From 7d7b9c7655a26e09c800ef40373078a80e90d9f3 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Tue, 17 Sep 2024 18:00:49 +0200 Subject: target/i386: Exclude 'hv-syndbg' from 'hv-passthrough' 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 Link: https://lore.kernel.org/r/20240917160051.2637594-3-vkuznets@redhat.com Signed-off-by: Paolo Bonzini --- target/i386/kvm/kvm.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'target/i386') diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 1ec4977a8e..fd9f198892 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -934,6 +934,7 @@ static struct { uint32_t bits; } flags[2]; uint64_t dependencies; + bool skip_passthrough; } kvm_hyperv_properties[] = { [HYPERV_FEAT_RELAXED] = { .desc = "relaxed timing (hv-relaxed)", @@ -1062,7 +1063,8 @@ 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)", @@ -1471,7 +1473,8 @@ 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); } } -- cgit v1.2.3