On Mon, 2025-07-21 at 17:44 -0700, H. Peter Anvin wrote: > On July 21, 2025 4:42:22 PM PDT, "Huang, Kai" <kai.huang@xxxxxxxxx> wrote: > > On Mon, 2025-07-21 at 23:29 +0000, Huang, Kai wrote: > > > > On July 21, 2025 2:36:48 PM PDT, "Huang, Kai" <kai.huang@xxxxxxxxx> wrote: > > > > > On Mon, 2025-07-21 at 16:27 -0500, Tom Lendacky wrote: > > > > > > > > > @@ -204,7 +202,7 @@ > > > > SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) > > > > > > > > > * entries that will conflict with the now unencrypted memory > > > > > > > > > * used by kexec. Flush the caches before copying the kernel. > > > > > > > > > */ > > > > > > > > > - testq %r8, %r8 > > > > > > > > > + testq $RELOC_KERNEL_HOST_MEM_ACTIVE, %r11 > > > > > > > > > > > > > > > > Hmmm... can't both bits be set at the same time? If so, then this > > > > > > > > will fail. This should be doing bit tests now. > > > > > > > > > > > > > > TEST instruction performs logical AND of the two operands, > > > > > > > therefore the above equals to: > > > > > > > > > > > > > > set ZF if "R11 AND BIT(1) == 0". > > > > > > > > > > > > > > Whether there's any other bits set in R11 doesn't impact the above, right? > > > > > > > > > > > > > > > > > > > Doh! My bad, yes, not sure what I was thinking there. > > > > > > > > > > > > > > > > Np and thanks! I'll address your other comments but I'll see whether > > > > > Boris has any other comments first. > > > > > > > > > > > > > You can use testb in this case to save 3 bytes, too. > > > > > > Yeah I can do that, thanks for the info! > > > > I just tried. I need to do: > > > > testb $RELOC_KERNEL_HOST_MEM_ACTIVE, %r11b > > > > in order to compile, otherwise using plain %r11 generates: > > > > arch/x86/kernel/relocate_kernel_64.S:212: Error: `%r11' not allowed with > > `testb' > > > > I'll do some test and if there's no problem I'll switch to use this way, > > assuming it still saves us 3-bytes. > > > > That works just fine. Yeah I have now tested. Thanks :-)
