Sorry, please ignore the last hyperv patch, I made a mistake. Zhao
On Mon, Oct 17, 2022 at 05:37:26PM +0800, Zhao Liu wrote: > Date: Mon, 17 Oct 2022 17:37:26 +0800 > From: Zhao Liu <zhao1....@linux.intel.com> > Subject: [PATCH v3] x86/hyperv: Replace kmap() with kmap_local_page() > X-Mailer: git-send-email 2.34.1 > > From: Zhao Liu <zhao1....@intel.com> > > kmap() is being deprecated in favor of kmap_local_page()[1]. > > There are two main problems with kmap(): (1) It comes with an overhead as > mapping space is restricted and protected by a global lock for > synchronization and (2) it also requires global TLB invalidation when the > kmap's pool wraps and it might block when the mapping space is fully utilized > until a slot becomes available. > > With kmap_local_page() the mappings are per thread, CPU local, can take page > faults, and can be called from any context (including interrupts). > It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the > tasks can be preempted and, when they are scheduled to run again, the kernel > virtual addresses are restored and are still valid. > > Since its use in hyperv/hv_init.c is safe, it should be preferred. > > Therefore, replace kmap() with kmap_local_page() in hyperv/hv_init.c. > > [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.we...@intel.com > > Suggested-by: Ira Weiny <ira.we...@intel.com> > Suggested-by: Fabio M. De Francesco <fmdefrance...@gmail.com> > Signed-off-by: Zhao Liu <zhao1....@intel.com> > > --- > Suggested by credits. > Ira: Referred to his task documentation and review comments. > Fabio: Stole some of his boiler plate commit message. > > --- > Changelog: > v2: > - Fix wrong incoming parameters in kunmap_local(); > - Add Fabio as suggester since I quoted his commit message. > > --- > arch/x86/hyperv/hv_init.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > index 3de6d8b53367..72fe46eb183f 100644 > --- a/arch/x86/hyperv/hv_init.c > +++ b/arch/x86/hyperv/hv_init.c > @@ -459,13 +459,13 @@ void __init hyperv_init(void) > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > > pg = vmalloc_to_page(hv_hypercall_pg); > - dst = kmap(pg); > + dst = kmap_local_page(pg); > src = memremap(hypercall_msr.guest_physical_address << > PAGE_SHIFT, PAGE_SIZE, > MEMREMAP_WB); > BUG_ON(!(src && dst)); > memcpy(dst, src, HV_HYP_PAGE_SIZE); > memunmap(src); > - kunmap(pg); > + kunmap_local(dst); > } else { > hypercall_msr.guest_physical_address = > vmalloc_to_pfn(hv_hypercall_pg); > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > -- > 2.34.1 >
