On Thu, 27 May 2021 22:23:22 +0100, Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> wrote: > > On Thu, May 27, 2021 at 11:54 AM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > > > On Thu, 27 May 2021 16:05:11 +0100, > > Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> wrote: > > > > > > The hyp-stub's elx_sync code fits in the vector. > > > > > > With this, all of the hyp-stubs behaviour is contained in its vectors. > > > This lets kexec and hibernate copy the hyp-stub when they need its > > > behaviour, instead of re-implementing it. > > > > > > Co-developed-by: James Morse <james.morse@xxxxxxx> > > > Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > > > --- > > > arch/arm64/kernel/hyp-stub.S | 64 +++++++++++++++++++----------------- > > > 1 file changed, 33 insertions(+), 31 deletions(-) > > > > > > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > > > index 18a97bee3779..86af6c4e52b9 100644 > > > --- a/arch/arm64/kernel/hyp-stub.S > > > +++ b/arch/arm64/kernel/hyp-stub.S > > > @@ -21,6 +21,37 @@ SYM_CODE_START_LOCAL(\label) > > > .align 7 > > > b \label > > > SYM_CODE_END(\label) > > > +.endm > > > + > > > +.macro elx_sync_vector label > > > +SYM_CODE_START_LOCAL(\label) > > > + .align 7 > > > + cmp x0, #HVC_SET_VECTORS > > > + b.ne 1f > > > + msr vbar_el2, x1 > > > + b 9f > > > + > > > +1: cmp x0, #HVC_VHE_RESTART > > > + b.eq mutate_to_vhe > > > > Now that this has turned into a macro, what are the guarantees that > > mutate_to_vhe will be within reach of the site where this macro is > > expanded? It does work here, but what about the other expansion sites > > that will show up later in the series? > > > > What was wrong with directly branching to the original call site? > > Nothing in the commit message explains it. > > Hi Marc, > > I need to explain this better in the commit log. Later in the series > we create our own vector copy that is outside of the old and new > kernel so it does not get overwritten during kexec relocation. When > VHE is enabled, the vector is passed so we can switch to el2 before > jumping to the new kernel. > > arm64_relocate_new_kernel() which performs the relocation runs with > MMU being enabled until relocation is done, after that disables MMU > and if vectors are passed performs: > > mov x0, #HVC_SOFT_RESTART > hvc #0 /* Jumps from el2 */ > > It cannot call mutate_to_vhe because #HVC_VHE_RESTART is not used > here. But, if it had to it would not work as we cannot return to the > old kernel text after relocation. OK, so you are happy with having a dangling branch pointing to nowhere? Something in me screams that it isn't a good idea, in general. If HVC_SOFT_RESTART is all you need, I'd rather you have a small stub that implements exactly that and nothing else. Feel free to extract it as a reusable macro if you want. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
