On 05/19/2017 07:09 AM, Vitaly Kuznetsov wrote:
Hyper-V host can suggest us to use hypercall for doing remote TLB flush,
this is supposed to work faster than IPIs.
Implementation details: to do HvFlushVirtualAddress{Space,List} hypercalls
we need to put the input somewhere in memory and we don't really want to
have memory allocation on each call so we pre-allocate per cpu memory areas
on boot. These areas are of fixes size, limit them with an arbitrary number
of 16 (16 gvas are able to specify 16 * 4096 pages).
pv_ops patching is happening very early so we need to separate
hyperv_setup_mmu_ops() and hyper_alloc_mmu().
It is possible and easy to implement local TLB flushing too and there is
even a hint for that. However, I don't see a room for optimization on the
host side as both hypercall and native tlb flush will result in vmexit. The
hint is also not set on modern Hyper-V versions.
Why do local flushes exit?
+static void hyperv_flush_tlb_others(const struct cpumask *cpus,
+ struct mm_struct *mm, unsigned long start,
+ unsigned long end)
+{
What tree will this go through? I'm about to send a signature change
for this function for tip:x86/mm.
Also, how would this interact with PCID? I have PCID patches that I'm
pretty happy with now, and I'm hoping to support PCID in 4.13.
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