Commit 7e8037b0 authored by Saurabh Sengar's avatar Saurabh Sengar Committed by Wei Liu
Browse files

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



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: default avatarSaurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Message-ID: <1699691867-9827-1-git-send-email-ssengar@linux.microsoft.com>
parent c3803203

arch/x86/hyperv/hv_init.c

+21 −4
Original line number Diff line number Diff line
@@ -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;