The root partition is not supposed to write to VP ASSIST PAGE as this MSR
is specific to Guest VP, and thus below stack is observed.
[ 2.778197] unchecked MSR access error: WRMSR to 0x40000073 (tried to write 0x0000000145ac5001) at rIP: 0xffffffff810c1084 (native_write_msr+0x4/0x30)
[ 2.784867] Call Trace:
[ 2.791507] hv_cpu_init+0xf1/0x1c0
[ 2.798144] ? hyperv_report_panic+0xd0/0xd0
[ 2.804806] cpuhp_invoke_callback+0x11a/0x440
[ 2.811465] ? hv_resume+0x90/0x90
[ 2.818137] cpuhp_issue_call+0x126/0x130
[ 2.824782] __cpuhp_setup_state_cpuslocked+0x102/0x2b0
[ 2.831427] ? hyperv_report_panic+0xd0/0xd0
[ 2.838075] ? hyperv_report_panic+0xd0/0xd0
[ 2.844723] ? hv_resume+0x90/0x90
[ 2.851375] __cpuhp_setup_state+0x3d/0x90
[ 2.858030] hyperv_init+0x14e/0x410
[ 2.864689] ? enable_IR_x2apic+0x190/0x1a0
[ 2.871349] apic_intr_mode_init+0x8b/0x100
[ 2.878017] x86_late_time_init+0x20/0x30
[ 2.884675] start_kernel+0x459/0x4fb
[ 2.891329] secondary_startup_64_no_verify+0xb0/0xbb
Root partition actually shares the VP ASSIST page with hypervisor, and
thus as a solution, this patch memremaps the memory from hypervisor
during hv_cpu_init and unmaps during hv_cpu_die calls.
Further, this patch also resolve some error handling and checkpatch
errors
Signed-off-by: Praveen Kumar <kumarpraveen@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/hyperv/hv_init.c | 57 +++++++++++++++++++++++++++------------
1 file changed, 40 insertions(+), 17 deletions(-)
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 6f247e7e07eb..292b17e0b173 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -44,7 +44,7 @@ EXPORT_SYMBOL_GPL(hv_vp_assist_page);
static int hv_cpu_init(unsigned int cpu)
{
- struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
+ struct hv_vp_assist_page **hvp = NULL;
int ret;
ret = hv_common_cpu_init(cpu);
@@ -54,25 +54,43 @@ static int hv_cpu_init(unsigned int cpu)
if (!hv_vp_assist_page)
return 0;
+ hvp = &hv_vp_assist_page[smp_processor_id()];
+
/*
- * The VP ASSIST PAGE is an "overlay" page (see Hyper-V TLFS's Section
- * 5.2.1 "GPA Overlay Pages"). Here it must be zeroed out to make sure
- * we always write the EOI MSR in hv_apic_eoi_write() *after* the
- * EOI optimization is disabled in hv_cpu_die(), otherwise a CPU may
- * not be stopped in the case of CPU offlining and the VM will hang.
+ * For Root partition we need to map the hypervisor VP ASSIST PAGE
+ * instead of allocating a new page.
*/
- if (!*hvp) {
- *hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
- }
+ if (hv_root_partition &&
+ ms_hyperv.features & HV_MSR_APIC_ACCESS_AVAILABLE) {
+ union hv_x64_msr_hypercall_contents hypercall_msr;
+
+ rdmsrl(HV_X64_MSR_VP_ASSIST_PAGE, hypercall_msr.as_uint64);
+ /* remapping to root partition address space */
+ *hvp = memremap(hypercall_msr.guest_physical_address <<
+ HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT,
+ PAGE_SIZE, MEMREMAP_WB);
+ WARN_ON(!(*hvp));
+ } else {
+ /*
+ * The VP ASSIST PAGE is an "overlay" page (see Hyper-V TLFS's
+ * Section 5.2.1 "GPA Overlay Pages"). Here it must be zeroed
+ * out to make sure we always write the EOI MSR in
+ * hv_apic_eoi_write() *after* the EOI optimization is disabled
+ * in hv_cpu_die(), otherwise a CPU may not be stopped in the
+ * case of CPU offlining and the VM will hang.
+ */
+ if (!*hvp)
+ *hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
- if (*hvp) {
- u64 val;
+ if (*hvp) {
+ u64 val;
- val = vmalloc_to_pfn(*hvp);
- val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) |
- HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;
+ val = vmalloc_to_pfn(*hvp);
+ val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) |
+ HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;
- wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
+ wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
+ }
}
return 0;
@@ -170,8 +188,13 @@ static int hv_cpu_die(unsigned int cpu)
hv_common_cpu_die(cpu);
- if (hv_vp_assist_page && hv_vp_assist_page[cpu])
- wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
+ if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
+ if (hv_root_partition &&
+ ms_hyperv.features & HV_MSR_APIC_ACCESS_AVAILABLE)
+ memunmap(hv_vp_assist_page[cpu]);
+ else
+ wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
+ }
if (hv_reenlightenment_cb == NULL)
return 0;
--
2.23.4
