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KVM: SEV-ES: Eliminate #DB intercept when DebugSwap enabled

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Disable #DB for SEV-ES guests when DebugSwap is enabled. There is no point
in such intercept as KVM does not allow guest debug for SEV-ES guests.

Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Link: https://lore.kernel.org/r/20230615063757.3039121-8-aik@amd.com
[sean: add comment as to why KVM disables #DB intercept iff DebugSwap=1]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Alexey Kardashevskiy 2023-06-15 16:37:55 +10:00 committed by Sean Christopherson
parent d1f85fbe83
commit 90cbf6d914
1 changed files with 11 additions and 0 deletions
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11
arch/x86/kvm/svm/sev.c
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@ -2997,6 +2997,17 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
vmcb_set_intercept(&vmcb->control, INTERCEPT_DR7_READ);
vmcb_set_intercept(&vmcb->control, INTERCEPT_DR7_WRITE);
recalc_intercepts(svm);
} else {
/*
* Disable #DB intercept iff DebugSwap is enabled. KVM doesn't
* allow debugging SEV-ES guests, and enables DebugSwap iff
* NO_NESTED_DATA_BP is supported, so there's no reason to
* intercept #DB when DebugSwap is enabled. For simplicity
* with respect to guest debug, intercept #DB for other VMs
* even if NO_NESTED_DATA_BP is supported, i.e. even if the
* guest can't DoS the CPU with infinite #DB vectoring.
*/
clr_exception_intercept(svm, DB_VECTOR);
}
/* Can't intercept XSETBV, HV can't modify XCR0 directly */