Re: [PATCH 7/7] x86/HVM: drop stdvga's "vram_page[]" struct member

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 10/09/2024 3:41 pm, Jan Beulich wrote:
> No uses are left, hence its setup, teardown, and the field itself can
> also go away. stdvga_deinit() is then empty and can be dropped as well.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although I think
there's more to do.

> ---
> I have no idea whether in the tool stack some memory calculations would
> want adjusting, to account for the 256k less that a HVM domain now
> needs.

I honestly don't know.  We need dalloc() and friends, simply to figure
out whether it's a significant number or not.

> --- a/xen/arch/x86/include/asm/hvm/io.h
> +++ b/xen/arch/x86/include/asm/hvm/io.h
> @@ -111,12 +111,10 @@ struct vpci_arch_msix_entry {
>  };
>  
>  struct hvm_hw_stdvga {
> -    struct page_info *vram_page[64];  /* shadow of 0xa0000-0xaffff */
>      spinlock_t lock;
>  };

I'm pretty sure you can drop the lock too.  It's taken in accept(), and
dropped in complete(), but there's no state at all to be protected.

stdvga_mem_accept()'s return value is a simple expression of p.


With that dropped, the complete() handler disappears, and it's the only
hvm_io_ops->complete() handler in Xen so the whole field can go.

So I'm pretty sure there are 2 more patches that ought to be part of
this series, which go in a further negative direction.

~Andrew