[PATCH] SVM: reliably detect if SVM was disabled by BIOS

Joerg Roedel
2007-06-21T17:51:22Z

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From: Joerg Roedel <joerg.roedel-5C7GfCeVMHo@public.gmane.org>

This patch adds an implementation to the svm is_disabled function to
detect reliably if the BIOS disabled the SVM feature in the CPU. This
fixes the issues with kernel panics when loading the kvm-amd module on
machines where SVM is available but disabled.

Signed-off-by: Joerg Roedel <joerg.roedel-5C7GfCeVMHo@public.gmane.org>

--
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diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index fa17d6d..54aa83a 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -1727,6 +1727,12 @@ static void svm_inject_page_fault(struct kvm_vcpu *vcpu,

static int is_disabled(void)
{
+ uint64_t vm_cr;
+
+ rdmsrl(MSR_VM_CR, vm_cr);
+ if (vm_cr & (1 << SVM_VM_CR_SVM_DISABLE))
+ return 1;
+
return 0;
}

diff --git a/drivers/kvm/svm.h b/drivers/kvm/svm.h
index 5e93814..005a9c5 100644
--- a/drivers/kvm/svm.h
+++ b/drivers/kvm/svm.h
@@ -175,8 +175,11 @@ struct __attribute__ ((__packed__)) vmcb {
#define SVM_CPUID_FUNC 0x8000000a

#define MSR_EFER_SVME_MASK (1ULL << 12)
+#define MSR_VM_CR 0xc0010114ULL
#define MSR_VM_HSAVE_PA 0xc0010117ULL

+#define SVM_VM_CR_SVM_DISABLE 4
+
#define SVM_SELECTOR_S_SHIFT 4
#define SVM_SELECTOR_DPL_SHIFT 5
#define SVM_SELECTOR_P_SHIFT 7

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