From f859e4a3b9088a76fe733fd0312b0922f90b85e1 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Wed, 16 Aug 2017 13:01:03 +0100 Subject: [PATCH] x86/mm: Reduce debug overhead of __virt_to_maddr() __virt_to_maddr() is used very frequently, but has a large footprint due to its assertions and comparasons. Rearange its logic to drop one assertion entirely, encoding its check in a second assertion (with no additional branch, and the comparason performed with a 32bit immediate rather than requiring a movabs). Bloat-o-meter net report is: add/remove: 0/0 grow/shrink: 1/72 up/down: 3/-2169 (-2166) along with a reduction of 32 assertion frames (895 down to 861) Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- xen/include/asm-x86/x86_64/page.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/xen/include/asm-x86/x86_64/page.h b/xen/include/asm-x86/x86_64/page.h index 947e52bd14..a9ba6f0a56 100644 --- a/xen/include/asm-x86/x86_64/page.h +++ b/xen/include/asm-x86/x86_64/page.h @@ -51,13 +51,16 @@ extern unsigned long xen_virt_end; static inline unsigned long __virt_to_maddr(unsigned long va) { - ASSERT(va >= XEN_VIRT_START); ASSERT(va < DIRECTMAP_VIRT_END); if ( va >= DIRECTMAP_VIRT_START ) va -= DIRECTMAP_VIRT_START; else { - ASSERT(va < XEN_VIRT_END); + BUILD_BUG_ON(XEN_VIRT_END - XEN_VIRT_START != GB(1)); + /* Signed, so ((long)XEN_VIRT_START >> 30) fits in an imm32. */ + ASSERT(((long)va >> (PAGE_ORDER_1G + PAGE_SHIFT)) == + ((long)XEN_VIRT_START >> (PAGE_ORDER_1G + PAGE_SHIFT))); + va += xen_phys_start - XEN_VIRT_START; } return (va & ma_va_bottom_mask) | -- 2.30.2