From: Jim Mattson jmattson@google.com
[ Upstream commit cfb634fe3052aefc4e1360fa322018c9a0b49755 ]
According to volume 3 of the SDM, bits 63:15 and 12:4 of the exit qualification field for debug exceptions are reserved (cleared to 0). However, the SDM is incorrect about bit 16 (corresponding to DR6.RTM). This bit should be set if a debug exception (#DB) or a breakpoint exception (#BP) occurred inside an RTM region while advanced debugging of RTM transactional regions was enabled. Note that this is the opposite of DR6.RTM, which "indicates (when clear) that a debug exception (#DB) or breakpoint exception (#BP) occurred inside an RTM region while advanced debugging of RTM transactional regions was enabled."
There is still an issue with stale DR6 bits potentially being misreported for the current debug exception. DR6 should not have been modified before vectoring the #DB exception, and the "new DR6 bits" should be available somewhere, but it was and they aren't.
Fixes: b96fb439774e1 ("KVM: nVMX: fixes to nested virt interrupt injection") Signed-off-by: Jim Mattson jmattson@google.com Reviewed-by: Sean Christopherson sean.j.christopherson@intel.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/vmx.c | 7 +++++-- 2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 0722b7745382..ccc23203b327 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -176,6 +176,7 @@ enum {
#define DR6_BD (1 << 13) #define DR6_BS (1 << 14) +#define DR6_BT (1 << 15) #define DR6_RTM (1 << 16) #define DR6_FIXED_1 0xfffe0ff0 #define DR6_INIT 0xffff0ff0 diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 32721ef9652d..1dcd7f13ce76 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3159,10 +3159,13 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit } } else { if (vmcs12->exception_bitmap & (1u << nr)) { - if (nr == DB_VECTOR) + if (nr == DB_VECTOR) { *exit_qual = vcpu->arch.dr6; - else + *exit_qual &= ~(DR6_FIXED_1 | DR6_BT); + *exit_qual ^= DR6_RTM; + } else { *exit_qual = 0; + } return 1; } }