[Xen-changelog] [xen stable-4.2] x86/AMD: apply workaround for AMD F16h erratum 792

[patchbot@xxxxxxx]

commit 9bd0e75a2f31613e11455ea9cd4171741aecda68
Author:     Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>
AuthorDate: Thu Feb 13 10:17:40 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 13 10:17:40 2014 +0100

    x86/AMD: apply workaround for AMD F16h erratum 792
    
    Workaround for the Erratum will be in BIOSes spun only after
    Jan 2014 onwards. But initial production parts shipped in 2013
    itself. Since there is a coverage hole, we should carry this fix
    in software in case BIOS does not do the right thing or someone
    is using old BIOS.
    
    Description:
     Processor does not ensure DRAM scrub read/write sequence is atomic wrt
     accesses to CC6 save state area. Therefore if a concurrent scrub
     read/write access is to same address the entry may appear as if it is
     not written. This quirk applies to Fam16h models 00h-0Fh
    
    See "Revision Guide" for AMD F16h models 00h-0fh, document 51810 rev.
    3.04, Nov 2013.
    
    Equivalent Linux patch link:
     http://marc.info/?l=linux-kernel&m=139066012217149&w=2
    
    Tested the patch on Fam16h server platform and it works fine.
    
    Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>
    Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    
    Corrected checking for boot CPU. Made warning message conditional.
    Compacted warning message text. Moved comment to commit message.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 4d3ebb84df43d90db4cc25a48f4658709bd11678
    master date: 2014-02-07 11:12:22 +0100
---
 xen/arch/x86/cpu/amd.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index e20771b..3bb2dbd 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -523,6 +523,25 @@ static void __devinit init_amd(struct cpuinfo_x86 *c)
                       " all your (PV) guest kernels. ***\n");
 
        if (c->x86 == 0x16 && c->x86_model <= 0xf) {
+               if (c == &boot_cpu_data) {
+                       l = pci_conf_read32(0, 0, 0x18, 0x3, 0x58);
+                       h = pci_conf_read32(0, 0, 0x18, 0x3, 0x5c);
+                       if ((l & 0x1f) | (h & 0x1))
+                               printk(KERN_WARNING
+                                      "Applying workaround for erratum 792: 
%s%s%s\n",
+                                      (l & 0x1f) ? "clearing D18F3x58[4:0]" : 
"",
+                                      ((l & 0x1f) && (h & 0x1)) ? " and " : "",
+                                      (h & 0x1) ? "clearing D18F3x5C[0]" : "");
+
+                       if (l & 0x1f)
+                               pci_conf_write32(0, 0, 0x18, 0x3, 0x58,
+                                                l & ~0x1f);
+
+                       if (h & 0x1)
+                               pci_conf_write32(0, 0, 0x18, 0x3, 0x5c,
+                                                h & ~0x1);
+               }
+
                rdmsrl(MSR_AMD64_LS_CFG, value);
                if (!(value & (1 << 15))) {
                        static bool_t warned;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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