linux

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Sean Christopherson 0caa0a77c2 KVM: SVM: Probe and load MSR_TSC_AUX regardless of RDTSCP support in host

Probe MSR_TSC_AUX whether or not RDTSCP is supported in the host, and
if probing succeeds, load the guest's MSR_TSC_AUX into hardware prior to
VMRUN.  Because SVM doesn't support interception of RDPID, RDPID cannot
be disallowed in the guest (without resorting to binary translation).
Leaving the host's MSR_TSC_AUX in hardware would leak the host's value to
the guest if RDTSCP is not supported.

Note, there is also a kernel bug that prevents leaking the host's value.
The host kernel initializes MSR_TSC_AUX if and only if RDTSCP is
supported, even though the vDSO usage consumes MSR_TSC_AUX via RDPID.
I.e. if RDTSCP is not supported, there is no host value to leak.  But,
if/when the host kernel bug is fixed, KVM would start leaking MSR_TSC_AUX
in the case where hardware supports RDPID but RDTSCP is unavailable for
whatever reason.

Probing MSR_TSC_AUX will also allow consolidating the probe and define
logic in common x86, and will make it simpler to condition the existence
of MSR_TSX_AUX (from the guest's perspective) on RDTSCP *or* RDPID.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2021-05-07 06:06:17 -04:00

boot

- turn the stack canary into a normal __percpu variable on 32-bit which

2021-04-27 17:45:09 -07:00

configs

module: remove EXPORT_UNUSED_SYMBOL*

2021-02-08 12:28:07 +01:00

crypto

Objtool updates in this cycle were:

2021-04-28 12:53:24 -07:00

entry

Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com>