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
> Subject: [PATCH v3] x86/hyperv: Replace kmap() with kmap_local_page()
> X-Mailer: git-send-email 2.34.1
>
> From: Zhao Liu
>
> 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
> Suggested-by: Fabio M. De Francesco
> Signed-off-by: Zhao Liu
>
> ---
> 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
>