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05 April 2024, 19:05:47 UTC
Revision 1eaafe91a0df4157521b6417b3dd8430bf5f52f0 authored by Jim Mattson on 09 May 2018, 21:29:35 UTC, committed by Radim Krčmář on 24 May 2018, 16:38:34 UTC 
kvm: x86: IA32_ARCH_CAPABILITIES is always supported
 
If there is a possibility that a VM may migrate to a Skylake host,
then the hypervisor should report IA32_ARCH_CAPABILITIES.RSBA[bit 2]
as being set (future work, of course). This implies that
CPUID.(EAX=7,ECX=0):EDX.ARCH_CAPABILITIES[bit 29] should be
set. Therefore, kvm should report this CPUID bit as being supported
whether or not the host supports it.  Userspace is still free to clear
the bit if it chooses.

For more information on RSBA, see Intel's white paper, "Retpoline: A
Branch Target Injection Mitigation" (Document Number 337131-001),
currently available at https://bugzilla.kernel.org/show_bug.cgi?id=199511.

Since the IA32_ARCH_CAPABILITIES MSR is emulated in kvm, there is no
dependency on hardware support for this feature.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Fixes: 28c1c9fabf48 ("KVM/VMX: Emulate MSR_IA32_ARCH_CAPABILITIES")
Cc: stable@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
1 parent c4d2188
History
Tip revision: 1eaafe91a0df4157521b6417b3dd8430bf5f52f0 authored by Jim Mattson on 09 May 2018, 21:29:35 UTC
kvm: x86: IA32_ARCH_CAPABILITIES is always supported
Tip revision: 1eaafe9
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