x86/hyperv: Fix the detection of E820_TYPE_PRAM in a Gen2 VM

[ Upstream commit 7e8037b099c0bbe8f2109dc452dbcab8d400fc53 ]

A Gen2 VM doesn't support legacy PCI/PCIe, so both raw_pci_ops and
raw_pci_ext_ops are NULL, and pci_subsys_init() -> pcibios_init()
doesn't call pcibios_resource_survey() -> e820__reserve_resources_late();
as a result, any emulated persistent memory of E820_TYPE_PRAM (12) via
the kernel parameter memmap=nn[KMG]!ss is not added into iomem_resource
and hence can't be detected by register_e820_pmem().

Fix this by directly calling e820__reserve_resources_late() in
hv_pci_init(), which is called from arch_initcall(pci_arch_init).

It's ok to move a Gen2 VM's e820__reserve_resources_late() from
subsys_initcall(pci_subsys_init) to arch_initcall(pci_arch_init) because
the code in-between doesn't depend on the E820 resources.
e820__reserve_resources_late() depends on e820__reserve_resources(),
which has been called earlier from setup_arch().

For a Gen-2 VM, the new hv_pci_init() also adds any memory of
E820_TYPE_PMEM (7) into iomem_resource, and acpi_nfit_register_region() ->
acpi_nfit_insert_resource() -> region_intersects() returns
REGION_INTERSECTS, so the memory of E820_TYPE_PMEM won't get added twice.

Changed the local variable "int gen2vm" to "bool gen2vm".

Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1699691867-9827-1-git-send-email-ssengar@linux.microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 21556ad..8f3a4d1 100644 (file)
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -15,6 +15,7 @@
 #include <linux/io.h>
 #include <asm/apic.h>
 #include <asm/desc.h>
+#include <asm/e820/api.h>
 #include <asm/sev.h>
 #include <asm/ibt.h>
 #include <asm/hypervisor.h>
@@ -286,15 +287,31 @@ static int hv_cpu_die(unsigned int cpu)
 
 static int __init hv_pci_init(void)
 {
-       int gen2vm = efi_enabled(EFI_BOOT);
+       bool gen2vm = efi_enabled(EFI_BOOT);
 
        /*
-        * For Generation-2 VM, we exit from pci_arch_init() by returning 0.
-        * The purpose is to suppress the harmless warning:
+        * A Generation-2 VM doesn't support legacy PCI/PCIe, so both
+        * raw_pci_ops and raw_pci_ext_ops are NULL, and pci_subsys_init() ->
+        * pcibios_init() doesn't call pcibios_resource_survey() ->
+        * e820__reserve_resources_late(); as a result, any emulated persistent
+        * memory of E820_TYPE_PRAM (12) via the kernel parameter
+        * memmap=nn[KMG]!ss is not added into iomem_resource and hence can't be
+        * detected by register_e820_pmem(). Fix this by directly calling
+        * e820__reserve_resources_late() here: e820__reserve_resources_late()
+        * depends on e820__reserve_resources(), which has been called earlier
+        * from setup_arch(). Note: e820__reserve_resources_late() also adds
+        * any memory of E820_TYPE_PMEM (7) into iomem_resource, and
+        * acpi_nfit_register_region() -> acpi_nfit_insert_resource() ->
+        * region_intersects() returns REGION_INTERSECTS, so the memory of
+        * E820_TYPE_PMEM won't get added twice.
+        *
+        * We return 0 here so that pci_arch_init() won't print the warning:
         * "PCI: Fatal: No config space access function found"
         */
-       if (gen2vm)
+       if (gen2vm) {
+               e820__reserve_resources_late();
                return 0;
+       }
 
        /* For Generation-1 VM, we'll proceed in pci_arch_init().  */
        return 1;