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Subject[PATCH -v2] target-i386: Reenable RDTSCP support on Opteron_G[345] CPU models CPU models
On Wed, Dec 12, 2018 at 05:52:35PM -0200, Eduardo Habkost wrote:
> Why did you remove this entry from PC_COMPAT_2_4?
>
> We must keep compatibility with old behavior of Opteron_G2 on
> pc-2.4, even if the old behavior was incorrect.

Ok, hunk reverted. v2 below.

Thx.

---
From: Borislav Petkov <bp@suse.de>

The missing functionality was added ~3 years ago with the Linux commit

46896c73c1a4 ("KVM: svm: add support for RDTSCP")

so reenable RDTSCP support on those CPU models.

Opteron_G2 - being family 15, model 6, doesn't have RDTSCP support
(the real hardware doesn't have it. K8 got RDTSCP support with the NPT
models, i.e., models >= 0x40).

Document the host's minimum required kernel version, while at it.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
v2: Keep Opteron_G2 in PC_COMPAT_2_4 unchanged.

include/hw/i386/pc.h | 13 +++++++++++++
qemu-doc.texi | 13 +++++++++++++
target/i386/cpu.c | 11 ++++-------
3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 9d29c4b1df2a..236d962d2547 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -296,6 +296,19 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);

#define PC_COMPAT_3_1 \
HW_COMPAT_3_1 \
+ {\
+ .driver = "Opteron_G3" "-" TYPE_X86_CPU,\
+ .property = "rdtscp",\
+ .value = "off",\
+ },{\
+ .driver = "Opteron_G4" "-" TYPE_X86_CPU,\
+ .property = "rdtscp",\
+ .value = "off",\
+ },{\
+ .driver = "Opteron_G5" "-" TYPE_X86_CPU,\
+ .property = "rdtscp",\
+ .value = "off",\
+ },

#define PC_COMPAT_3_0 \
HW_COMPAT_3_0 \
diff --git a/qemu-doc.texi b/qemu-doc.texi
index f7ad1dfe4b69..16b955cbf985 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -37,6 +37,7 @@
* QEMU System emulator for non PC targets::
* QEMU Guest Agent::
* QEMU User space emulator::
+* System requirements::
* Implementation notes::
* Deprecated features::
* Supported build platforms::
@@ -2813,6 +2814,18 @@ Act as if the host page size was 'pagesize' bytes
Run the emulation in single step mode.
@end table

+@node System requirements
+@chapter System requirements
+
+@section KVM kernel module
+
+On x86_64 hosts, the default set of CPU features enabled by the KVM accelerator
+require the host to be running Linux v4.5 or newer.
+
+The OpteronG[345] CPU models require KVM support for RDTSCP, which was
+added with Linux 4.5 which is supported by the major distros. And even
+if RHEL7 has kernel 3.10, KVM there has the required functionality there
+to make it close to a 4.5 or newer kernel.

@include qemu-tech.texi

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index f81d35e1f914..a7def11b27cd 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -2706,7 +2706,6 @@ static X86CPUDefinition builtin_x86_defs[] = {
CPUID_DE | CPUID_FP87,
.features[FEAT_1_ECX] =
CPUID_EXT_CX16 | CPUID_EXT_SSE3,
- /* Missing: CPUID_EXT2_RDTSCP */
.features[FEAT_8000_0001_EDX] =
CPUID_EXT2_LM | CPUID_EXT2_NX | CPUID_EXT2_SYSCALL,
.features[FEAT_8000_0001_ECX] =
@@ -2730,9 +2729,9 @@ static X86CPUDefinition builtin_x86_defs[] = {
.features[FEAT_1_ECX] =
CPUID_EXT_POPCNT | CPUID_EXT_CX16 | CPUID_EXT_MONITOR |
CPUID_EXT_SSE3,
- /* Missing: CPUID_EXT2_RDTSCP */
.features[FEAT_8000_0001_EDX] =
- CPUID_EXT2_LM | CPUID_EXT2_NX | CPUID_EXT2_SYSCALL,
+ CPUID_EXT2_LM | CPUID_EXT2_NX | CPUID_EXT2_SYSCALL |
+ CPUID_EXT2_RDTSCP,
.features[FEAT_8000_0001_ECX] =
CPUID_EXT3_MISALIGNSSE | CPUID_EXT3_SSE4A |
CPUID_EXT3_ABM | CPUID_EXT3_SVM | CPUID_EXT3_LAHF_LM,
@@ -2757,10 +2756,9 @@ static X86CPUDefinition builtin_x86_defs[] = {
CPUID_EXT_POPCNT | CPUID_EXT_SSE42 | CPUID_EXT_SSE41 |
CPUID_EXT_CX16 | CPUID_EXT_SSSE3 | CPUID_EXT_PCLMULQDQ |
CPUID_EXT_SSE3,
- /* Missing: CPUID_EXT2_RDTSCP */
.features[FEAT_8000_0001_EDX] =
CPUID_EXT2_LM | CPUID_EXT2_PDPE1GB | CPUID_EXT2_NX |
- CPUID_EXT2_SYSCALL,
+ CPUID_EXT2_SYSCALL | CPUID_EXT2_RDTSCP,
.features[FEAT_8000_0001_ECX] =
CPUID_EXT3_FMA4 | CPUID_EXT3_XOP |
CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_MISALIGNSSE |
@@ -2788,10 +2786,9 @@ static X86CPUDefinition builtin_x86_defs[] = {
CPUID_EXT_AES | CPUID_EXT_POPCNT | CPUID_EXT_SSE42 |
CPUID_EXT_SSE41 | CPUID_EXT_CX16 | CPUID_EXT_FMA |
CPUID_EXT_SSSE3 | CPUID_EXT_PCLMULQDQ | CPUID_EXT_SSE3,
- /* Missing: CPUID_EXT2_RDTSCP */
.features[FEAT_8000_0001_EDX] =
CPUID_EXT2_LM | CPUID_EXT2_PDPE1GB | CPUID_EXT2_NX |
- CPUID_EXT2_SYSCALL,
+ CPUID_EXT2_SYSCALL | CPUID_EXT2_RDTSCP,
.features[FEAT_8000_0001_ECX] =
CPUID_EXT3_TBM | CPUID_EXT3_FMA4 | CPUID_EXT3_XOP |
CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_MISALIGNSSE |
--
2.19.1
--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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