diff options
Diffstat (limited to '0001-x86-hyperv-Suspend-resume-the-VP-assist-page-for-hib.patch')
| -rw-r--r-- | 0001-x86-hyperv-Suspend-resume-the-VP-assist-page-for-hib.patch | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/0001-x86-hyperv-Suspend-resume-the-VP-assist-page-for-hib.patch b/0001-x86-hyperv-Suspend-resume-the-VP-assist-page-for-hib.patch new file mode 100644 index 000000000..be667bd95 --- /dev/null +++ b/0001-x86-hyperv-Suspend-resume-the-VP-assist-page-for-hib.patch @@ -0,0 +1,92 @@ +From 421f090c819d695942a470051cd624dc43deaf95 Mon Sep 17 00:00:00 2001 +From: Dexuan Cui <decui@microsoft.com> +Date: Mon, 20 Apr 2020 19:46:11 -0700 +Subject: [PATCH] x86/hyperv: Suspend/resume the VP assist page for hibernation + +Unlike the other CPUs, CPU0 is never offlined during hibernation, so in the +resume path, the "new" kernel's VP assist page is not suspended (i.e. not +disabled), and later when we jump to the "old" kernel, the page is not +properly re-enabled for CPU0 with the allocated page from the old kernel. + +So far, the VP assist page is used by hv_apic_eoi_write(), and is also +used in the case of nested virtualization (running KVM atop Hyper-V). + +For hv_apic_eoi_write(), when the page is not properly re-enabled, +hvp->apic_assist is always 0, so the HV_X64_MSR_EOI MSR is always written. +This is not ideal with respect to performance, but Hyper-V can still +correctly handle this according to the Hyper-V spec; nevertheless, Linux +still must update the Hyper-V hypervisor with the correct VP assist page +to prevent Hyper-V from writing to the stale page, which causes guest +memory corruption and consequently may have caused the hangs and triple +faults seen during non-boot CPUs resume. + +Fix the issue by calling hv_cpu_die()/hv_cpu_init() in the syscore ops. +Without the fix, hibernation can fail at a rate of 1/300 ~ 1/500. +With the fix, hibernation can pass a long-haul test of 2000 runs. + +In the case of nested virtualization, disabling/reenabling the assist +page upon hibernation may be unsafe if there are active L2 guests. +It looks KVM should be enhanced to abort the hibernation request if +there is any active L2 guest. + +Fixes: 05bd330a7fd8 ("x86/hyperv: Suspend/resume the hypercall page for hibernation") +Cc: stable@vger.kernel.org +Signed-off-by: Dexuan Cui <decui@microsoft.com> +Link: https://lore.kernel.org/r/1587437171-2472-1-git-send-email-decui@microsoft.com +Signed-off-by: Wei Liu <wei.liu@kernel.org> +--- + arch/x86/hyperv/hv_init.c | 12 ++++++++++-- + 1 file changed, 10 insertions(+), 2 deletions(-) + +diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c +index 624f5d9b0f79..fd51bac11b46 100644 +--- a/arch/x86/hyperv/hv_init.c ++++ b/arch/x86/hyperv/hv_init.c +@@ -73,7 +73,8 @@ static int hv_cpu_init(unsigned int cpu) + struct page *pg; + + input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg); +- pg = alloc_page(GFP_KERNEL); ++ /* hv_cpu_init() can be called with IRQs disabled from hv_resume() */ ++ pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL); + if (unlikely(!pg)) + return -ENOMEM; + *input_arg = page_address(pg); +@@ -254,6 +255,7 @@ static int __init hv_pci_init(void) + static int hv_suspend(void) + { + union hv_x64_msr_hypercall_contents hypercall_msr; ++ int ret; + + /* + * Reset the hypercall page as it is going to be invalidated +@@ -270,12 +272,17 @@ static int hv_suspend(void) + hypercall_msr.enable = 0; + wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); + +- return 0; ++ ret = hv_cpu_die(0); ++ return ret; + } + + static void hv_resume(void) + { + union hv_x64_msr_hypercall_contents hypercall_msr; ++ int ret; ++ ++ ret = hv_cpu_init(0); ++ WARN_ON(ret); + + /* Re-enable the hypercall page */ + rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); +@@ -288,6 +295,7 @@ static void hv_resume(void) + hv_hypercall_pg_saved = NULL; + } + ++/* Note: when the ops are called, only CPU0 is online and IRQs are disabled. */ + static struct syscore_ops hv_syscore_ops = { + .suspend = hv_suspend, + .resume = hv_resume, +-- +2.26.2 + |