| Message ID | 20230227180601.104318-1-ackerleytng@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/1] KVM: selftests: Adjust VM's initial stack address to align with SysV ABI spec | expand |
On Mon, 27 Feb 2023 18:06:01 +0000, Ackerley Tng wrote: > 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. > > [...] Applied to kvm-x86 selftests, thanks! [1/1] KVM: selftests: Adjust VM's initial stack address to align with SysV ABI spec https://github.com/kvm-x86/linux/commit/1982754bd2a7 -- https://github.com/kvm-x86/linux/tree/next https://github.com/kvm-x86/linux/tree/fixes
On Fri, Mar 24, 2023, Sean Christopherson wrote: > On Mon, 27 Feb 2023 18:06:01 +0000, Ackerley Tng wrote: > > 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. > > > > [...] > > Applied to kvm-x86 selftests, thanks! > > [1/1] KVM: selftests: Adjust VM's initial stack address to align with SysV ABI spec > https://github.com/kvm-x86/linux/commit/1982754bd2a7 Force pushed to selftests 'cause I had a goof, this now: KVM: selftests: Adjust VM's initial stack address to align with SysV ABI spec https://github.com/kvm-x86/linux/commit/8264e85560e5
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c index ae1e573d94ce..a0669d31bb85 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c @@ -5,6 +5,7 @@ * Copyright (C) 2018, Google LLC. */ +#include "linux/bitmap.h" #include "test_util.h" #include "kvm_util.h" #include "processor.h" @@ -573,6 +574,21 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id, DEFAULT_GUEST_STACK_VADDR_MIN, MEM_REGION_DATA); + stack_vaddr += DEFAULT_STACK_PGS * getpagesize(); + + /* + * Align 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) to be a multiple of + * 16 when control is transferred to the function entry point. + * + * If this code is ever used to launch a vCPU with 32-bit entry point it + * may need to subtract 4 bytes instead of 8 bytes. + */ + TEST_ASSERT(IS_ALIGNED(stack_vaddr, PAGE_SIZE), + "__vm_vaddr_alloc() did not provide a page-aligned address"); + stack_vaddr -= 8; + vcpu = __vm_vcpu_add(vm, vcpu_id); vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid()); vcpu_setup(vm, vcpu); @@ -580,7 +596,7 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id, /* Setup guest general purpose registers */ vcpu_regs_get(vcpu, ®s); regs.rflags = regs.rflags | 0x2; - regs.rsp = stack_vaddr + (DEFAULT_STACK_PGS * getpagesize()); + regs.rsp = stack_vaddr; regs.rip = (unsigned long) guest_code; vcpu_regs_set(vcpu, ®s);
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> --- This patch is a follow-up from discussions at https://lore.kernel.org/lkml/20230121001542.2472357-9-ackerleytng@google.com/ v1 -> v2: Cleaned the patch up after getting comments from Sean in v1: https://lore.kernel.org/lkml/Y%2FfHLdvKHlK6D%2F1v@google.com/ Please also see https://lore.kernel.org/lkml/20230227174654.94641-1-ackerleytng@google.com/ regarding providing alignment macros for selftests. --- .../selftests/kvm/lib/x86_64/processor.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) -- 2.39.2.722.g9855ee24e9-goog