On Wed, Oct 19, 2022 at 12:21:17AM +0800, Zhao Liu wrote:
> From: Zhao Liu <zhao1.liu@xxxxxxxxx>
>
> The commit 154fb14df7a3c ("x86/hyperv: Replace kmap() with
> kmap_local_page()") keeps the BUG_ON() to check if kmap_local_page()
> fails.
>
> But in fact, kmap_local_page() always returns a valid kernel address
> and won't return NULL here. It will BUG on its own if it fails. [1]
>
> So directly use memcpy_to_page() which creates local mapping to copy.
>
> [1]: https://lore.kernel.org/lkml/YztFEyUA48et0yTt@iweiny-mobl/
>
> Fixes: 154fb14df7a3 ("x86/hyperv: Replace kmap() with kmap_local_page()")
I don't know that a fixes is required here. We are not looking to backport any
of this and the other patch was correct. This is just a follow on cleanup.
> Suggested-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Code looks good. Without the fixes.
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Signed-off-by: Zhao Liu <zhao1.liu@xxxxxxxxx>
> ---
> arch/x86/hyperv/hv_init.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 29774126e931..f66c5709324f 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -459,13 +459,11 @@ void __init hyperv_init(void)
> wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
>
> pg = vmalloc_to_page(hv_hypercall_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);
> + BUG_ON(!src);
> + memcpy_to_page(pg, 0, src, HV_HYP_PAGE_SIZE);
> memunmap(src);
> - 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
>
