From: Peng Hao <peng.hao2@zte.com.cn>
To: pbonzini@redhat.com, rkrcmar@redhat.com, stefanha@gmail.com
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Peng Hao <peng.hao2@zte.com.cn>
Subject: [PATCH V5 3/3] kvm/x86 : add document for coalesced pio
Date: Sun, 14 Oct 2018 07:09:57 +0800 [thread overview]
Message-ID: <1539472197-111085-4-git-send-email-peng.hao2@zte.com.cn> (raw)
In-Reply-To: <1539472197-111085-1-git-send-email-peng.hao2@zte.com.cn>
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
---
Documentation/virtual/kvm/api.txt | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 9615b9e..d3a0497 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3678,18 +3678,19 @@ the definition of struct kvm_nested_state, see KVM_GET_NESTED_STATE.
4.116 KVM_(UN)REGISTER_COALESCED_MMIO
-Capability: KVM_CAP_COALESCED_MMIO
+Capability: KVM_CAP_COALESCED_MMIO (for coalesced mmio)
+ KVM_CAP_COALESCED_PIO (for coalesced pio)
Architectures: all
Type: vm ioctl
Parameters: struct kvm_coalesced_mmio_zone
Returns: 0 on success, < 0 on error
-Coalesced mmio is a performance optimization that defers hardware
+Coalesced I/O is a performance optimization that defers hardware
register write emulation so that userspace exits are avoided. It is
typically used to reduce the overhead of emulating frequently accessed
hardware registers.
-When a hardware register is configured for coalesced mmio, write accesses
+When a hardware register is configured for coalesced I/O, write accesses
do not exit to userspace and their value is recorded in a shared coalesced
ring in the kernel.
@@ -3700,6 +3701,9 @@ will cause the shared coalesced ring to be processed by userspace
before emulating the current access. That will reduce the first write
access to userspace.
+Coalesced pio is based on coalesced mmio. There is little difference between
+coalesced mmio and pio except that coalesced pio is used for ioport.
+
5. The kvm_run structure
------------------------
--
1.8.3.1
next prev parent reply other threads:[~2018-10-13 14:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 23:09 [PATCH V5 0/3] introduce coalesced pio support Peng Hao
2018-10-13 23:09 ` [PATCH V5 1/3] kvm/x86 : add " Peng Hao
2018-10-13 23:09 ` [PATCH V5 2/3] kvm/x86 : add document for coalesced mmio Peng Hao
2018-10-13 23:09 ` Peng Hao [this message]
2018-10-15 17:22 ` [PATCH V5 0/3] introduce coalesced pio support Paolo Bonzini
2018-10-17 10:08 ` Stefan Hajnoczi
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