On 09/26/2015 09:50 PM, H. Peter Anvin wrote: > NAK. We really should map the GDT read-only on all 64 bit systems, > since we can't hide the address from SLDT. Same with the IDT. Sorry, I don't understand your point. > On September 26, 2015 11:00:40 AM PDT, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote: >> We have our GDT in a page-sized per-cpu structure, gdt_page. >> >> On x86_64 kernel, GDT is 128 bytes - only ~3% of that page is used. >> >> It is page-sized because of paravirt. Hypervisors need to know when >> GDT is changed, so they remap it read-only and handle write faults. >> If it's not in its own page, other writes nearby will cause >> those faults too. >> >> In other words, we need GDT to live in a separate page >> only if CONFIG_HYPERVISOR_GUEST=y. >> >> This patch reduces GDT alignment to cacheline-aligned >> if CONFIG_HYPERVISOR_GUEST is not set. >> >> Patch also renames gdt_page to cpu_gdt (mimicking naming of existing >> cpu_tss per-cpu variable), since now it is not always a full page. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
