hv_hvcrash_ctxt_save() in arch/x86/hyperv/hv_crash.c currently saves segment registers via a general-purpose register (%eax). Update the code to save segment registers (cs, ss, ds, es, fs, gs) directly to the crash context memory using movw. This avoids unnecessary use of a general-purpose register, making the code simpler and more efficient.
The size of the corresponding object file improves as follows: text data bss dec hex filename 4167 176 200 4543 11bf hv_crash-old.o 4151 176 200 4527 11af hv_crash-new.o No functional change occurs to the saved context contents; this is purely a code-quality improvement. Signed-off-by: Uros Bizjak <[email protected]> Cc: "K. Y. Srinivasan" <[email protected]> Cc: Haiyang Zhang <[email protected]> Cc: Wei Liu <[email protected]> Cc: Dexuan Cui <[email protected]> Cc: Long Li <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: "H. Peter Anvin" <[email protected]> --- arch/x86/hyperv/hv_crash.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/hyperv/hv_crash.c b/arch/x86/hyperv/hv_crash.c index fdb277bf73d8..2c7ea7e70854 100644 --- a/arch/x86/hyperv/hv_crash.c +++ b/arch/x86/hyperv/hv_crash.c @@ -207,12 +207,12 @@ static void hv_hvcrash_ctxt_save(void) asm volatile("movq %%cr2, %0" : "=a"(ctxt->cr2)); asm volatile("movq %%cr8, %0" : "=a"(ctxt->cr8)); - asm volatile("movl %%cs, %%eax" : "=a"(ctxt->cs)); - asm volatile("movl %%ss, %%eax" : "=a"(ctxt->ss)); - asm volatile("movl %%ds, %%eax" : "=a"(ctxt->ds)); - asm volatile("movl %%es, %%eax" : "=a"(ctxt->es)); - asm volatile("movl %%fs, %%eax" : "=a"(ctxt->fs)); - asm volatile("movl %%gs, %%eax" : "=a"(ctxt->gs)); + asm volatile("movw %%cs, %0" : "=m"(ctxt->cs)); + asm volatile("movw %%ss, %0" : "=m"(ctxt->ss)); + asm volatile("movw %%ds, %0" : "=m"(ctxt->ds)); + asm volatile("movw %%es, %0" : "=m"(ctxt->es)); + asm volatile("movw %%fs, %0" : "=m"(ctxt->fs)); + asm volatile("movw %%gs, %0" : "=m"(ctxt->gs)); native_store_gdt(&ctxt->gdtr); store_idt(&ctxt->idtr); -- 2.53.0
