Merge tag 'hyperv-fixes-signed-20231121' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

Pull hyperv fixes from Wei Liu:

 - One fix for the KVP daemon (Ani Sinha)

 - Fix for the detection of E820_TYPE_PRAM in a Gen2 VM (Saurabh Sengar)

 - Micro-optimization for hv_nmi_unknown() (Uros Bizjak)

* tag 'hyperv-fixes-signed-20231121' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux:
  x86/hyperv: Use atomic_try_cmpxchg() to micro-optimize hv_nmi_unknown()
  x86/hyperv: Fix the detection of E820_TYPE_PRAM in a Gen2 VM
  hv/hv_kvp_daemon: Some small fixes for handling NM keyfiles

2 files changed, 25 insertions, 5 deletions

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 21556ad87f4b..8f3a4d16bb79 100644
--- 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;
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index e6bba12c759c..01fa06dd06b6 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -262,11 +262,14 @@ static uint32_t  __init ms_hyperv_platform(void)
 static int hv_nmi_unknown(unsigned int val, struct pt_regs *regs)
 {
 	static atomic_t nmi_cpu = ATOMIC_INIT(-1);
+	unsigned int old_cpu, this_cpu;
 
 	if (!unknown_nmi_panic)
 		return NMI_DONE;
 
-	if (atomic_cmpxchg(&nmi_cpu, -1, raw_smp_processor_id()) != -1)
+	old_cpu = -1;
+	this_cpu = raw_smp_processor_id();
+	if (!atomic_try_cmpxchg(&nmi_cpu, &old_cpu, this_cpu))
 		return NMI_HANDLED;
 
 	return NMI_DONE;