x86: introduce ioremap_wc()

In order for a to-be-introduced ERMS form of memcpy() to not regress
boot performance on certain systems when video output is active, we
first need to arrange for avoiding further dependency on firmware
setting up MTRRs in a way we can actually further modify. On many
systems, due to the continuously growing amounts of installed memory,
MTRRs get configured with at least one huge WB range, and with MMIO
ranges below 4Gb then forced to UC via overlapping MTRRs. mtrr_add(), as
it is today, can't deal with such a setup. Hence on such systems we
presently leave the frame buffer mapped UC, leading to significantly
reduced performance when using REP STOSB / REP MOVSB.

On post-PentiumII hardware (i.e. any that's capable of running 64-bit
code), an effective memory type of WC can be achieved without MTRRs, by
simply referencing the respective PAT entry from the PTEs. While this
will leave the switch to ERMS forms of memset() and memcpy() with
largely unchanged performance, the change here on its own improves
performance on affected systems quite significantly: Measuring just the
individual affected memcpy() invocations yielded a speedup by a factor
of over 250 on my initial (Skylake) test system. memset() isn't getting
improved by as much there, but still by a factor of about 20.

While adding {__,}PAGE_HYPERVISOR_WC, also add {__,}PAGE_HYPERVISOR_WT
to, at the very least, make clear what PTE flags this memory type uses.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

diff --git a/xen/arch/x86/include/asm/mm.h b/xen/arch/x86/include/asm/mm.h
index 9b9de4c6bef730801b824e97504557c98a648054..bdde24d2cec34fb0d36f632843fd5a8882f4a2e7 100644 (file)
--- a/xen/arch/x86/include/asm/mm.h
+++ b/xen/arch/x86/include/asm/mm.h
@@ -602,6 +602,8 @@ void destroy_perdomain_mapping(struct domain *, unsigned long va,
                                unsigned int nr);
 void free_perdomain_mappings(struct domain *);
 
+void __iomem *ioremap_wc(paddr_t, size_t);
+
 extern int memory_add(unsigned long spfn, unsigned long epfn, unsigned int pxm);
 
 void domain_set_alloc_bitsize(struct domain *d);

diff --git a/xen/arch/x86/include/asm/page.h b/xen/arch/x86/include/asm/page.h
index 1d080cffbe84b3cb5a905c53d0aaa3c3574776ec..447491cd09d6232f6f72ced94bd8a8c6ca17c211 100644 (file)
--- a/xen/arch/x86/include/asm/page.h
+++ b/xen/arch/x86/include/asm/page.h
@@ -349,8 +349,10 @@ void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t);
 #define __PAGE_HYPERVISOR_RX      (_PAGE_PRESENT | _PAGE_ACCESSED)
 #define __PAGE_HYPERVISOR         (__PAGE_HYPERVISOR_RX | \
                                    _PAGE_DIRTY | _PAGE_RW)
+#define __PAGE_HYPERVISOR_WT      (__PAGE_HYPERVISOR | _PAGE_PWT)
 #define __PAGE_HYPERVISOR_UCMINUS (__PAGE_HYPERVISOR | _PAGE_PCD)
 #define __PAGE_HYPERVISOR_UC      (__PAGE_HYPERVISOR | _PAGE_PCD | _PAGE_PWT)
+#define __PAGE_HYPERVISOR_WC      (__PAGE_HYPERVISOR | _PAGE_PAT)
 #define __PAGE_HYPERVISOR_SHSTK   (__PAGE_HYPERVISOR_RO | _PAGE_DIRTY)
 
 #define MAP_SMALL_PAGES _PAGE_AVAIL0 /* don't use superpages mappings */

diff --git a/xen/arch/x86/include/asm/x86_64/page.h b/xen/arch/x86/include/asm/x86_64/page.h
index cb1db107c424e97d6ded588b13fc351710086198..26bdb4b19bb9210cf8c3bb24eb03482ea11dfaf5 100644 (file)
--- a/xen/arch/x86/include/asm/x86_64/page.h
+++ b/xen/arch/x86/include/asm/x86_64/page.h
@@ -152,6 +152,10 @@ static inline intpte_t put_pte_flags(unsigned int x)
                                  _PAGE_GLOBAL | _PAGE_NX)
 #define PAGE_HYPERVISOR_UC      (__PAGE_HYPERVISOR_UC | \
                                  _PAGE_GLOBAL | _PAGE_NX)
+#define PAGE_HYPERVISOR_WC      (__PAGE_HYPERVISOR_WC | \
+                                 _PAGE_GLOBAL | _PAGE_NX)
+#define PAGE_HYPERVISOR_WT      (__PAGE_HYPERVISOR_WT | \
+                                 _PAGE_GLOBAL | _PAGE_NX)
 
