[Xen-devel] Patch "xen/pv: Call get_cpu_address_sizes to set x86_virt/phys_bits" has been added to the 4.17-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    xen/pv: Call get_cpu_address_sizes to set x86_virt/phys_bits

to the 4.17-stable tree which can be found at:
    
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xen-pv-call-get_cpu_address_sizes-to-set-x86_virt-phys_bits.patch
and it can be found in the queue-4.17 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


From 405c018a25fe464dc68057bbc8014a58f2bd4422 Mon Sep 17 00:00:00 2001
From: "M. Vefa Bicakci" <m.v.b@xxxxxxxxxx>
Date: Tue, 24 Jul 2018 08:45:47 -0400
Subject: xen/pv: Call get_cpu_address_sizes to set x86_virt/phys_bits

From: M. Vefa Bicakci <m.v.b@xxxxxxxxxx>

commit 405c018a25fe464dc68057bbc8014a58f2bd4422 upstream.

Commit d94a155c59c9 ("x86/cpu: Prevent cpuinfo_x86::x86_phys_bits
adjustment corruption") has moved the query and calculation of the
x86_virt_bits and x86_phys_bits fields of the cpuinfo_x86 struct
from the get_cpu_cap function to a new function named
get_cpu_address_sizes.

One of the call sites related to Xen PV VMs was unfortunately missed
in the aforementioned commit. This prevents successful boot-up of
kernel versions 4.17 and up in Xen PV VMs if CONFIG_DEBUG_VIRTUAL
is enabled, due to the following code path:

  enlighten_pv.c::xen_start_kernel
    mmu_pv.c::xen_reserve_special_pages
      page.h::__pa
        physaddr.c::__phys_addr
          physaddr.h::phys_addr_valid

phys_addr_valid uses boot_cpu_data.x86_phys_bits to validate physical
addresses. boot_cpu_data.x86_phys_bits is no longer populated before
the call to xen_reserve_special_pages due to the aforementioned commit
though, so the validation performed by phys_addr_valid fails, which
causes __phys_addr to trigger a BUG, preventing boot-up.

Signed-off-by: M. Vefa Bicakci <m.v.b@xxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # for v4.17 and up
Fixes: d94a155c59c9 ("x86/cpu: Prevent cpuinfo_x86::x86_phys_bits adjustment 
corruption")
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kernel/cpu/common.c |    2 +-
 arch/x86/kernel/cpu/cpu.h    |    1 +
 arch/x86/xen/enlighten_pv.c  |    3 +++
 3 files changed, 5 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -883,7 +883,7 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
        apply_forced_caps(c);
 }
 
-static void get_cpu_address_sizes(struct cpuinfo_x86 *c)
+void get_cpu_address_sizes(struct cpuinfo_x86 *c)
 {
        u32 eax, ebx, ecx, edx;
 
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -46,6 +46,7 @@ extern const struct cpu_dev *const __x86
                            *const __x86_cpu_dev_end[];
 
 extern void get_cpu_cap(struct cpuinfo_x86 *c);
+extern void get_cpu_address_sizes(struct cpuinfo_x86 *c);
 extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
 extern int detect_extended_topology_early(struct cpuinfo_x86 *c);
 extern int detect_ht_early(struct cpuinfo_x86 *c);
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1258,6 +1258,9 @@ asmlinkage __visible void __init xen_sta
        get_cpu_cap(&boot_cpu_data);
        x86_configure_nx();
 
+       /* Determine virtual and physical address sizes */
+       get_cpu_address_sizes(&boot_cpu_data);
+
        /* Let's presume PV guests always boot on vCPU with id 0. */
        per_cpu(xen_vcpu_id, 0) = 0;
 


Patches currently in stable-queue which might be from m.v.b@xxxxxxxxxx are

queue-4.17/xen-pv-call-get_cpu_address_sizes-to-set-x86_virt-phys_bits.patch

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