[SRU][oracular:linux-azure][PATCH 1/1 v2 Revert "UBUNTU: SAUCE: x86/hyperv: temporarily disable CET SS on SEV-SNP due to a paravisor bug"

[John Cabaj]

BugLink: https://bugs.launchpad.net/bugs/2079841

This reverts commit 29fa1211e69aa9a21be5517e795b99156a4df78e.

Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 21 ---------------------
 1 file changed, 21 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index c9dee20fa8a9..82a356fbde4e 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -581,27 +581,6 @@ static void __init ms_hyperv_init_platform(void)
 	if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
 		mark_tsc_unstable("running on Hyper-V");
 
-	/*
-	 * Mask CET Shadow Stack on SEV-SNP due to a CPUID emulation bug in
-	 * the paravisor on old Azure SEV-SNP hosts, e.g., 10.0.20348.2867-2-0.
-	 * Due to the bug, paranoid_xstate_size_valid() in a v6.6 or newer
-	 * kernel prints a warning "XSAVE consistency problem: size 848 != kernel_size 832"
-	 * and the kernel disables XSAVE completely; the early 'init' program or
-	 * any later program may get core-dumped due to "invalid opcode", if
-	 * they assume XSAVE is available (e.g., it looks like
-	 * libgnutls.so.30.27.0 tries to unconditionally use XSAVE.
-	 *
-	 * Note: the SNP paravisor bug only affects a v6.6+ Linux kernel
-	 * (CET Shadow Stack is firstly enabled in v6.6) when the VM is a "v5"
-	 * SNP VM on Azure. A "v6" SNP VM is not affected, and a TDX VM is also
-	 * not affectd since the versions of paravisor for them are already
-	 * fixed. The fix for the "v5" VMs would roll out around September or
-	 * October, 2024.
-	 */
-       if (ms_hyperv.paravisor_present &&
-	   hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
-                setup_clear_cpu_cap(X86_FEATURE_SHSTK);
-
 	hardlockup_detector_disable();
 }
 
-- 
2.43.0