 #endif /* __X86_64_PAGE_H__ */
 

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index b80e4ab9c56416e6ac55a196c0ac2c5755b746d1..9c7c616253f53a1388d9f237dcd534a9474e9b49 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5895,6 +5895,20 @@ void __iomem *ioremap(paddr_t pa, size_t len)
     return (void __force __iomem *)va;
 }
 
+void __iomem *__init ioremap_wc(paddr_t pa, size_t len)
+{
+    mfn_t mfn = _mfn(PFN_DOWN(pa));
+    unsigned int offs = pa & (PAGE_SIZE - 1);
+    unsigned int nr = PFN_UP(offs + len);
+    void *va;
+
+    WARN_ON(page_is_ram_type(mfn_x(mfn), RAM_TYPE_CONVENTIONAL));
+
+    va = __vmap(&mfn, nr, 1, 1, PAGE_HYPERVISOR_WC, VMAP_DEFAULT);
+
+    return (void __force __iomem *)(va + offs);
+}
+
 int create_perdomain_mapping(struct domain *d, unsigned long va,
                              unsigned int nr, l1_pgentry_t **pl1tab,
                              struct page_info **ppg)

diff --git a/xen/drivers/video/vesa.c b/xen/drivers/video/vesa.c
index 2c1bbd927806dcf850fa83175eec2017a37755e9..f9169f701f15e9f37f1c729c0547a370cbd7aa24 100644 (file)
--- a/xen/drivers/video/vesa.c
+++ b/xen/drivers/video/vesa.c
@@ -9,9 +9,9 @@
 #include <xen/param.h>
 #include <xen/xmalloc.h>
 #include <xen/kernel.h>
+#include <xen/mm.h>
 #include <xen/vga.h>
 #include <asm/io.h>
-#include <asm/page.h>
 #include "font.h"
 #include "lfb.h"
 
@@ -103,7 +103,7 @@ void __init vesa_init(void)
     lfbp.text_columns = vlfb_info.width / font->width;
     lfbp.text_rows = vlfb_info.height / font->height;
 
-    lfbp.lfb = lfb = ioremap(lfb_base(), vram_remap);
+    lfbp.lfb = lfb = ioremap_wc(lfb_base(), vram_remap);
     if ( !lfb )
         return;
 
@@ -179,8 +179,7 @@ void __init vesa_mtrr_init(void)
 
 static void lfb_flush(void)
 {
-    if ( vesa_mtrr == 3 )
-        __asm__ __volatile__ ("sfence" : : : "memory");
+    __asm__ __volatile__ ("sfence" : : : "memory");
 }
 
 void __init vesa_endboot(bool_t keep)

diff --git a/xen/drivers/video/vga.c b/xen/drivers/video/vga.c
index b7f04d0d97f466c60af71cdaa3eec563686f9e9a..5e58f83c97ff175512008c102c884c103c5a7faa 100644 (file)
--- a/xen/drivers/video/vga.c
+++ b/xen/drivers/video/vga.c
@@ -79,7 +79,7 @@ void __init video_init(void)
     {
     case XEN_VGATYPE_TEXT_MODE_3:
         if ( page_is_ram_type(paddr_to_pfn(0xB8000), RAM_TYPE_CONVENTIONAL) ||
-             ((video = ioremap(0xB8000, 0x8000)) == NULL) )
+             ((video = ioremap_wc(0xB8000, 0x8000)) == NULL) )
             return;
         outw(0x200a, 0x3d4); /* disable cursor */
         columns = vga_console_info.u.text_mode_3.columns;
@@ -164,7 +164,11 @@ void __init video_endboot(void)
     {
     case XEN_VGATYPE_TEXT_MODE_3:
         if ( !vgacon_keep )
+        {
             memset(video, 0, columns * lines * 2);
+            iounmap(video);
+            video = ZERO_BLOCK_PTR;
+        }
         break;
     case XEN_VGATYPE_VESA_LFB:
     case XEN_VGATYPE_EFI_LFB: