52929cc849
- kvm-target-i386-Fix-conditional-CONFIG_SYNDBG-enablement.patch [RHEL-7130] - kvm-target-i386-Exclude-hv-syndbg-from-hv-passthrough.patch [RHEL-7130] - Resolves: RHEL-7130 ([Hyper-V][RHEL9.2] Nested Hyper-V on KVM: L1 Windows VM with BIOS mode fails to boot up when using '-cpu host,hv_passthrough’ flag)
103 lines
4.5 KiB
Diff
103 lines
4.5 KiB
Diff
From 0288537593cd4452a2523b686b297dad3735f7f8 Mon Sep 17 00:00:00 2001
|
|
From: Vitaly Kuznetsov <vkuznets@redhat.com>
|
|
Date: Thu, 17 Apr 2025 15:30:50 +0200
|
|
Subject: [PATCH 2/2] target/i386: Exclude 'hv-syndbg' from 'hv-passthrough'
|
|
|
|
RH-Author: Vitaly Kuznetsov <vkuznets@redhat.com>
|
|
RH-MergeRequest: 352: hyper-v: exclude 'hv-syndbg' from 'hv-passthrough' set
|
|
RH-Jira: RHEL-7130
|
|
RH-Acked-by: Maxim Levitsky <None>
|
|
RH-Acked-by: Ani Sinha <anisinha@redhat.com>
|
|
RH-Acked-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
|
|
RH-Commit: [2/2] bf276ad5b340139f71b92e656a0c7756a55dec0b (vkuznets/qemu-kvm)
|
|
|
|
Windows with Hyper-V role enabled doesn't boot with 'hv-passthrough' when
|
|
no debugger is configured, this significantly limits the usefulness of the
|
|
feature as there's no support for subtracting Hyper-V features from CPU
|
|
flags at this moment (e.g. "-cpu host,hv-passthrough,-hv-syndbg" does not
|
|
work). While this is also theoretically fixable, 'hv-syndbg' is likely
|
|
very special and unneeded in the default set. Genuine Hyper-V doesn't seem
|
|
to enable it either.
|
|
|
|
Introduce 'skip_passthrough' flag to 'kvm_hyperv_properties' and use it as
|
|
one-off to skip 'hv-syndbg' when enabling features in 'hv-passthrough'
|
|
mode. Note, "-cpu host,hv-passthrough,hv-syndbg" can still be used if
|
|
needed.
|
|
|
|
As both 'hv-passthrough' and 'hv-syndbg' are debug features, the change
|
|
should not have any effect on production environments.
|
|
|
|
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
|
|
Link: https://lore.kernel.org/r/20240917160051.2637594-3-vkuznets@redhat.com
|
|
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
(cherry picked from commit 7d7b9c7655a26e09c800ef40373078a80e90d9f3)
|
|
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
|
|
---
|
|
docs/system/i386/hyperv.rst | 13 +++++++++----
|
|
target/i386/kvm/kvm.c | 7 +++++--
|
|
2 files changed, 14 insertions(+), 6 deletions(-)
|
|
|
|
diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst
|
|
index 2505dc4c86..009947e391 100644
|
|
--- a/docs/system/i386/hyperv.rst
|
|
+++ b/docs/system/i386/hyperv.rst
|
|
@@ -262,14 +262,19 @@ Supplementary features
|
|
``hv-passthrough``
|
|
In some cases (e.g. during development) it may make sense to use QEMU in
|
|
'pass-through' mode and give Windows guests all enlightenments currently
|
|
- supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU
|
|
- flag.
|
|
+ supported by KVM.
|
|
|
|
Note: ``hv-passthrough`` flag only enables enlightenments which are known to QEMU
|
|
(have corresponding 'hv-' flag) and copies ``hv-spinlocks`` and ``hv-vendor-id``
|
|
values from KVM to QEMU. ``hv-passthrough`` overrides all other 'hv-' settings on
|
|
- the command line. Also, enabling this flag effectively prevents migration as the
|
|
- list of enabled enlightenments may differ between target and destination hosts.
|
|
+ the command line.
|
|
+
|
|
+ Note: ``hv-passthrough`` does not enable ``hv-syndbg`` which can prevent certain
|
|
+ Windows guests from booting when used without proper configuration. If needed,
|
|
+ ``hv-syndbg`` can be enabled additionally.
|
|
+
|
|
+ Note: ``hv-passthrough`` effectively prevents migration as the list of enabled
|
|
+ enlightenments may differ between target and destination hosts.
|
|
|
|
``hv-enforce-cpuid``
|
|
By default, KVM allows the guest to use all currently supported Hyper-V
|
|
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
|
|
index 5bf77d761f..94b678e9e3 100644
|
|
--- a/target/i386/kvm/kvm.c
|
|
+++ b/target/i386/kvm/kvm.c
|
|
@@ -913,6 +913,7 @@ static struct {
|
|
uint32_t bits;
|
|
} flags[2];
|
|
uint64_t dependencies;
|
|
+ bool skip_passthrough;
|
|
} kvm_hyperv_properties[] = {
|
|
[HYPERV_FEAT_RELAXED] = {
|
|
.desc = "relaxed timing (hv-relaxed)",
|
|
@@ -1041,7 +1042,8 @@ static struct {
|
|
{.func = HV_CPUID_FEATURES, .reg = R_EDX,
|
|
.bits = HV_FEATURE_DEBUG_MSRS_AVAILABLE}
|
|
},
|
|
- .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED)
|
|
+ .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED),
|
|
+ .skip_passthrough = true,
|
|
},
|
|
[HYPERV_FEAT_MSR_BITMAP] = {
|
|
.desc = "enlightened MSR-Bitmap (hv-emsr-bitmap)",
|
|
@@ -1450,7 +1452,8 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
|
|
* hv_build_cpuid_leaf() uses this info to build guest CPUIDs.
|
|
*/
|
|
for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) {
|
|
- if (hyperv_feature_supported(cs, feat)) {
|
|
+ if (hyperv_feature_supported(cs, feat) &&
|
|
+ !kvm_hyperv_properties[feat].skip_passthrough) {
|
|
cpu->hyperv_features |= BIT(feat);
|
|
}
|
|
}
|
|
--
|
|
2.48.1
|
|
|