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KVM: arm64: Allow setting of ID_AA64PFR0_EL1.CSV2 from userspace
We now expose ID_AA64PFR0_EL1.CSV2=1 to guests running on hosts that are immune to Spectre-v2, but that don't have this field set, most likely because they predate the specification. However, this prevents the migration of guests that have started on a host the doesn't fake this CSV2 setting to one that does, as KVM rejects the write to ID_AA64PFR0_EL2 on the grounds that it isn't what is already there. In order to fix this, allow userspace to set this field as long as this doesn't result in a promising more than what is already there (setting CSV2 to 0 is acceptable, but setting it to 1 when it is already set to 0 isn't). Fixes: e102623 ("KVM: arm64: Set CSV2 for guests on hardware unaffected by Spectre-v2") Reported-by: Peng Liang <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Acked-by: Will Deacon <[email protected]> Link: https://lore.kernel.org/r/[email protected]
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Marc Zyngier
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Nov 12, 2020
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