Re: [PATCH v8 2/5] powerpc/hv-24x7: Add rtas call in hv-24x7 driver to get processor details
From: Nathan Lynch <hidden>
Date: 2020-05-11 21:10:13
Hi, Kajol Jain [off-list ref] writes:
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c index 48e8f4b17b91..8cf242aad98f 100644 --- a/arch/powerpc/perf/hv-24x7.c +++ b/arch/powerpc/perf/hv-24x7.c@@ -20,6 +20,7 @@ #include <asm/io.h> #include <linux/byteorder/generic.h> +#include <asm/rtas.h> #include "hv-24x7.h" #include "hv-24x7-catalog.h" #include "hv-common.h"@@ -57,6 +58,75 @@ static bool is_physical_domain(unsigned domain) } } +/* + * The Processor Module Information system parameter allows transferring + * of certain processor module information from the platform to the OS. + * Refer PAPR+ document to get parameter token value as '43'. + */ + +#define PROCESSOR_MODULE_INFO 43 +#define PROCESSOR_MAX_LENGTH (8 * 1024) + +DEFINE_SPINLOCK(rtas_local_data_buf_lock); +EXPORT_SYMBOL(rtas_local_data_buf_lock);
This should be static and not exported, correct?
+ +static u32 phys_sockets; /* Physical sockets */ +static u32 phys_chipspersocket; /* Physical chips per socket*/ +static u32 phys_coresperchip; /* Physical cores per chip */ + +/* + * Function read_sys_info_pseries() make a rtas_call which require + * data buffer of size 8K. As standard 'rtas_data_buf' is of size + * 4K, we are adding new local buffer 'rtas_local_data_buf'.
Sorry if this has been covered before but I don't understand why it would require a larger buffer; by my reading this call will return *ten bytes* of output. Also, current versions of PAPR+ limit the output length to 4002 bytes. I feel like I'm missing something.
+ */
+static __be16 rtas_local_data_buf[PROCESSOR_MAX_LENGTH] __cacheline_aligned;
+
+/*
+ * read_sys_info_pseries()
+ * Retrieve the number of sockets and chips per socket and cores per
+ * chip details through the get-system-parameter rtas call.
+ */
+void read_sys_info_pseries(void)
+{
+ int call_status, len, ntypes;
+
+ /*
+ * Making system parameter: chips and sockets and cores per chip
+ * default to 1.
+ */
+ phys_sockets = 1;
+ phys_chipspersocket = 1;
+ phys_coresperchip = 1;
+ memset(rtas_local_data_buf, 0, PROCESSOR_MAX_LENGTH * sizeof(__be16));Modifying global state outside of any critical section...? How do you prevent readers from seeing inconsistent results?
+ spin_lock(&rtas_local_data_buf_lock);
+
+ call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+ NULL,
+ PROCESSOR_MODULE_INFO,
+ __pa(rtas_local_data_buf),
+ PROCESSOR_MAX_LENGTH);
+
+ spin_unlock(&rtas_local_data_buf_lock);Using this lock this way fails to provide any protection to the data buffer or the phys_* variables.
+
+ if (call_status != 0) {
+ pr_info("Error calling get-system-parameter (0x%x)\n",
+ call_status);To be robust, this should handle busy (-2) and extended delay (990x) statuses. And if it's going to log errors it should use pr_err() and use decimal, not hex, to report the RTAS call status, since that's how they're specified in PAPR+.