Hi Zhenzhong,
On 2/19/25 9:22 AM, Zhenzhong Duan wrote:
> There are many call sites referencing context entry by calling
> vtd_as_to_context_entry() which will traverse the DMAR table.
didn't you mean vtd_dev_to_context_entry? instead
>
> In most cases we can use cached context entry in vtd_as->context_cache_entry
> except it's stale. Currently only global and domain context invalidation
> stales it.
s/states/stale
Eric
>
> So introduce a helper function vtd_as_to_context_entry() to fetch from cache
> before trying with vtd_dev_to_context_entry().
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
> ---
> hw/i386/intel_iommu.c | 36 +++++++++++++++++++++++-------------
> 1 file changed, 23 insertions(+), 13 deletions(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index df5fb30bc8..7709f55be5 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -1597,6 +1597,22 @@ static int vtd_dev_to_context_entry(IntelIOMMUState
> *s, uint8_t bus_num,
> return 0;
> }
>
> +static int vtd_as_to_context_entry(VTDAddressSpace *vtd_as, VTDContextEntry
> *ce)
> +{
> + IntelIOMMUState *s = vtd_as->iommu_state;
> + uint8_t bus_num = pci_bus_num(vtd_as->bus);
> + uint8_t devfn = vtd_as->devfn;
> + VTDContextCacheEntry *cc_entry = &vtd_as->context_cache_entry;
> +
> + /* Try to fetch context-entry from cache first */
> + if (cc_entry->context_cache_gen == s->context_cache_gen) {
> + *ce = cc_entry->context_entry;
> + return 0;
> + } else {
> + return vtd_dev_to_context_entry(s, bus_num, devfn, ce);
> + }
> +}
> +
> static int vtd_sync_shadow_page_hook(const IOMMUTLBEvent *event,
> void *private)
> {
> @@ -1649,9 +1665,7 @@ static int vtd_address_space_sync(VTDAddressSpace
> *vtd_as)
> return 0;
> }
>
> - ret = vtd_dev_to_context_entry(vtd_as->iommu_state,
> - pci_bus_num(vtd_as->bus),
> - vtd_as->devfn, &ce);
> + ret = vtd_as_to_context_entry(vtd_as, &ce);
> if (ret) {
> if (ret == -VTD_FR_CONTEXT_ENTRY_P) {
> /*
> @@ -1710,8 +1724,7 @@ static bool vtd_as_pt_enabled(VTDAddressSpace *as)
> assert(as);
>
> s = as->iommu_state;
> - if (vtd_dev_to_context_entry(s, pci_bus_num(as->bus), as->devfn,
> - &ce)) {
> + if (vtd_as_to_context_entry(as, &ce)) {
> /*
> * Possibly failed to parse the context entry for some reason
> * (e.g., during init, or any guest configuration errors on
> @@ -2443,8 +2456,7 @@ static void vtd_iotlb_domain_invalidate(IntelIOMMUState
> *s, uint16_t domain_id)
> vtd_iommu_unlock(s);
>
> QLIST_FOREACH(vtd_as, &s->vtd_as_with_notifiers, next) {
> - if (!vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus),
> - vtd_as->devfn, &ce) &&
> + if (!vtd_as_to_context_entry(vtd_as, &ce) &&
> domain_id == vtd_get_domain_id(s, &ce, vtd_as->pasid)) {
> vtd_address_space_sync(vtd_as);
> }
> @@ -2466,8 +2478,7 @@ static void
> vtd_iotlb_page_invalidate_notify(IntelIOMMUState *s,
> hwaddr size = (1 << am) * VTD_PAGE_SIZE;
>
> QLIST_FOREACH(vtd_as, &(s->vtd_as_with_notifiers), next) {
> - ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus),
> - vtd_as->devfn, &ce);
> + ret = vtd_as_to_context_entry(vtd_as, &ce);
> if (!ret && domain_id == vtd_get_domain_id(s, &ce, vtd_as->pasid)) {
> uint32_t rid2pasid = PCI_NO_PASID;
>
> @@ -2974,8 +2985,7 @@ static void vtd_piotlb_pasid_invalidate(IntelIOMMUState
> *s,
> vtd_iommu_unlock(s);
>
> QLIST_FOREACH(vtd_as, &s->vtd_as_with_notifiers, next) {
> - if (!vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus),
> - vtd_as->devfn, &ce) &&
> + if (!vtd_as_to_context_entry(vtd_as, &ce) &&
> domain_id == vtd_get_domain_id(s, &ce, vtd_as->pasid)) {
> uint32_t rid2pasid = VTD_CE_GET_RID2PASID(&ce);
>
> @@ -4154,7 +4164,7 @@ static void
> vtd_report_ir_illegal_access(VTDAddressSpace *vtd_as,
> assert(vtd_as->pasid != PCI_NO_PASID);
>
> /* Try out best to fetch FPD, we can't do anything more */
> - if (vtd_dev_to_context_entry(s, bus_n, vtd_as->devfn, &ce) == 0) {
> + if (vtd_as_to_context_entry(vtd_as, &ce) == 0) {
> is_fpd_set = ce.lo & VTD_CONTEXT_ENTRY_FPD;
> if (!is_fpd_set && s->root_scalable) {
> vtd_ce_get_pasid_fpd(s, &ce, &is_fpd_set, vtd_as->pasid);
> @@ -4491,7 +4501,7 @@ static void vtd_iommu_replay(IOMMUMemoryRegion
> *iommu_mr, IOMMUNotifier *n)
> /* replay is protected by BQL, page walk will re-setup it safely */
> iova_tree_remove(vtd_as->iova_tree, map);
>
> - if (vtd_dev_to_context_entry(s, bus_n, vtd_as->devfn, &ce) == 0) {
> + if (vtd_as_to_context_entry(vtd_as, &ce) == 0) {
> trace_vtd_replay_ce_valid(s->root_scalable ? "scalable mode" :
> "legacy mode",
> bus_n, PCI_SLOT(vtd_as->devfn),
