Re: [PATCH 6.18 091/270] LoongArch: KVM: Compile switch.S directly into the kernel

[Sean Christopherson <seanjc@google.com>]

On Tue, May 12, 2026, Miguel Ojeda wrote:
> On Tue, 12 May 2026 19:38:12 +0200 Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> >
> > 6.18-stable review patch.  If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Xianglai Li <lixianglai@loongson.cn>
> >
> > commit 5203012fa6045aac4b69d4e7c212e16dcf38ef10 upstream.
> >
> > If we directly compile the switch.S file into the kernel, the address of
> > the kvm_exc_entry function will definitely be within the DMW memory area.
> > Therefore, we will no longer need to perform a copy relocation of the
> > kvm_exc_entry.
> >
> > So this patch compiles switch.S directly into the kernel, and then remove
> > the copy relocation execution logic for the kvm_exc_entry function.
> >
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Xianglai Li <lixianglai@loongson.cn>
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> For loongarch64, I am seeing a bunch of errors like:
> 
>     arch/loongarch/kvm/switch.S:201:1: error: unrecognized instruction mnemonic
>     EXPORT_SYMBOL_FOR_KVM(kvm_exc_entry)
>     ^
> 
> `EXPORT_SYMBOL_FOR_KVM` does not exist in 6.18. Does this need a subset
> of commit 6276c67f2bc4 ("x86: Restrict KVM-induced symbol exports to KVM
> modules where obvious/possible")?

Either that or just convert EXPORT_SYMBOL_FOR_KVM() => EXPORT_SYMBOL_GPL().  If
that's somewhat scriptable for ongoing LTS backports, that's probably the best
option.  EXPORT_SYMBOL_FOR_KVM() will only work for 6.18, and the list of backports
needed to get EXPORT_SYMBOL_FOR_MODULES() working on older LTS kernels looks to
be non-trivial

If we do end up backporting EXPORT_SYMBOL_FOR_KVM() and others, we might as well
also grab a subset of 01122b89361e ("perf: Use EXPORT_SYMBOL_FOR_KVM() for the
mediated APIs") to ensure a kvm_types.h stub is present on all archs.  That way
EXPORT_SYMBOL_FOR_KVM() usage in arch-neutral code will also work.

diff --git include/asm-generic/Kbuild include/asm-generic/Kbuild
index 295c94a3ccc1..9aff61e7b8f2 100644
--- include/asm-generic/Kbuild
+++ include/asm-generic/Kbuild
@@ -32,6 +32,7 @@ mandatory-y += irq_work.h
 mandatory-y += kdebug.h
 mandatory-y += kmap_size.h
 mandatory-y += kprobes.h
+mandatory-y += kvm_types.h
 mandatory-y += linkage.h
 mandatory-y += local.h
 mandatory-y += local64.h