On Tue, Apr 12, 2022, Varad Gautam wrote: > UEFI test builds currently use the stack pointer configured by the > UEFI implementation. > > Reserve stack space in .data for EFI testcases and switch %rsp to > use this memory on early boot. This provides one 4K page per CPU > to store its stack / percpu data. > > Signed-off-by: Varad Gautam <varad.gautam@xxxxxxxx> > --- > x86/efi/crt0-efi-x86_64.S | 3 +++ > x86/efi/efistart64.S | 8 ++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/x86/efi/crt0-efi-x86_64.S b/x86/efi/crt0-efi-x86_64.S > index eaf1656..1708ed5 100644 > --- a/x86/efi/crt0-efi-x86_64.S > +++ b/x86/efi/crt0-efi-x86_64.S > @@ -58,6 +58,9 @@ _start: > popq %rdi > popq %rsi > > + /* Switch away from EFI stack. */ > + lea stacktop(%rip), %rsp > + > call efi_main > addq $8, %rsp > > diff --git a/x86/efi/efistart64.S b/x86/efi/efistart64.S > index 8eadca5..cb08230 100644 > --- a/x86/efi/efistart64.S > +++ b/x86/efi/efistart64.S > @@ -6,6 +6,14 @@ > > .data > > +max_cpus = MAX_TEST_CPUS Why declare max_cpus? MAX_TEST_CPUS can be used directly. > + Rather than align the stack top, wouldn't it be easier and more obvious to the reader to pre-align to? .align PAGE_SIZE > +/* Reserve stack in .data */ > + . = . + 4096 * max_cpus Use PAGE_SIZE instead of open coding 4096. E.g. this works for me with my MSR_GS_BASE suggestion in the next patch (spoiler alert). /* Reserve stack in .data */ .data .align PAGE_SIZE . = . + PAGE_SIZE * MAX_TEST_CPUS .globl stacktop stacktop: > + .align 16 > +.globl stacktop > +stacktop: > + > .align PAGE_SIZE > .globl ptl2 > ptl2: > -- > 2.32.0 >
