[V2,01/12] x86/virt/tdx: Make tdh_vp_enter() noinstr

Commit Message

Adrian Hunter Jan. 29, 2025, 9:58 a.m. UTC

Make tdh_vp_enter() noinstr because KVM requires VM entry to be noinstr
for 2 reasons:
 1. The use of context tracking via guest_state_enter_irqoff() and
    guest_state_exit_irqoff()
 2. The need to avoid IRET between VM-exit and NMI handling in order to
    avoid prematurely releasing NMI inhibit.

Consequently make __seamcall_saved_ret() noinstr also. Currently
tdh_vp_enter() is the only caller of __seamcall_saved_ret().

Signed-off-by: Adrian Hunter <[e-mail]>
---
TD vcpu enter/exit v2:
 - New patch
---
 arch/x86/virt/vmx/tdx/seamcall.S | 3 +++
 arch/x86/virt/vmx/tdx/tdx.c      | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

Patch

diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
index 5b1f2286aea9..6854c52c374b 100644
--- a/arch/x86/virt/vmx/tdx/seamcall.S
+++ b/arch/x86/virt/vmx/tdx/seamcall.S
@@ -41,6 +41,9 @@  SYM_FUNC_START(__seamcall_ret)
 	TDX_MODULE_CALL host=1 ret=1
 SYM_FUNC_END(__seamcall_ret)
 
+/* KVM requires non-instrumentable __seamcall_saved_ret() for TDH.VP.ENTER */
+.section .noinstr.text, "ax"
+
 /*
  * __seamcall_saved_ret() - Host-side interface functions to SEAM software
  * (the P-SEAMLDR or the TDX module), with saving output registers to the
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 4a010e65276d..1515c467dd86 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1511,7 +1511,7 @@  static void tdx_clflush_page(struct page *page)
 	clflush_cache_range(page_to_virt(page), PAGE_SIZE);
 }
 
-u64 tdh_vp_enter(struct tdx_vp *td, struct tdx_module_args *args)
+noinstr u64 tdh_vp_enter(struct tdx_vp *td, struct tdx_module_args *args)
 {
 	args->rcx = tdx_tdvpr_pa(td);