qemu-kvm/kvm-s390x-pci-coalesce-unmap-operations.patch

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2023-04-04 12:34:43 +00:00
From b972c5a2763a91024725c147cf1691ed8e180c7c 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 09/11] s390x/pci: coalesce unmap operations
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Cédric Le Goater <clg@redhat.com>
RH-MergeRequest: 250: s390x/pci: reset ISM passthrough devices on shutdown and system reset
RH-Bugzilla: 2163713
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: [2/4] 7b5ee38eca565f5a7cbede4b9883ba3a508fb46c
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:
--
2.37.3