CVE-2026-72239

In the Linux kernel, the following vulnerability has been resolved:

x86/virt/sev: Revert "Drop WBINVD before setting MSRAMD64SYSCFGSNPEN"

Revert

  99cf1fb58e68 ("x86/virt/sev: Drop WBINVD before setting MSRAMD64SYSCFGSNPEN").

Section 8.8 of the SNP spec says:

  Before invoking SNPINITEX with INIT_RMP set to 1, software must ensure

  that no CPUs contain dirty cache lines for the memory containing the RMP.

Cachelines can be moved from cache to cache in a dirty state. The

wbinvdonallcpus() before SNPINIT_EX flushes the caches for each CPU, but

if the IPIs for WBINVD race with this dirty cacheline movement, it is possible

that they may not get flushed, violating the firmware requirement.

Doing wbinvdonall_cpus() before setting SNPEn is safer since the RMP

table is not yet in use.

  [ Heroically bisected by Srikanth. ]

  [ bp: Massage commit message. ]