From ed90f91b61844abd2dff2eb970f721a6cf072235 Mon Sep 17 00:00:00 2001

From: Matthew Rosato <mjrosato@linux.ibm.com>

Date: Fri, 28 Oct 2022 15:47:57 -0400

Subject: [PATCH 6/9] s390x/pci: coalesce unmap operations

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RH-Author: Cédric Le Goater <clg@redhat.com>

RH-MergeRequest: 141: s390x/pci: reset ISM passthrough devices on shutdown and system reset

RH-Bugzilla: 2163701

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Cornelia Huck <cohuck@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

RH-Commit: [1/3] 80c3a2c1d720057ae2a80b338ea06c9c6c804532 (clegoate/qemu-kvm-c9s)

Currently, each unmapped page is handled as an individual iommu

region notification.  Attempt to group contiguous unmap operations

into fewer notifications to reduce overhead.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>

Message-Id: <20221028194758.204007-3-mjrosato@linux.ibm.com>

Reviewed-by: Eric Farman <farman@linux.ibm.com>

Signed-off-by: Thomas Huth <thuth@redhat.com>

(cherry picked from commit ef536007c3301bbd6a787e4c2210ea289adaa6f0)

Signed-off-by: Cédric Le Goater <clg@redhat.com>

---

 hw/s390x/s390-pci-inst.c | 51 ++++++++++++++++++++++++++++++++++++++++

 1 file changed, 51 insertions(+)

diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c

index 7cc4bcf850..66e764f901 100644

--- a/hw/s390x/s390-pci-inst.c

+++ b/hw/s390x/s390-pci-inst.c

@@ -640,6 +640,8 @@ static uint32_t s390_pci_update_iotlb(S390PCIIOMMU *iommu,

         }

         g_hash_table_remove(iommu->iotlb, &entry->iova);

         inc_dma_avail(iommu);

+        /* Don't notify the iommu yet, maybe we can bundle contiguous unmaps */

+        goto out;

     } else {

         if (cache) {

             if (cache->perm == entry->perm &&

@@ -663,15 +665,44 @@ static uint32_t s390_pci_update_iotlb(S390PCIIOMMU *iommu,

         dec_dma_avail(iommu);

     }

+    /*

+     * All associated iotlb entries have already been cleared, trigger the

+     * unmaps.

+     */

     memory_region_notify_iommu(&iommu->iommu_mr, 0, event);

 out:

     return iommu->dma_limit ? iommu->dma_limit->avail : 1;

 }

+static void s390_pci_batch_unmap(S390PCIIOMMU *iommu, uint64_t iova,

+                                 uint64_t len)

+{

+    uint64_t remain = len, start = iova, end = start + len - 1, mask, size;

+    IOMMUTLBEvent event = {

+        .type = IOMMU_NOTIFIER_UNMAP,

+        .entry = {

+            .target_as = &address_space_memory,

+            .translated_addr = 0,

+            .perm = IOMMU_NONE,

+        },

+    };

+

+    while (remain >= TARGET_PAGE_SIZE) {

+        mask = dma_aligned_pow2_mask(start, end, 64);

+        size = mask + 1;

+        event.entry.iova = start;

+        event.entry.addr_mask = mask;

+        memory_region_notify_iommu(&iommu->iommu_mr, 0, event);

+        start += size;

+        remain -= size;

+    }

+}

+

 int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t r2, uintptr_t ra)

 {

     CPUS390XState *env = &cpu->env;

+    uint64_t iova, coalesce = 0;

     uint32_t fh;

     uint16_t error = 0;

     S390PCIBusDevice *pbdev;

@@ -742,6 +773,21 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t r2, uintptr_t ra)

             break;

         }

+        /*

+         * If this is an unmap of a PTE, let's try to coalesce multiple unmaps

+         * into as few notifier events as possible.

+         */

+        if (entry.perm == IOMMU_NONE && entry.len == TARGET_PAGE_SIZE) {

+            if (coalesce == 0) {

+                iova = entry.iova;

+            }

+            coalesce += entry.len;

+        } else if (coalesce > 0) {

+            /* Unleash the coalesced unmap before processing a new map */

+            s390_pci_batch_unmap(iommu, iova, coalesce);

+            coalesce = 0;

+        }

+

         start += entry.len;

         while (entry.iova < start && entry.iova < end) {

             if (dma_avail > 0 || entry.perm == IOMMU_NONE) {

@@ -759,6 +805,11 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t r2, uintptr_t ra)

             }

         }

     }

+    if (coalesce) {

+            /* Unleash the coalesced unmap before finishing rpcit */

+            s390_pci_batch_unmap(iommu, iova, coalesce);

+            coalesce = 0;

+    }

     if (again && dma_avail > 0)

         goto retry;

 err:

-- 

2.31.1