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Linux 6.15 Adds AMD Zen 5 SRSO Mitigation For KVM, Preps For Attack Vector Controls
While there is a lot of exciting new x86_64 CPU features coming with Linux 6.15, there is also some of the not so fun changes too: namely the 'x86/bugs' pull request to bring the latest CPU security mitigation work to the mainline kernel.
This new Zen 5 specific SRSO mitigation is for the Kernel-based Virtual Machine (KVM) and labeled as SRSO_MSR_FIX. Switch back to enabling the bit when virtualization is enabled and to clear the bit when virtualization is disabled because using a MSR slot would clear the bit when the guest is exited and any training the guest has done, would potentially influence the host kernel when execution enters the kernel and hasn't VMRUN the guest yet." This doesn't change things outside the context of virtual machine (VM) use with Zen 5 processors.
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