From 7e7c5dab29ed99bda0fb5d810db6f12ae4aa2608 Mon Sep 17 00:00:00 2001

From: "plai@redhat.com" <plai@redhat.com>

Date: Tue, 26 Nov 2019 18:36:54 +0000

Subject: [PATCH 10/11] x86/cpu: Add support for UMONITOR/UMWAIT/TPAUSE

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x86/cpu: Add support for UMONITOR/UMWAIT/TPAUSE

RH-Author: plai@redhat.com

Message-id: <1574797015-32564-7-git-send-email-plai@redhat.com>

Patchwork-id: 92695

O-Subject: [RHEL8.2 qemu-kvm PATCH 6/7] x86/cpu: Add support for UMONITOR/UMWAIT/TPAUSE

Bugzilla: 1634827

RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>

RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

RH-Acked-by: Igor Mammedov <imammedo@redhat.com>

From: Tao Xu <tao3.xu@intel.com>

UMONITOR, UMWAIT and TPAUSE are a set of user wait instructions.

This patch adds support for user wait instructions in KVM. Availability

of the user wait instructions is indicated by the presence of the CPUID

feature flag WAITPKG CPUID.0x07.0x0:ECX[5]. User wait instructions may

be executed at any privilege level, and use IA32_UMWAIT_CONTROL MSR to

set the maximum time.

The patch enable the umonitor, umwait and tpause features in KVM.

Because umwait and tpause can put a (psysical) CPU into a power saving

state, by default we dont't expose it to kvm and enable it only when

guest CPUID has it. And use QEMU command-line "-overcommit cpu-pm=on"

(enable_cpu_pm is enabled), a VM can use UMONITOR, UMWAIT and TPAUSE

instructions. If the instruction causes a delay, the amount of time

delayed is called here the physical delay. The physical delay is first

computed by determining the virtual delay (the time to delay relative to

the VM’s timestamp counter). Otherwise, UMONITOR, UMWAIT and TPAUSE cause

an invalid-opcode exception(#UD).

The release document ref below link:

https://software.intel.com/sites/default/files/\

managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf

Co-developed-by: Jingqi Liu <jingqi.liu@intel.com>

Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>

Signed-off-by: Tao Xu <tao3.xu@intel.com>

Message-Id: <20191011074103.30393-2-tao3.xu@intel.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit 67192a298f5bf98f96e5516c3b6474c49e4853cd)

Signed-off-by: Paul Lai <plai@redhat.com>

Resolved Conflicts:

	target/i386/cpu.c

	target/i386/cpu.h

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 target/i386/cpu.c | 2 +-

 target/i386/cpu.h | 2 ++

 target/i386/kvm.c | 6 ++++++

 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c

index 87b0502..7d2afc7 100644

--- a/target/i386/cpu.c

+++ b/target/i386/cpu.c

@@ -1016,7 +1016,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {

         .type = CPUID_FEATURE_WORD,

         .feat_names = {

             NULL, "avx512vbmi", "umip", "pku",

-            "ospke", NULL, "avx512vbmi2", NULL,

+            "ospke", "waitpkg", "avx512vbmi2", NULL,

             "gfni", "vaes", "vpclmulqdq", "avx512vnni",

             "avx512bitalg", NULL, "avx512-vpopcntdq", NULL,

             "la57", NULL, NULL, NULL,

diff --git a/target/i386/cpu.h b/target/i386/cpu.h

index 7ab8ee9..fac98aa 100644

--- a/target/i386/cpu.h

+++ b/target/i386/cpu.h

@@ -708,6 +708,8 @@ typedef uint64_t FeatureWordArray[FEATURE_WORDS];

 #define CPUID_7_0_ECX_UMIP     (1U << 2)

 #define CPUID_7_0_ECX_PKU      (1U << 3)

 #define CPUID_7_0_ECX_OSPKE    (1U << 4)

+/* UMONITOR/UMWAIT/TPAUSE Instructions */

+#define CPUID_7_0_ECX_WAITPKG  (1U << 5)

 #define CPUID_7_0_ECX_VBMI2    (1U << 6) /* Additional VBMI Instrs */

 #define CPUID_7_0_ECX_GFNI     (1U << 8)

 #define CPUID_7_0_ECX_VAES     (1U << 9)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c

index ffd01f0..0fd5650 100644

--- a/target/i386/kvm.c

+++ b/target/i386/kvm.c

@@ -392,6 +392,12 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,

         if (host_tsx_blacklisted()) {

             ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE);

         }

+    } else if (function == 7 && index == 0 && reg == R_ECX) {

+        if (enable_cpu_pm) {

+            ret |= CPUID_7_0_ECX_WAITPKG;

+        } else {

+            ret &= ~CPUID_7_0_ECX_WAITPKG;

+        }

     } else if (function == 7 && index == 0 && reg == R_EDX) {

         /*

          * Linux v4.17-v4.20 incorrectly return ARCH_CAPABILITIES on SVM hosts.

-- 

1.8.3.1