This patch is some preliminary work for assigning a special RID for use
with EFI mappings. It just creates some macros that will switch the RID if
XEN is defined. A subsequent patch makes use of these macros.
The basic idea of this approach is to switch to this RID, which is in the
range reserved for the hypervisor, before making EFI, PAL or SAL calls. The
page fault handler where the identity mapping checks for this RID, if
present it does the identity mapping, else it just follows the normal
mapping rules. In this way, VMX domains should not be able to access this
memory, and they should be able to use the virtual addresses that are used
by EFI for their own purposes.
Cc: Tristan Gingold <tgingold@xxxxxxx>
Cc: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
Index: xen-unstable.hg/xen/include/asm-ia64/linux-xen/linux/efi.h
===================================================================
--- xen-unstable.hg.orig/xen/include/asm-ia64/linux-xen/linux/efi.h
2007-10-29 11:34:42.000000000 +0900
+++ xen-unstable.hg/xen/include/asm-ia64/linux-xen/linux/efi.h 2007-10-29
11:40:55.000000000 +0900
@@ -1,6 +1,8 @@
#ifndef _LINUX_EFI_H
#define _LINUX_EFI_H
+#ifndef __ASSEMBLY__
+
/*
* Extensible Firmware Interface
* Based on 'Extensible Firmware Interface Specification' version 0.9, April
30, 1999
@@ -419,4 +421,94 @@ struct efi_generic_dev_path {
u16 length;
} __attribute ((packed));
+#ifdef XEN
+/*
+ * According to xen/arch/ia64/xen/regionreg.c the RID space is broken
+ * up into chunks, one per domain, and 0th block is for Xen. The 0th block
+ * is broken up into small blocks, which are used for metaphisical mappins,
+ * except for the 0th small block which is used by Xen.
+ *
+ * By default each large block is 18 bits wide, which is also the minimum
+ * width. Each small block is by default 1/64 the width of a large block,
+ * which is also the maximum devision. In other words each small block is
+ * at least 12 bits wide.
+ *
+ * What isn't obvious to me is how the 0th small block is divided up.
+ * While xen/arch/ia64/xen/regionreg.c seems to handle allocating RIDs for
+ * domains, they hypervisor's RIDs seem to be handled in a bit more of an
+ * ad-hoc fashion.
+ *
+ * In xen/include/asm-ia64/mmu_context.h there is IA64_REGION_ID_KERNEL.
+ * This is used to form an RID in the follwing way:
+ *
+ * a: bit 0: VHPT
+ * b: bit 1: reserved (0)
+ * c: bits 2-7: log 2 page_size
+ * d: bits 8-10: Region (0-7, corresponding to the 8 region registers)
+ * e: bits 10-N: IA64_REGION_ID_KERNEL (0)
+ * f: bits N-53: reserved (0)
+ *
+ * N is defined by the platform. Areas c and d above form the RID, it just
+ * happens to be further divided in two due to the way that its value is
+ * calculated buy the code. This subdivision does not reflect any hardware
+ * limitation. The hardware sets the limit of the with of this area to
+ * between 18 and 24 bits.
+ *
+ * As we are only using the first 4 bits (3 bits in area d and 1 bit in
+ * area e) of RID space it easily fits inside the 0th small block, which
+ * is 12 bits wide.
+ *
+ * For EFI we use the following RID
+ *
+ * a: bit 0: VHPT (1)
+ * b: bit 1: reserved (0)
+ * c: bits 2-7: log 2 page_size
+ * d: bits 8-10: Region (0-7, corresponding to the 8 region registers) +
+ * e: bits 10-N: IA64_REGION_ID_KERNEL (1)
+ * f: bits N-53: reserved (0)
+ *
+ * + Only 0 is used as we only need one RID. Its not really important
+ * what this number is, so long as its between 0 and 7.
+ *
+ * The nice thing about this is that we are still only using 4 bits of RID
+ * space, so it shouldn't have any chance of running into an adjacent
+ * small-block.
+ *
+ * It would actually be possible to just use a IA64_REGION_ID_KERNEL
+ * based RID for EFI use. The important thing is that it is in the 0th
+ * small block, and that not available to domains. But as we have
+ * lots of space, its seems to be nice and clean to just use a separate
+ * RID for EFI.
+ *
+ * This can be trivially changed by updating the definition of XEN_EFI_RID.
+ */
+
+#define XEN_EFI_RR_SAVE(rr6, rr7) do { \
+ rr6 = ia64_get_rr(6); \
+ rr7 = ia64_get_rr(7); \
+ ia64_set_rr(6, XEN_EFI_RID); \
+ ia64_set_rr(7, XEN_EFI_RID); \
+ ia64_srlz_d(); \
+} while (0)
+
+#define XEN_EFI_RR_RESTORE(rr6, rr7) do { \
+ ia64_set_rr(6, rr6); \
+ ia64_set_rr(7, rr7); \
+ ia64_srlz_d(); \
+} while (0)
+
+#else
+#define XEN_EFI_RR_SAVE() do {} while (0)
+#define XEN_EFI_RR_RESTORE() do {} while (0)
+#endif /* XEN */
+
+#endif /* !__ASSEMBLY__ */
+
+#ifdef XEN
+#include <asm/mmu_context.h> /* For IA64_REGION_ID_EFI and ia64_rid() */
+#include <asm/pgtable.h> /* IA64_GRANULE_SHIFT */
+#define XEN_EFI_RID ((ia64_rid(XEN_IA64_REGION_ID_EFI, 0) << 8) | \
+ (IA64_GRANULE_SHIFT << 2) | 1)
+#endif /* XEN */
+
#endif /* _LINUX_EFI_H */
Index: xen-unstable.hg/xen/include/asm-ia64/mmu_context.h
===================================================================
--- xen-unstable.hg.orig/xen/include/asm-ia64/mmu_context.h 2007-10-29
11:34:42.000000000 +0900
+++ xen-unstable.hg/xen/include/asm-ia64/mmu_context.h 2007-10-29
11:35:21.000000000 +0900
@@ -3,6 +3,7 @@
//dummy file to resolve non-arch-indep include
#ifdef XEN
#define IA64_REGION_ID_KERNEL 0
+#define XEN_IA64_REGION_ID_EFI 1
#define ia64_rid(ctx,addr) (((ctx) << 3) | (addr >> 61))
#ifndef __ASSEMBLY__
--
--
Horms
H: http://www.vergenet.net/~horms/
W: http://www.valinux.co.jp/en/
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