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Re: [PATCH v11 0/7] Support x2APIC mode with TCG accelerator


From: Bui Quang Minh
Subject: Re: [PATCH v11 0/7] Support x2APIC mode with TCG accelerator
Date: Wed, 27 Dec 2023 18:03:46 +0700
User-agent: Mozilla Thunderbird

On 12/26/23 16:21, Michael S. Tsirkin wrote:
On Mon, Dec 25, 2023 at 11:40:54PM +0700, Bui Quang Minh wrote:
Hi everyone,

This series implements x2APIC mode in userspace local APIC and the
RDMSR/WRMSR helper to access x2APIC registers in x2APIC mode. Intel iommu
and AMD iommu are adjusted to support x2APIC interrupt remapping. With this
series, we can now boot Linux kernel into x2APIC mode with TCG accelerator
using either Intel or AMD iommu.

Testing to boot my own built Linux 6.3.0-rc2, the kernel successfully boot
with enabled x2APIC and can enumerate CPU with APIC ID 257

Using Intel IOMMU

qemu/build/qemu-system-x86_64 \
   -smp 2,maxcpus=260 \
   -cpu qemu64,x2apic=on \
   -machine q35 \
   -device intel-iommu,intremap=on,eim=on \
   -device qemu64-x86_64-cpu,x2apic=on,core-id=257,socket-id=0,thread-id=0 \
   -m 2G \
   -kernel $KERNEL_DIR \
   -append "nokaslr console=ttyS0 root=/dev/sda earlyprintk=serial 
net.ifnames=0" \
   -drive file=$IMAGE_DIR,format=raw \
   -nographic \
   -s

Using AMD IOMMU

qemu/build/qemu-system-x86_64 \
   -smp 2,maxcpus=260 \
   -cpu qemu64,x2apic=on \
   -machine q35 \
   -device amd-iommu,intremap=on,xtsup=on \
   -device qemu64-x86_64-cpu,x2apic=on,core-id=257,socket-id=0,thread-id=0 \
   -m 2G \
   -kernel $KERNEL_DIR \
   -append "nokaslr console=ttyS0 root=/dev/sda earlyprintk=serial 
net.ifnames=0" \
   -drive file=$IMAGE_DIR,format=raw \
   -nographic \
   -s

Testing the emulated userspace APIC with kvm-unit-tests, disable test
device with this patch

Seems to break build for windows/amd64
https://gitlab.com/mstredhat/qemu/-/pipelines/1118886361/failures

The failure is because when CONFIG_AMD_IOMMU=n, amd_iommu.c is not built so the linker cannot find the definition of amdvi_extended_feature_register (amdvi_extended_feature_register is used in acpi-build.c). I create a stub to solve this problem and it passes all CI tests. I will squash the following changes into patch 6. What do you think about this?

diff --git a/hw/i386/amd_iommu_stub.c b/hw/i386/amd_iommu_stub.c
new file mode 100644
index 0000000000..d62a3732e6
--- /dev/null
+++ b/hw/i386/amd_iommu_stub.c
@@ -0,0 +1,26 @@
+/*
+ * Stubs for AMD IOMMU emulation
+ *
+ * Copyright (C) 2023 Bui Quang Minh <minhquangbui99@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "amd_iommu.h"
+
+uint64_t amdvi_extended_feature_register(AMDVIState *s)
+{
+    return AMDVI_DEFAULT_EXT_FEATURES;
+}
diff --git a/hw/i386/meson.build b/hw/i386/meson.build
index 369c6bf823..d38637b046 100644
--- a/hw/i386/meson.build
+++ b/hw/i386/meson.build
@@ -9,7 +9,8 @@ i386_ss.add(files(

 i386_ss.add(when: 'CONFIG_X86_IOMMU', if_true: files('x86-iommu.c'),
                                       if_false: files('x86-iommu-stub.c'))
-i386_ss.add(when: 'CONFIG_AMD_IOMMU', if_true: files('amd_iommu.c'))
+i386_ss.add(when: 'CONFIG_AMD_IOMMU', if_true: files('amd_iommu.c'),
+                                      if_false: files('amd_iommu_stub.c'))
 i386_ss.add(when: 'CONFIG_I440FX', if_true: files('pc_piix.c'))
i386_ss.add(when: 'CONFIG_MICROVM', if_true: files('microvm.c', 'acpi-microvm.c', 'microvm-dt.c'))
 i386_ss.add(when: 'CONFIG_Q35', if_true: files('pc_q35.c'))


Thanks,
Quang Minh.



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