linux-kernel - [PATCH v2] powerpc/pseries: export LPAR security flavor in lparcfg

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Message-Id: <20210305125554.5165-1-ldufour@linux.ibm.com>
Date:   Fri,  5 Mar 2021 13:55:54 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org
Cc:     nathanl@...ux.ibm.com, cheloha@...ux.ibm.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] 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 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

Changes since V1:
 - Add details in the commit's description.

Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/powerpc/include/asm/hvcall.h        | 1 +
 arch/powerpc/platforms/pseries/lparcfg.c | 2 ++
 arch/powerpc/platforms/pseries/pseries.h | 1 +
 arch/powerpc/platforms/pseries/setup.c   | 8 ++++++++
 4 files changed, 12 insertions(+)

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index ed6086d57b22..455e188da26d 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/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
 
diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
index e278390ab28d..35f6c4929fbd 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c
@@ -169,6 +169,7 @@ static void show_gpci_data(struct seq_file *m)
 	kfree(buf);
 }
 
+
 static unsigned h_pic(unsigned long *pool_idle_time,
 		      unsigned long *num_procs)
 {
@@ -537,6 +538,7 @@ 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;
 }
 
diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
index 4fe48c04c6c2..a25517dc2515 100644
--- a/arch/powerpc/platforms/pseries/pseries.h
+++ b/arch/powerpc/platforms/pseries/pseries.h
@@ -111,6 +111,7 @@ 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);
 
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 46e1540abc22..59080413a269 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -85,6 +85,7 @@ 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)
 {
@@ -534,9 +535,16 @@ 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);
-- 
2.30.1