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authorNikos Nikoleris <nikos.nikoleris@arm.com>2017-02-27 15:57:31 +0000
committerAndreas Sandberg <andreas.sandberg@arm.com>2017-04-03 16:39:00 +0000
commit4b164f8382e78e26dc796559ee58ee31abca5d4c (patch)
treeb88e294f121a6399d378afe941432769dc09cf97
parent31199bba53493bcfb4d130d8c739d698d21b5dd5 (diff)
downloadgem5-4b164f8382e78e26dc796559ee58ee31abca5d4c.tar.xz
arm: Treat Write-Through Normal memory as Non-Cacheable
A completed write to a memory location that is Write-Through Cacheable has to be visible to an external observer without the need of explicit cache maintenance. This change adds support for Write-Through Cacheable Normal memory and treats it as Non-cacheable. This incurs a small penalty as accesses to the memory do not fill in the cache but does not violate the properties of the memory type. Change-Id: Iee17ef9d952a550be9ad660b1e60e9f6c4ef2c2d Reviewed-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com> Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-on: https://gem5-review.googlesource.com/2280 Maintainer: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
-rw-r--r--src/arch/arm/table_walker.cc29
1 files changed, 24 insertions, 5 deletions
diff --git a/src/arch/arm/table_walker.cc b/src/arch/arm/table_walker.cc
index 82462ab33..8783d0a00 100644
--- a/src/arch/arm/table_walker.cc
+++ b/src/arch/arm/table_walker.cc
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2010, 2012-2016 ARM Limited
+ * Copyright (c) 2010, 2012-2017 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
@@ -1342,7 +1342,10 @@ TableWalker::memAttrsAArch64(ThreadContext *tc, TlbEntry &te,
attr_hi == 2 ? 2 : 1;
te.innerAttrs = attr_lo == 1 ? 0 :
attr_lo == 2 ? 6 : 5;
- te.nonCacheable = (attr_hi == 1) || (attr_lo == 1);
+ // Treat write-through memory as uncacheable, this is safe
+ // but for performance reasons not optimal.
+ te.nonCacheable = (attr_hi == 1) || (attr_hi == 2) ||
+ (attr_lo == 1) || (attr_lo == 2);
}
} else {
uint8_t attrIndx = lDescriptor.attrIndx();
@@ -1377,9 +1380,25 @@ TableWalker::memAttrsAArch64(ThreadContext *tc, TlbEntry &te,
// Cacheability
te.nonCacheable = false;
- if (te.mtype == TlbEntry::MemoryType::Device || // Device memory
- attr_hi == 0x8 || // Normal memory, Outer Non-cacheable
- attr_lo == 0x8) { // Normal memory, Inner Non-cacheable
+ if (te.mtype == TlbEntry::MemoryType::Device) { // Device memory
+ te.nonCacheable = true;
+ }
+ // Treat write-through memory as uncacheable, this is safe
+ // but for performance reasons not optimal.
+ switch (attr_hi) {
+ case 0x1 ... 0x3: // Normal Memory, Outer Write-through transient
+ case 0x4: // Normal memory, Outer Non-cacheable
+ case 0x8 ... 0xb: // Normal Memory, Outer Write-through non-transient
+ te.nonCacheable = true;
+ }
+ switch (attr_lo) {
+ case 0x1 ... 0x3: // Normal Memory, Inner Write-through transient
+ case 0x9 ... 0xb: // Normal Memory, Inner Write-through non-transient
+ warn_if(!attr_hi, "Unpredictable behavior");
+ case 0x4: // Device-nGnRE memory or
+ // Normal memory, Inner Non-cacheable
+ case 0x8: // Device-nGRE memory or
+ // Normal memory, Inner Write-through non-transient
te.nonCacheable = true;
}