[PATCH v2] xen/x86: Add support for the PMAP

[Elias El Yandouzi <eliasely@amazon.com>]

From: Julien Grall <jgrall@amazon.com>

PMAP will be used in a follow-up patch to bootstrap map domain
page infrastructure -- we need some way to map pages to setup the
mapcache without a direct map.

The functions pmap_{map, unmap} open code {set, clear}_fixmap to break
the loop.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Signed-off-by: Elias El Yandouzi <eliasely@amazon.com>

----

    The PMAP infrastructure was upstream separately for Arm since
    Hongyan sent the secret-free hypervisor series. So this is a new
    patch to plumb the feature on x86.

    Changes in v2:
        * Declare PMAP entries earlier in fixed_addresses
        * Reword the commit message

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 350f41b832..16b2a32469 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -25,6 +25,7 @@ config X86
 	select HAS_PASSTHROUGH
 	select HAS_PCI
 	select HAS_PCI_MSI
+	select HAS_PMAP
 	select HAS_SCHED_GRANULARITY
 	select HAS_UBSAN
 	select HAS_VPCI if HVM
diff --git a/xen/arch/x86/include/asm/fixmap.h b/xen/arch/x86/include/asm/fixmap.h
index 516ec3fa6c..a7ac365fc6 100644
--- a/xen/arch/x86/include/asm/fixmap.h
+++ b/xen/arch/x86/include/asm/fixmap.h
@@ -21,6 +21,8 @@
 
 #include <xen/acpi.h>
 #include <xen/pfn.h>
+#include <xen/pmap.h>
+
 #include <asm/apicdef.h>
 #include <asm/msi.h>
 #include <acpi/apei.h>
@@ -53,6 +55,8 @@ enum fixed_addresses {
     FIX_PV_CONSOLE,
     FIX_XEN_SHARED_INFO,
 #endif /* CONFIG_XEN_GUEST */
+    FIX_PMAP_BEGIN,
+    FIX_PMAP_END = FIX_PMAP_BEGIN + NUM_FIX_PMAP,
     /* Everything else should go further down. */
     FIX_APIC_BASE,
     FIX_IO_APIC_BASE_0,
diff --git a/xen/arch/x86/include/asm/pmap.h b/xen/arch/x86/include/asm/pmap.h
new file mode 100644
index 0000000000..62746e191d
--- /dev/null
+++ b/xen/arch/x86/include/asm/pmap.h
@@ -0,0 +1,25 @@
+#ifndef __ASM_PMAP_H__
+#define __ASM_PMAP_H__
+
+#include <asm/fixmap.h>
+
+static inline void arch_pmap_map(unsigned int slot, mfn_t mfn)
+{
+    unsigned long linear = (unsigned long)fix_to_virt(slot);
+    l1_pgentry_t *pl1e = &l1_fixmap[l1_table_offset(linear)];
+
+    ASSERT(!(l1e_get_flags(*pl1e) & _PAGE_PRESENT));
+
+    l1e_write_atomic(pl1e, l1e_from_mfn(mfn, PAGE_HYPERVISOR));
+}
+
+static inline void arch_pmap_unmap(unsigned int slot)
+{
+    unsigned long linear = (unsigned long)fix_to_virt(slot);
+    l1_pgentry_t *pl1e = &l1_fixmap[l1_table_offset(linear)];
+
+    l1e_write_atomic(pl1e, l1e_empty());
+    flush_tlb_one_local(linear);
+}
+
+#endif /* __ASM_PMAP_H__ */
-- 
2.40.1