Hi
On 03/07/2016 11:41 PM, Paolo Bonzini wrote:
On 04/03/2016 21:46, Suravee Suthikulpanit wrote:
> [....]
+/* Note: This structure is per VM */
+struct svm_vm_data {
+ atomic_t count;
+ u32 ldr_mode;
+ u32 avic_max_vcpu_id;
+ u32 avic_tag;
+
+ struct page *avic_log_ait_page;
+ struct page *avic_phy_ait_page;
You can put these directly in kvm_arch. Do not use abbreviations:
struct page *avic_logical_apic_id_table_page;
struct page *avic_physical_apic_id_table_page;
Actually, the reason I would like to introduce this per-arch specific
structure is because I feel that it is easier to manage these
processor-specific variable/data-structure. If we add all these directly
into kvm_arch, which is shared b/w SVM and VMX, it is more difficult to
tell which one is used in the different code base.
[...]
+ memcpy(vapic_bkpg, svm->in_kernel_lapic_regs, PAGE_SIZE);
+ svm->vcpu.arch.apic->regs = vapic_bkpg;
Can you explain the flipping logic, and why you cannot just use the
existing apic.regs?
Please see "explanation 1" below.
[...]
+static struct svm_avic_phy_ait_entry *
+avic_get_phy_ait_entry(struct kvm_vcpu *vcpu, int index)
+{
+ [.....]
+}
+
+struct svm_avic_log_ait_entry *
+avic_get_log_ait_entry(struct kvm_vcpu *vcpu, u8 mda, bool is_flat)
+{
+ [.....]
+}
Instead of these functions, create a complete function to handle APIC_ID
and APIC_LDR writes. Then use kmap/kunmap instead of page_address.
Ok. May I ask why we are against using page_address? I have see that
used in several places in the code.
[...]
+static int avic_alloc_bk_page(struct vcpu_svm *svm, int id)
+{
+ int ret = 0, i;
+ bool realloc = false;
+ struct kvm_vcpu *vcpu;
+ struct kvm *kvm = svm->vcpu.kvm;
+ struct svm_vm_data *vm_data = kvm->arch.arch_data;
+
+ mutex_lock(&kvm->slots_lock);
+
+ /* Check if we have already allocated vAPIC backing
+ * page for this vCPU. If not, we need to realloc
+ * a new one and re-assign all other vCPU.
+ */
+ if (kvm->arch.apic_access_page_done &&
+ (id > vm_data->avic_max_vcpu_id)) {
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ avic_unalloc_bk_page(vcpu);
+
+ __x86_set_memory_region(kvm, APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
+ 0, 0);
+ realloc = true;
+ vm_data->avic_max_vcpu_id = 0;
+ }
+
+ /*
+ * We are allocating vAPIC backing page
+ * upto the max vCPU ID
+ */
+ if (id >= vm_data->avic_max_vcpu_id) {
+ ret = __x86_set_memory_region(kvm,
+ APIC_ACCESS_PAGE_PRIVATE_MEMSLOT,
+ APIC_DEFAULT_PHYS_BASE,
+ PAGE_SIZE * (id + 1));
Why is this necessary? The APIC access page is a peculiarity of Intel
processors (and the special memslot for only needs to map 0xfee00000 to
0xfee00fff; after that there is the MSI area).
Please see "explanation 1" below.
>> [...]
+ if (ret)
+ goto out;
+
+ vm_data->avic_max_vcpu_id = id;
+ }
+
+ /* Reinit vAPIC backing page for exisinting vcpus */
+ if (realloc)
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ avic_init_bk_page(vcpu);
Why is this necessary?
Explanation 1:
The current lapic regs page is allocated using get_zeroed_page(), which
can be paged out. If I use these pages for AVIC backing pages, it seems
to cause VM to slow down quite a bit due to a lot of page faults.
Currently, the AVIC backing pages are acquired from __x86_set_memory
region() with APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, which maps the pages for
address 0xfee00000 and above for VM to use. I mostly grab this from the
VMX implementation in alloc_apic_access_page().
However, the memslot requires specification of the size at the time when
calling __x86_set_memory_region(). However, I can't seem to figure out
where I can get the number of vcpus at the time when we creating VM.
Therefore, I have to track the vcpu creation, and re-acquire larger
memslot every time vcpu_create() is called.
I was not sure if this is the right approach, any suggestion for this part.
Thanks,
Suravee
