powerpc/pseries: export LPAR security flavor in lparcfg

This is helpful to read the security flavor from inside the LPAR.

In /sys/kernel/debug/powerpc/security_features it can be seen if
mitigations are on or off but not the level set through the ASMI menu.
Furthermore, reporting it through /proc/powerpc/lparcfg allows an easy
processing by the lparstat command [1].

Export it like this in /proc/powerpc/lparcfg:

  $ grep security_flavor /proc/powerpc/lparcfg
  security_flavor=1

Value follows what is documented on the IBM support page [2]:

  0 Speculative execution fully enabled
  1 Speculative execution controls to mitigate user-to-kernel attacks
  2 Speculative execution controls to mitigate user-to-kernel and
    user-to-user side-channel attacks

[1] https://groups.google.com/g/powerpc-utils-devel/c/NaKXvdyl_UI/m/wa2stpIDAQAJ
[2] https://www.ibm.com/support/pages/node/715841

Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210305125554.5165-1-ldufour@linux.ibm.com

arch/powerpc/include/asm/hvcall.h

@@ -389,6 +389,7 @@
 #define H_CPU_BEHAV_FAVOUR_SECURITY	(1ull << 63) // IBM bit 0
 #define H_CPU_BEHAV_L1D_FLUSH_PR	(1ull << 62) // IBM bit 1
 #define H_CPU_BEHAV_BNDS_CHK_SPEC_BAR	(1ull << 61) // IBM bit 2
+#define H_CPU_BEHAV_FAVOUR_SECURITY_H	(1ull << 60) // IBM bit 3
 #define H_CPU_BEHAV_FLUSH_COUNT_CACHE	(1ull << 58) // IBM bit 5
 #define H_CPU_BEHAV_FLUSH_LINK_STACK	(1ull << 57) // IBM bit 6
 

arch/powerpc/platforms/pseries/lparcfg.c

@@ -537,6 +537,8 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v)
 	parse_em_data(m);
 	maxmem_data(m);
 
+	seq_printf(m, "security_flavor=%u\n", pseries_security_flavor);
+
 	return 0;
 }
 

arch/powerpc/platforms/pseries/pseries.h

@@ -108,6 +108,7 @@ static inline unsigned long cmo_get_page_size(void)
 
 int dlpar_workqueue_init(void);
 
+extern u32 pseries_security_flavor;
 void pseries_setup_security_mitigations(void);
 void pseries_lpar_read_hblkrm_characteristics(void);
 

arch/powerpc/platforms/pseries/setup.c

@@ -86,6 +86,7 @@ EXPORT_SYMBOL(CMO_PageSize);
 
 int fwnmi_active;  /* TRUE if an FWNMI handler is present */
 int ibm_nmi_interlock_token;
+u32 pseries_security_flavor;
 
 static void pSeries_show_cpuinfo(struct seq_file *m)
 {
@@ -535,9 +536,15 @@ static void init_cpu_char_feature_flags(struct h_cpu_char_result *result)
 	/*
 	 * The features below are enabled by default, so we instead look to see
 	 * if firmware has *disabled* them, and clear them if so.
+	 * H_CPU_BEHAV_FAVOUR_SECURITY_H could be set only if
+	 * H_CPU_BEHAV_FAVOUR_SECURITY is.
 	 */
 	if (!(result->behaviour & H_CPU_BEHAV_FAVOUR_SECURITY))
 		security_ftr_clear(SEC_FTR_FAVOUR_SECURITY);
+	else if (result->behaviour & H_CPU_BEHAV_FAVOUR_SECURITY_H)
+		pseries_security_flavor = 1;
+	else
+		pseries_security_flavor = 2;
 
 	if (!(result->behaviour & H_CPU_BEHAV_L1D_FLUSH_PR))
 		security_ftr_clear(SEC_FTR_L1D_FLUSH_PR);