[PATCH v4] acpi/processor: sanitize _OSC/_PDC capabilities for Xen dom0

[Jason Andryuk <jandryuk@xxxxxxxxx>]

From: Roger Pau Monne <roger.pau@xxxxxxxxxx>

The Processor capability bits notify ACPI of the OS capabilities, and
so ACPI can adjust the return of other Processor methods taking the OS
capabilities into account.

When Linux is running as a Xen dom0, the hypervisor is the entity
in charge of processor power management, and hence Xen needs to make
sure the capabilities reported by _OSC/_PDC match the capabilities of
the driver in Xen.

Introduce a small helper to sanitize the buffer when running as Xen
dom0.

When Xen supports HWP, this serves as the equivalent of commit
a21211672c9a ("ACPI / processor: Request native thermal interrupt
handling via _OSC") to avoid SMM crashes.  Xen will set bit
ACPI_PROC_CAP_COLLAB_PROC_PERF (bit 12) in the capability bits and the
_OSC/_PDC call will apply it.

[ jandryuk: Mention Xen HWP's need.  Support _OSC & _PDC ]
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
---
v4:
Use xen_santize_proc_cap_bits() name - Michal
Rephrase comment - Michal

v3:
Move xen_sanitize_pdc() call to arch_acpi_set_proc_cap_bits() to cover
_OSC and _PDC.
drivers/xen/pcpu.c is CONFIG_DOM0 && CONFIG_X86

v2:
Move local variables in acpi_processor_eval_pdc() to reuse in both conditions.
---
 arch/x86/include/asm/acpi.h           | 14 ++++++++++++++
 arch/x86/include/asm/xen/hypervisor.h |  9 +++++++++
 drivers/xen/pcpu.c                    | 21 +++++++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
index c8a7fc23f63c..f896eed4516c 100644
--- a/arch/x86/include/asm/acpi.h
+++ b/arch/x86/include/asm/acpi.h
@@ -16,6 +16,9 @@
 #include <asm/x86_init.h>
 #include <asm/cpufeature.h>
 #include <asm/irq_vectors.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
 
 #ifdef CONFIG_ACPI_APEI
 # include <asm/pgtable_types.h>
@@ -127,6 +130,17 @@ static inline void arch_acpi_set_proc_cap_bits(u32 *cap)
        if (!cpu_has(c, X86_FEATURE_MWAIT) ||
            boot_option_idle_override == IDLE_NOMWAIT)
                *cap &= ~(ACPI_PROC_CAP_C_C1_FFH | ACPI_PROC_CAP_C_C2C3_FFH);
+
+       if (xen_initial_domain()) {
+               /*
+                * When Linux is running as Xen dom0, the hypervisor is the
+                * entity in charge of the processor power management, and so
+                * Xen needs to check the OS capabilities reported in the
+                * processor capabilities buffer matches what the hypervisor
+                * driver supports.
+                */
+               xen_sanitize_proc_cap_bits(cap);
+       }
 }
 
 static inline bool acpi_has_cpu_in_madt(void)
diff --git a/arch/x86/include/asm/xen/hypervisor.h 
b/arch/x86/include/asm/xen/hypervisor.h
index 7048dfacc04b..a9088250770f 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -100,4 +100,13 @@ static inline void leave_lazy(enum xen_lazy_mode mode)
 
 enum xen_lazy_mode xen_get_lazy_mode(void);
 
+#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI)
+void xen_sanitize_proc_cap_bits(uint32_t *buf);
+#else
+static inline void xen_sanitize_proc_cap_bits(uint32_t *buf)
+{
+       BUG();
+}
+#endif
+
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
diff --git a/drivers/xen/pcpu.c b/drivers/xen/pcpu.c
index b3e3d1bb37f3..7000701dff8f 100644
--- a/drivers/xen/pcpu.c
+++ b/drivers/xen/pcpu.c
@@ -47,6 +47,9 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 
+#ifdef CONFIG_ACPI
+#include <acpi/processor.h>
+#endif
 
 /*
  * @cpu_id: Xen physical cpu logic number
@@ -400,4 +403,22 @@ bool __init xen_processor_present(uint32_t acpi_id)
 
        return online;
 }
+
+void xen_sanitize_proc_cap_bits(uint32_t *cap)
+{
+       struct xen_platform_op op = {
+               .cmd                    = XENPF_set_processor_pminfo,
+               .u.set_pminfo.id        = -1,
+               .u.set_pminfo.type      = XEN_PM_PDC,
+       };
+       u32 buf[3] = { ACPI_PDC_REVISION_ID, 1, *cap };
+       int ret;
+
+       set_xen_guest_handle(op.u.set_pminfo.pdc, buf);
+       ret = HYPERVISOR_platform_op(&op);
+       if (ret)
+               pr_err("sanitize of _PDC buffer bits from Xen failed: %d\n",
+                      ret);
+       *cap = buf[2];
+}
 #endif
-- 
2.41.0