[PATCH v3 05/14] x86/svm: Add FEP helpers for SVM tests

Yosry Ahmed
2025-11-10T23:27:10Z

Add helpers to check if FEP is enabled to use as supported() callbacks
in SVM tests for the emulator. Also add a macro that executes an
assembly instruction conditionally with FEP, which will make writing
SVM tests that run with and without FEP more convenient.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
---
lib/x86/desc.h | 8 ++++++++
x86/svm.c | 5 +++++
x86/svm.h | 1 +
3 files changed, 14 insertions(+)

diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index 68f38f3d75333..06c8be65221dc 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -284,6 +284,14 @@ extern unsigned long get_gdt_entry_limit(gdt_entry_t *entry);
#define asm_fep_safe(insn, inputs...) \
__asm_safe_out1(KVM_FEP, insn,, inputs)

+#define asm_conditional_fep_safe(fep, insn, inputs...) \
+({ \
+ if (fep) \
+ asm_fep_safe(insn, inputs); \
+ else \
+ asm_safe(insn, inputs); \
+})
+
#define __asm_safe_out1(fep, insn, output, inputs...) \
({ \
asm volatile(__ASM_TRY(fep, "1f") \
diff --git a/x86/svm.c b/x86/svm.c
index e715e270bc5b7..035367a1e90cf 100644
--- a/x86/svm.c
+++ b/x86/svm.c
@@ -53,6 +53,11 @@ bool default_supported(void)
return true;
}

+bool fep_supported(void)
+{
+ return is_fep_available;
+}
+
bool vgif_supported(void)
{
return this_cpu_has(X86_FEATURE_VGIF);
diff --git a/x86/svm.h b/x86/svm.h
index c1dd84afb25eb..264583a6547ef 100644
--- a/x86/svm.h
+++ b/x86/svm.h
@@ -417,6 +417,7 @@ u64 *npt_get_pdpe(u64 address);
u64 *npt_get_pml4e(void);
bool smp_supported(void);
bool default_supported(void);
+bool fep_supported(void);
bool vgif_supported(void);
bool lbrv_supported(void);
bool tsc_scale_supported(void);
--
2.51.2.1041.gc1ab5b90ca-goog