[PATCH v5 06/15] xen/x86: Add support for the PMAP

[Alejandro Vallejo <alejandro.vallejo@cloud.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>
Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
---
v4->v5:
  * No changes.

v3->v4:
  * Select PMAP KConfig option iff ONDEMAND_DIRECTMAP is used

v2->v3:
  * No changes.

v1->v2:
  * Declare PMAP entries earlier in fixed_addresses
  * Reword the commit message

    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.
---
 xen/arch/x86/include/asm/fixmap.h |  6 ++++++
 xen/arch/x86/include/asm/pmap.h   | 35 +++++++++++++++++++++++++++++++
 xen/common/Kconfig                |  1 +
 3 files changed, 42 insertions(+)
 create mode 100644 xen/arch/x86/include/asm/pmap.h

diff --git a/xen/arch/x86/include/asm/fixmap.h b/xen/arch/x86/include/asm/fixmap.h
index 516ec3fa6c95..80b7b74fd816 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 +55,10 @@ enum fixed_addresses {
     FIX_PV_CONSOLE,
     FIX_XEN_SHARED_INFO,
 #endif /* CONFIG_XEN_GUEST */
+#ifdef CONFIG_HAS_PMAP
+    FIX_PMAP_BEGIN,
+    FIX_PMAP_END = FIX_PMAP_BEGIN + NUM_FIX_PMAP,
+#endif
     /* 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 000000000000..1b3b729b90b2
--- /dev/null
+++ b/xen/arch/x86/include/asm/pmap.h
@@ -0,0 +1,35 @@
+#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)];
+
+    BUILD_BUG_ON(FIX_APIC_BASE - 1 > L1_PAGETABLE_ENTRIES - 1);
+    ASSERT(!(l1e_get_flags(*pl1e) & _PAGE_PRESENT));
+
+    l1e_write(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(pl1e, l1e_empty());
+    flush_tlb_one_local(linear);
+}
+
+#endif /* __ASM_PMAP_H__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 1ee498a3e9a7..5b22b09a4fbc 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -220,6 +220,7 @@ config SPECULATIVE_HARDEN_LOCK
 config ONDEMAND_DIRECTMAP
 	bool "On-Demand Directmap"
 	depends on HAS_ONDEMAND_DIRECTMAP
+	select HAS_PMAP
 	help
 	  Contemporary processors may use speculative execution as a
 	  performance optimisation, but this can potentially be abused by an
-- 
2.47.1