[PATCH 5.10.y 4/5] efi: xen: Set EFI_PARAVIRT for Xen dom0 boot on all architectures

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

[ Commit d85e3e34940788578eeffd94e8b7e1d28e7278e9 upstream ]

Currently, the EFI_PARAVIRT flag is only used by Xen dom0 boot on x86,
even though other architectures also support pseudo-EFI boot, where the
core kernel is invoked directly and provided with a set of data tables
that resemble the ones constructed by the EFI stub, which never actually
runs in that case.

Let's fix this inconsistency, and always set this flag when booting dom0
via the EFI boot path. Note that Xen on x86 does not provide the EFI
memory map in this case, whereas other architectures do, so move the
associated EFI_PARAVIRT check into the x86 platform code.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/platform/efi/efi.c      | 8 +++++---
 arch/x86/platform/efi/memmap.c   | 3 +++
 drivers/firmware/efi/fdtparams.c | 4 ++++
 drivers/firmware/efi/memmap.c    | 3 ---
 4 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 8a26e705cb06..41229bcbe0d9 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -234,9 +234,11 @@ int __init efi_memblock_x86_reserve_range(void)
 	data.desc_size		= e->efi_memdesc_size;
 	data.desc_version	= e->efi_memdesc_version;
 
-	rv = efi_memmap_init_early(&data);
-	if (rv)
-		return rv;
+	if (!efi_enabled(EFI_PARAVIRT)) {
+		rv = efi_memmap_init_early(&data);
+		if (rv)
+			return rv;
+	}
 
 	if (add_efi_memmap || do_efi_soft_reserve())
 		do_add_efi_memmap();
diff --git a/arch/x86/platform/efi/memmap.c b/arch/x86/platform/efi/memmap.c
index 620af26b55c0..241464b6dd03 100644
--- a/arch/x86/platform/efi/memmap.c
+++ b/arch/x86/platform/efi/memmap.c
@@ -94,6 +94,9 @@ int __init efi_memmap_install(struct efi_memory_map_data *data)
 {
 	efi_memmap_unmap();
 
+	if (efi_enabled(EFI_PARAVIRT))
+		return 0;
+
 	return __efi_memmap_init(data);
 }
 
diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
index e901f8564ca0..0ec83ba58097 100644
--- a/drivers/firmware/efi/fdtparams.c
+++ b/drivers/firmware/efi/fdtparams.c
@@ -30,11 +30,13 @@ static __initconst const char name[][22] = {
 
 static __initconst const struct {
 	const char	path[17];
+	u8		paravirt;
 	const char	params[PARAMCOUNT][26];
 } dt_params[] = {
 	{
 #ifdef CONFIG_XEN    //  <-------17------>
 		.path = "/hypervisor/uefi",
+		.paravirt = 1,
 		.params = {
 			[SYSTAB] = "xen,uefi-system-table",
 			[MMBASE] = "xen,uefi-mmap-start",
@@ -121,6 +123,8 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
 			pr_err("Can't find property '%s' in DT!\n", pname);
 			return 0;
 		}
+		if (dt_params[i].paravirt)
+			set_bit(EFI_PARAVIRT, &efi.flags);
 		return systab;
 	}
 notfound:
diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
index e6256c48284e..a1180461a445 100644
--- a/drivers/firmware/efi/memmap.c
+++ b/drivers/firmware/efi/memmap.c
@@ -39,9 +39,6 @@ int __init __efi_memmap_init(struct efi_memory_map_data *data)
 	struct efi_memory_map map;
 	phys_addr_t phys_map;
 
-	if (efi_enabled(EFI_PARAVIRT))
-		return 0;
-
 	phys_map = data->phys_map;
 
 	if (data->flags & EFI_MEMMAP_LATE)
-- 
2.45.2.803.g4e1b14247a-goog