Roman,
On 11/4/19 3:53 PM, Roman Kagan wrote:
On Fri, Nov 01, 2019 at 10:41:30PM +0000, Suthikulpanit, Suravee wrote:
Re-factor avic_init_access_page() to avic_update_access_page() since
activate/deactivate AVIC requires setting/unsetting the memory region used
for virtual APIC backing page (APIC_ACCESS_PAGE_PRIVATE_MEMSLOT).
AFAICT the patch actually touches the (de)allocation of the APIC access
page rather than the APIC backing page (or I'm confused in the
nomenclature).
The APIC backing page is allocated during vcpu initialization, while
the APIC_ACCESS_PAGE_PRIVATE_MEMSLOT, is initialized per-vm, and is
used mainly for access permission control of the APIC backing page.
There is a comment in the arch/x86/kvm/svm.c:
/**
* Note:
* AVIC hardware walks the nested page table to check permissions,
* but does not use the SPA address specified in the leaf page
* table entry since it uses address in the AVIC_BACKING_PAGE pointer
* field of the VMCB. Therefore, we set up the
* APIC_ACCESS_PAGE_PRIVATE_MEMSLOT (4KB) here.
*/
When deactivate APICv, we do not destroy the APIC backing page, but
we need to de-allocate the APIC_ACCESS_PAGE_PRIVATE_MEMSLOT.
Thanks,
Suravee
Thanks,
Roman.
