arm64: kernel: fix architected PMU registers unconditional access

commit f436b2ac90a095746beb6729b8ee8ed87c9eaede upstream.

The Performance Monitors extension is an optional feature of the
AArch64 architecture, therefore, in order to access Performance
Monitors registers safely, the kernel should detect the architected
PMU unit presence through the ID_AA64DFR0_EL1 register PMUVer field
before accessing them.

This patch implements a guard by reading the ID_AA64DFR0_EL1 register
PMUVer field to detect the architected PMU presence and prevent accessing
PMU system registers if the Performance Monitors extension is not
implemented in the core.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Fixes: 60792ad349f3 ("arm64: kernel: enforce pmuserenr_el0 initialization and restore")
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 23cfc08fc8ba88683600d7618acb9bdb400ae2b9..b685257926f0b0472550036f6d3ba34d17af7f62 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -512,9 +512,14 @@ CPU_LE(    movk    x0, #0x30d0, lsl #16    )       // Clear EE and E0E on LE systems
 #endif
 
        /* EL2 debug */
+       mrs     x0, id_aa64dfr0_el1             // Check ID_AA64DFR0_EL1 PMUVer
+       sbfx    x0, x0, #8, #4
+       cmp     x0, #1
+       b.lt    4f                              // Skip if no PMU present
        mrs     x0, pmcr_el0                    // Disable debug access traps
        ubfx    x0, x0, #11, #5                 // to EL2 and allow access to
        msr     mdcr_el2, x0                    // all PMU counters from EL1
+4:
 
        /* Stage-2 translation */
        msr     vttbr_el2, xzr

diff --git a/arch/arm64/mm/proc-macros.S b/arch/arm64/mm/proc-macros.S
index 4c4d93c4bf65b154fd0df25c4b8165593ff044be..d69dffffaa8993bc7260c1df035b92c3b3867b48 100644 (file)
--- a/arch/arm64/mm/proc-macros.S
+++ b/arch/arm64/mm/proc-macros.S
@@ -62,3 +62,15 @@
        bfi     \valreg, \tmpreg, #TCR_T0SZ_OFFSET, #TCR_TxSZ_WIDTH
 #endif
        .endm
+
+/*
+ * reset_pmuserenr_el0 - reset PMUSERENR_EL0 if PMUv3 present
+ */
+       .macro  reset_pmuserenr_el0, tmpreg
+       mrs     \tmpreg, id_aa64dfr0_el1        // Check ID_AA64DFR0_EL1 PMUVer
+       sbfx    \tmpreg, \tmpreg, #8, #4
+       cmp     \tmpreg, #1                     // Skip if no PMU present
+       b.lt    9000f
+       msr     pmuserenr_el0, xzr              // Disable PMU access from EL0
+9000:
+       .endm

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 9c4dce312b2b3b57a2335c17de60afca0515d675..b8f04b3f2786cc7ef29c1e47bf3bfec0f4bfc840 100644 (file)
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -117,7 +117,7 @@ ENTRY(cpu_do_resume)
         */
        ubfx    x11, x11, #1, #1
        msr     oslar_el1, x11
-       msr     pmuserenr_el0, xzr              // Disable PMU access from EL0
+       reset_pmuserenr_el0 x0                  // Disable PMU access from EL0
        mov     x0, x12
        dsb     nsh             // Make sure local tlb invalidation completed
        isb
@@ -156,7 +156,7 @@ ENTRY(__cpu_setup)
        msr     cpacr_el1, x0                   // Enable FP/ASIMD
        mov     x0, #1 << 12                    // Reset mdscr_el1 and disable
        msr     mdscr_el1, x0                   // access to the DCC from EL0
-       msr     pmuserenr_el0, xzr              // Disable PMU access from EL0
+       reset_pmuserenr_el0 x0                  // Disable PMU access from EL0
        /*
         * Memory region attributes for LPAE:
         *