On Mon, Apr 08, 2024 at 12:44:54AM +1200, Kai Huang wrote:
TL;DR:
The commit message is waaay too verbose for no good reason. You don't
really need to repeat all the history around this code.
---
arch/x86/kernel/process.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index b8441147eb5e..5ba8a9c1e47a 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -813,18 +813,16 @@ void __noreturn stop_this_cpu(void *dummy)
mcheck_cpu_clear(c);
/*
- * Use wbinvd on processors that support SME. This provides support
- * for performing a successful kexec when going from SME inactive
- * to SME active (or vice-versa). The cache must be cleared so that
- * if there are entries with the same physical address, both with and
- * without the encryption bit, they don't race each other when flushed
- * and potentially end up with the wrong entry being committed to
- * memory.
+ * The kernel could leave caches in incoherent state on SME/TDX
+ * capable platforms. Flush cache to avoid silent memory
+ * corruption for these platforms.
*
- * Test the CPUID bit directly because the machine might've cleared
- * X86_FEATURE_SME due to cmdline options.
+ * stop_this_cpu() is not a fast path, just do unconditional
+ * WBINVD for simplicity. But only do WBINVD for bare-metal
+ * as TDX guests and SEV-ES/SEV-SNP guests will get unexpected
+ * (and unnecessary) #VE and may unable to handle.
s/#VE/exception/
On SEV it is #VC, not #VE.