x86/CPU/AMD: Add RDSEED fix for Zen5

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There's an issue with RDSEED's 16-bit and 32-bit register output
variants on Zen5 which return a random value of 0 "at a rate inconsistent
with randomness while incorrectly signaling success (CF=1)". Search the
web for AMD-SB-7055 for more detail.

Add a fix glue which checks microcode revisions.

  [ bp: Add microcode revisions checking, rewrite. ]

Cc: stable@vger.kernel.org
Signed-off-by: Gregory Price <gourry@gourry.net>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20251018024010.4112396-1-gourry@gourry.net

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Gregory Price 2025-10-20 11:13:55 +02:00 • committed by Borislav Petkov (AMD)

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commit 607b9fb2ce

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