare(VTDPASIDEntry *p1, VTDPASIDEntry *p2)
> +{
> +return !memcmp(p1, p2, sizeof(*p1));
> +}
> +
> +/*
> + * This function is used to update or clear cached pasid entry in vtd_as.
> + * vtd_as is released when corresponding cached pasid entry is cleared,
> + * except for PCI_NO_PASID which vtd_as is owen by PCI sub-system.
I would document when it is supposed to return true (indicates that the
cached pasid entry needs to be removed).
> + */
> +static gboolean vtd_flush_pasid_locked(gpointer key, gpointer value,
> + gpointer user_data)
> +{
> +VTDPASIDCacheInfo *pc_info = user_data;
> +VTDAddressSpace *vtd_as = value;
> +VTDPASIDCacheEntry *pc_entry = &vtd_as->pasid_cache_entry;
> +VTDPASIDEntry pe;
> +uint16_t did;
> +uint32_t pasid;
> +int ret;
> +
> +if (!pc_entry->valid) {
> +return false;
> +}
> +did = VTD_SM_PASID_ENTRY_DID(&pc_entry->pasid_entry);
> +
> +if (vtd_as_to_iommu_pasid_locked(vtd_as, &pasid)) {
> +goto remove;
> +}
> +
> +switch (pc_info->type) {
> +case VTD_PASID_CACHE_PASIDSI:
> +if (pc_info->pasid != pasid) {
> +return false;
> +}
> +/* fall through */
> +case VTD_PASID_CACHE_DOMSI:
> +if (pc_info->did != did) {
> +return false;
> +}
> +/* fall through */
> +case VTD_PASID_CACHE_GLOBAL_INV:
> +break;
> +default:
> +error_setg(&error_fatal, "invalid pc_info->type for flush");
> +}
> +
> +/*
> + * pasid cache invalidation may indicate a present pasid
> + * entry to present pasid entry modification. To cover such
> + * case, vIOMMU emulator needs to fetch latest guest pasid
> + * entry and compares with cached pasid entry, then update
> + * pasid cache.
> + */
> +ret = vtd_dev_get_pe_from_pasid(vtd_as, pasid, &pe);
> +if (ret) {
> +/*
> + * No valid pasid entry in guest memory. e.g. pasid entry
> + * was modified to be either all-zero or non-present. Either
> + * case means existing pasid cache should be removed.
> + */
> +goto remove;
> +}
> +
> +/* No need to update if cached pasid entry is latest */
that comment sounds really weird to me. In case the cache entry does not
match the one in guest mem, you update it below - at least that's what I
understand ;-) - However you want to retur
