Re: [PATCH] selftests: kvm: Mmap the entire vcpu mmap area

[Sean Christopherson <seanjc@google.com>]

On Wed, Feb 10, 2021, Aaron Lewis wrote:
> The vcpu mmap area may consist of more than just the kvm_run struct.
> Allocate enough space for the entire vcpu mmap area. Without this, on
> x86, the PIO page, for example, will be missing.  This is problematic
> when dealing with an unhandled exception from the guest as the exception
> vector will be incorrectly reported as 0x0.
> 
> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
> Signed-off-by: Steve Rutherford <srutherford@google.com>

Assuming Steve is the Co-author, this needs Co-developed-by.  And your SOB
should come after Steve's since, by virtue of sending the actual email, you're
the most recent handler of the patch.  See 'When to use Acked-by:, Cc:, and
Co-developed-by:' in Documentation/process/submitting-patches.rst.

  Co-developed-by: Steve Rutherford <srutherford@google.com>
  Signed-off-by: Steve Rutherford <srutherford@google.com>
  Signed-off-by: Aaron Lewis <aaronlewis@google.com>

> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index fa5a90e6c6f0..859a0b57c683 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -21,6 +21,8 @@
>  #define KVM_UTIL_PGS_PER_HUGEPG 512
>  #define KVM_UTIL_MIN_PFN	2
>  
> +static int vcpu_mmap_sz(void);

I'd vote to hoist the helper up instead of adding a forward declaration, but
either way works.

> +
>  /* Aligns x up to the next multiple of size. Size must be a power of 2. */
>  static void *align(void *x, size_t size)
>  {
> @@ -509,7 +511,7 @@ static void vm_vcpu_rm(struct kvm_vm *vm, struct vcpu *vcpu)
>  		vcpu->dirty_gfns = NULL;
>  	}
>  
> -	ret = munmap(vcpu->state, sizeof(*vcpu->state));
> +	ret = munmap(vcpu->state, vcpu_mmap_sz());
>  	TEST_ASSERT(ret == 0, "munmap of VCPU fd failed, rc: %i "
>  		"errno: %i", ret, errno);
>  	close(vcpu->fd);
> @@ -978,7 +980,7 @@ void vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid)
>  	TEST_ASSERT(vcpu_mmap_sz() >= sizeof(*vcpu->state), "vcpu mmap size "
>  		"smaller than expected, vcpu_mmap_sz: %i expected_min: %zi",
>  		vcpu_mmap_sz(), sizeof(*vcpu->state));
> -	vcpu->state = (struct kvm_run *) mmap(NULL, sizeof(*vcpu->state),
> +	vcpu->state = (struct kvm_run *) mmap(NULL, vcpu_mmap_sz(),
>  		PROT_READ | PROT_WRITE, MAP_SHARED, vcpu->fd, 0);
>  	TEST_ASSERT(vcpu->state != MAP_FAILED, "mmap vcpu_state failed, "
>  		"vcpu id: %u errno: %i", vcpuid, errno);
> -- 
> 2.30.0.478.g8a0d178c01-goog
>