Re: [kvm-unit-tests PATCH 1/2] arm64: set sctlr_el1.SPAN

[Andrew Jones <andrew.jones@linux.dev>]

On Fri, Jul 14, 2023 at 06:42:25PM +0000, Nadav Amit wrote:
> 
> 
> > On Jul 14, 2023, at 4:29 AM, Shaoqin Huang <shahuang@redhat.com> wrote:
> > 
> > !! External Email
> > 
> > Hi,
> > 
> > On 7/14/23 18:31, Alexandru Elisei wrote:
> >> Hi,
> >> 
> >> On Sat, Jun 17, 2023 at 01:31:37AM +0000, Nadav Amit wrote:
> >>> From: Nadav Amit <namit@vmware.com>
> >>> 
> >>> Do not assume PAN is not supported or that sctlr_el1.SPAN is already set.
> >> 
> >> In arm/cstart64.S
> >> 
> >> .globl start
> >> start:
> >>         /* get our base address */
> >>      [..]
> >> 
> >> 1:
> >>         /* zero BSS */
> >>      [..]
> >> 
> >>         /* zero and set up stack */
> >>      [..]
> >> 
> >>         /* set SCTLR_EL1 to a known value */
> >>         ldr     x4, =INIT_SCTLR_EL1_MMU_OFF
> >>      [..]
> >> 
> >>         /* set up exception handling */
> >>         bl      exceptions_init
> >>      [..]
> >> 
> >> Where in lib/arm64/asm/sysreg.h:
> >> 
> >> #define SCTLR_EL1_RES1  (_BITUL(7) | _BITUL(8) | _BITUL(11) | _BITUL(20) | \
> >>                          _BITUL(22) | _BITUL(23) | _BITUL(28) | _BITUL(29))
> >> #define INIT_SCTLR_EL1_MMU_OFF  \
> >>                         SCTLR_EL1_RES1
> >> 
> >> Look like bit 23 (SPAN) should be set.
> >> 
> >> How are you seeing SCTLR_EL1.SPAN unset?
> > 
> > Yeah. the sctlr_el1.SPAN has always been set by the above flow. So Nadav
> > you can describe what you encounter with more details. Like which tests
> > crash you encounter, and how to reproduce it.
> 
> I am using Nikos’s work to run the test using EFI, not from QEMU.
> 
> So the code that you mentioned - which is supposed to initialize SCTLR -
> is not executed (and actually not part of the EFI image).
> 
> Note that using EFI, the entry point is _start [1], and not “start”.
> 
> That is also the reason lack of BSS zeroing also caused me issues with the
> EFI setup, which I reported before.

Nadav,

Would you mind reposting this along with the BSS zeroing patch, the
way I proposed we do that, and anything else you've discovered when
trying to use the EFI unit tests without QEMU? We'll call that our
first non-QEMU EFI support series, since the first EFI series was
only targeting QEMU.

Thanks,
drew

> 
> 
> 
> [1] https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/blob/master/arm/efi/crt0-efi-aarch64.S#L113
>