[PATCH 1/3] acpi/processor: fix evaluating _PDC method when running as Xen dom0

[Roger Pau Monne <roger.pau@citrix.com>]

When running as a Xen dom0 the number of CPUs available to Linux can
be different from the number of CPUs present on the system, but in
order to properly fetch processor performance related data _PDC must
be executed on all the physical CPUs online on the system.

The current checks in processor_physically_present() result in some
processor objects not getting their _PDC methods evaluated when Linux
is running as Xen dom0.  Fix this by introducing a custom function to
use when running as Xen dom0 in order to check whether a processor
object matches a CPU that's online.

Fixes: 5d554a7bb064 ('ACPI: processor: add internal processor_physically_present()')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
 arch/x86/include/asm/xen/hypervisor.h | 10 ++++++++++
 arch/x86/xen/enlighten.c              | 27 +++++++++++++++++++++++++++
 drivers/acpi/processor_pdc.c          | 11 +++++++++++
 3 files changed, 48 insertions(+)

diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 16f548a661cf..b9f512138043 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -61,4 +61,14 @@ void __init xen_pvh_init(struct boot_params *boot_params);
 void __init mem_map_via_hcall(struct boot_params *boot_params_p);
 #endif
 
+#ifdef CONFIG_XEN_DOM0
+bool __init xen_processor_present(uint32_t acpi_id);
+#else
+static inline bool xen_processor_present(uint32_t acpi_id)
+{
+	BUG();
+	return false;
+}
+#endif
+
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b8db2148c07d..d4c44361a26c 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -346,3 +346,30 @@ void xen_arch_unregister_cpu(int num)
 }
 EXPORT_SYMBOL(xen_arch_unregister_cpu);
 #endif
+
+#ifdef CONFIG_XEN_DOM0
+bool __init xen_processor_present(uint32_t acpi_id)
+{
+	unsigned int i, maxid;
+	struct xen_platform_op op = {
+		.cmd = XENPF_get_cpuinfo,
+		.interface_version = XENPF_INTERFACE_VERSION,
+	};
+	int ret = HYPERVISOR_platform_op(&op);
+
+	if (ret)
+		return false;
+
+	maxid = op.u.pcpu_info.max_present;
+	for (i = 0; i <= maxid; i++) {
+		op.u.pcpu_info.xen_cpuid = i;
+		ret = HYPERVISOR_platform_op(&op);
+		if (ret)
+			continue;
+		if (op.u.pcpu_info.acpi_id == acpi_id)
+			return op.u.pcpu_info.flags & XEN_PCPU_FLAGS_ONLINE;
+	}
+
+	return false;
+}
+#endif
diff --git a/drivers/acpi/processor_pdc.c b/drivers/acpi/processor_pdc.c
index 8c3f82c9fff3..18fb04523f93 100644
--- a/drivers/acpi/processor_pdc.c
+++ b/drivers/acpi/processor_pdc.c
@@ -14,6 +14,8 @@
 #include <linux/acpi.h>
 #include <acpi/processor.h>
 
+#include <xen/xen.h>
+
 #include "internal.h"
 
 static bool __init processor_physically_present(acpi_handle handle)
@@ -47,6 +49,15 @@ static bool __init processor_physically_present(acpi_handle handle)
 		return false;
 	}
 
+	if (xen_initial_domain())
+		/*
+		 * When running as a Xen dom0 the number of processors Linux
+		 * sees can be different from the real number of processors on
+		 * the system, and we still need to execute _PDC for all of
+		 * them.
+		 */
+		return xen_processor_present(acpi_id);
+
 	type = (acpi_type == ACPI_TYPE_DEVICE) ? 1 : 0;
 	cpuid = acpi_get_cpuid(handle, type, acpi_id);
 
-- 
2.37.3