KVM: selftests: Adjust VM's initial stack address to align with SysV ABI spec

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Align the guest stack to match calling sequence requirements in
section "The Stack Frame" of the System V ABI AMD64 Architecture
Processor Supplement, which requires the value (%rsp + 8), NOT %rsp,
to be a multiple of 16 when control is transferred to the function
entry point. I.e. in a normal function call, %rsp needs to be 16-byte
aligned _before_ CALL, not after.

This fixes unexpected #GPs in guest code when the compiler uses SSE
instructions, e.g. to initialize memory, as many SSE instructions
require memory operands (including those on the stack) to be
16-byte-aligned.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Link: https://lore.kernel.org/r/20230227180601.104318-1-ackerleytng@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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Ackerley Tng 2023-02-27 18:06:01 +00:00 • committed by Sean Christopherson

parent 5b1abc285a

commit 8264e85560

1 changed files with 17 additions and 1 deletions

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tools/testing/selftests/kvm/lib/x86_64/processor.c

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