[Xen-devel] [PATCH 2/2] x86/page: Introduce and use PAGE_HYPERVISOR_UC

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Always map the PCI MMCFG region as strongly uncacheable.  Nothing good will
happen if stray MTRR settings end up converting UC- to WC.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/x86_64/mmconfig_64.c | 2 +-
 xen/include/asm-x86/page.h        | 1 +
 xen/include/asm-x86/x86_64/page.h | 3 +++
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/x86_64/mmconfig_64.c 
b/xen/arch/x86/x86_64/mmconfig_64.c
index a7d2e33..958b6cf 100644
--- a/xen/arch/x86/x86_64/mmconfig_64.c
+++ b/xen/arch/x86/x86_64/mmconfig_64.c
@@ -140,7 +140,7 @@ int pci_mmcfg_arch_enable(unsigned int idx)
 
     if (pci_mmcfg_virt[idx].virt)
         return 0;
-    pci_mmcfg_virt[idx].virt = mcfg_ioremap(cfg, idx, PAGE_HYPERVISOR_UCMINUS);
+    pci_mmcfg_virt[idx].virt = mcfg_ioremap(cfg, idx, PAGE_HYPERVISOR_UC);
     if (!pci_mmcfg_virt[idx].virt) {
         printk(KERN_ERR "PCI: Cannot map MCFG aperture for segment %04x\n",
                cfg->pci_segment);
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index 0b68c5e..263ca5b 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -323,6 +323,7 @@ void efi_update_l4_pgtable(unsigned int l4idx, 
l4_pgentry_t);
 #define __PAGE_HYPERVISOR         (__PAGE_HYPERVISOR_RX | \
                                    _PAGE_DIRTY | _PAGE_RW)
 #define __PAGE_HYPERVISOR_UCMINUS (__PAGE_HYPERVISOR | _PAGE_PCD)
+#define __PAGE_HYPERVISOR_UC      (__PAGE_HYPERVISOR | _PAGE_PCD | _PAGE_PWT)
 
 #define MAP_SMALL_PAGES _PAGE_AVAIL0 /* don't use superpages mappings */
 
diff --git a/xen/include/asm-x86/x86_64/page.h 
b/xen/include/asm-x86/x86_64/page.h
index e102624..603ecac 100644
--- a/xen/include/asm-x86/x86_64/page.h
+++ b/xen/include/asm-x86/x86_64/page.h
@@ -167,10 +167,13 @@ typedef l4_pgentry_t root_pgentry_t;
 /* Dependency on NX being available can't be expressed. */
 # define PAGE_HYPERVISOR         PAGE_HYPERVISOR_RWX
 # define PAGE_HYPERVISOR_UCMINUS (__PAGE_HYPERVISOR_UCMINUS | _PAGE_GLOBAL)
+# define PAGE_HYPERVISOR_UC      (__PAGE_HYPERVISOR_UC      | _PAGE_GLOBAL)
 #else
 # define PAGE_HYPERVISOR         PAGE_HYPERVISOR_RW
 # define PAGE_HYPERVISOR_UCMINUS (__PAGE_HYPERVISOR_UCMINUS | \
                                   _PAGE_GLOBAL | _PAGE_NX)
+# define PAGE_HYPERVISOR_UC      (__PAGE_HYPERVISOR_UC | \
+                                  _PAGE_GLOBAL | _PAGE_NX)
 #endif
 
 #endif /* __X86_64_PAGE_H__ */
-- 
2.1.4


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