Re: [RFC PATCH 03/12] s390/mm: force swiotlb for protected virtualization

Cornelia Huck
2019-04-09T10:16:47Z

On Fri, 5 Apr 2019 01:16:13 +0200
Halil Pasic <pasic@linux.ibm.com> wrote:

> On s390 protected virtualization guests also have to use bounce I/O
> buffers. That requires some plumbing.
>
> Let us make sure any device using DMA API accordingly is spared from the
> problems that hypervisor attempting I/O to a non-shared secure page would
> bring.

I have problems parsing this sentence :(

Do you mean that we want to exclude pages for I/O from encryption?

>
> Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> ---
> arch/s390/Kconfig | 4 ++++
> arch/s390/include/asm/Kbuild | 1 -
> arch/s390/include/asm/dma-mapping.h | 13 +++++++++++
> arch/s390/include/asm/mem_encrypt.h | 18 +++++++++++++++
> arch/s390/mm/init.c | 44 +++++++++++++++++++++++++++++++++++++
> 5 files changed, 79 insertions(+), 1 deletion(-)
> create mode 100644 arch/s390/include/asm/dma-mapping.h
> create mode 100644 arch/s390/include/asm/mem_encrypt.h

(...)

> @@ -126,6 +129,45 @@ void mark_rodata_ro(void)
> pr_info("Write protected read-only-after-init data: %luk\n", size >> 10);
> }
>
> +int set_memory_encrypted(unsigned long addr, int numpages)
> +{
> + /* also called for the swiotlb bounce buffers, make all pages shared */
> + /* TODO: do ultravisor calls */
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(set_memory_encrypted);
> +
> +int set_memory_decrypted(unsigned long addr, int numpages)
> +{
> + /* also called for the swiotlb bounce buffers, make all pages shared */
> + /* TODO: do ultravisor calls */
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(set_memory_decrypted);
> +
> +/* are we a protected virtualization guest? */
> +bool sev_active(void)
> +{
> + /*
> + * TODO: Do proper detection using ultravisor, for now let us fake we
> + * have it so the code gets exercised.

That's the swiotlb stuff, right?

(The patches will obviously need some reordering before it is actually
getting merged.)

> + */
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(sev_active);
> +
> +/* protected virtualization */
> +static void pv_init(void)
> +{
> + if (!sev_active())
> + return;
> +
> + /* make sure bounce buffers are shared */
> + swiotlb_init(1);
> + swiotlb_update_mem_attributes();
> + swiotlb_force = SWIOTLB_FORCE;
> +}
> +
> void __init mem_init(void)
> {
> cpumask_set_cpu(0, &init_mm.context.cpu_attach_mask);
> @@ -134,6 +176,8 @@ void __init mem_init(void)
> set_max_mapnr(max_low_pfn);
> high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
>
> + pv_init();
> +
> /* Setup guest page hinting */
> cmma_init();
>