[Xen-changelog] [xen stable-4.12] x86/psr: fix bug which may cause crash

[patchbot@xxxxxxx]

commit cfc7ff1c6570188c3de738a472059fcc3786838c
Author:     Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
AuthorDate: Fri Dec 6 12:47:50 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Dec 6 12:47:50 2019 +0100

    x86/psr: fix bug which may cause crash
    
    During test, we found a crash on Xen with below trace.
    (XEN) Xen call trace:
    (XEN)    [<ffff82d0802a065a>] R psr.c#l3_cdp_write_msr+0x1e/0x22
    (XEN)    [<ffff82d0802a0858>] F psr.c#do_write_psr_msrs+0x6d/0x109
    (XEN)    [<ffff82d08023e000>] F smp_call_function_interrupt+0x5a/0xac
    (XEN)    [<ffff82d0802a2b89>] F call_function_interrupt+0x20/0x34
    (XEN)    [<ffff82d080282c64>] F do_IRQ+0x175/0x6ae
    (XEN)    [<ffff82d08038b8ba>] F common_interrupt+0x10a/0x120
    (XEN)    [<ffff82d0802ec616>] F cpu_idle.c#acpi_idle_do_entry+0x9d/0xb1
    (XEN)    [<ffff82d0802ecc01>] F cpu_idle.c#acpi_processor_idle+0x41d/0x626
    (XEN)    [<ffff82d08027353b>] F domain.c#idle_loop+0xa5/0xa7
    (XEN)
    (XEN)
    (XEN) ****************************************
    (XEN) Panic on CPU 20:
    (XEN) GENERAL PROTECTION FAULT
    (XEN) [error_code=0000]
    (XEN) ****************************************
    
    The bug happens when CDP and MBA co-exist and MBA COS_MAX is bigger
    than CDP COS_MAX. E.g. MBA has 8 COS registers but CDP only have 6.
    When setting MBA throttling value for the 7th guest, the value array
    would be:
        +------------------+------------------+--------------+
        | Data default val | Code default val | MBA throttle |
        +------------------+------------------+--------------+
    
    Then, COS id 7 will be selected for writting the values. We should
    avoid writting CDP data/code valules to COS id 7 MSR because it
    exceeds the CDP COS_MAX.
    
    Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 42c8cdc039d6dc7d6aea8008bb24622eaf4b7bc8
    master date: 2019-12-02 15:15:18 +0000
---
 xen/arch/x86/psr.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/arch/x86/psr.c b/xen/arch/x86/psr.c
index 5866a261e3..8bf1c23751 100644
--- a/xen/arch/x86/psr.c
+++ b/xen/arch/x86/psr.c
@@ -1269,6 +1269,17 @@ static void do_write_psr_msrs(void *data)
         cos_num = props->cos_num;
         ASSERT(info->array_len >= index + cos_num);
 
+        /*
+         * Multiple RDT features may co-exist and their COS_MAX may be
+         * different. So we should prevent one feature to write COS
+         * register which exceeds its COS_MAX.
+         */
+        if ( cos > feat->cos_max )
+        {
+            index += cos_num;
+            continue;
+        }
+
         for ( j = 0; j < cos_num; j++, index++ )
         {
             if ( feat->cos_reg_val[cos * cos_num + j] != info->val[index] )
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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