[MODERATED] Re: [PATCH 1/2] L1TF KVM 1

[Dave Hansen <dave.hansen@intel.com>]

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>  	r = -ENOMEM;
> +	page = alloc_pages(GFP_ATOMIC, L1D_CACHE_ORDER);
> +	if (!page)
> +		goto out;
> +	empty_zero_pages = page_address(page);
> +

Couple more things:

PAGE_SIZE<<L1D_CACHE_ORDER is is only 32k, right?  The assembly sequence
clears 64k IIRC:

> +void kvm_l1d_flush(void)
> +{
> +	asm volatile(
> +		"movq %0, %%rax\n\t"
> +		"leaq 65536(%0), %%rdx\n\t"
> +		"11: \n\t"
...

So we probably want the allocation to be something like:

	l1d_clear_buf_size = PAGE_SIZE << (L1D_CACHE_ORDER+1) +
			     2 * PAGE_SIZE;
	alloc_pages_exact(l1d_clear_buf_size, GFP_ZERO|GFP_ATOMIC);

Note that we need GFP_ZERO because we could theoretically get a page
that already had kernel secrets in it.