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@runbox.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Andy Lutomirski luto@kernel.org Cc: Ingo Molnar mingo@redhat.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Juergen Gross jgross@suse.com Cc: xen-devel@lists.xenproject.org Cc: x86@kernel.org Cc: stable@vger.kernel.org # for v4.17 and up Fixes: d94a155c59c9 ("x86/cpu: Prevent cpuinfo_x86::x86_phys_bits adjustment corruption")
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Changes since v1: - Move the call to get_cpu_address_sizes below the call to x86_configure_nx. - Amend the commit message to describe why PV VMs do not boot up successfully when CONFIG_DEBUG_VIRTUAL is enabled.
Changes since v2: - Add a Reviewed-by tag to note Boris Ostrovsky's code review. - Rebase onto next-20180725. --- 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(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index f73fa6f6d85e..dd282482de09 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -911,7 +911,7 @@ 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;
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h index 38216f678fc3..12a5f0cec0b2 100644 --- 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_cpu_dev_start[], *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 void init_scattered_cpuid_features(struct cpuinfo_x86 *c); extern u32 get_scattered_cpuid_leaf(unsigned int level, diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 105a57d73701..ee3b00c7acda 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1256,6 +1256,9 @@ asmlinkage __visible void __init xen_start_kernel(void) 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;