Re: [PATCH v5 1/8] s390/mm: force swiotlb for protected virtualization

[Michael Mueller <mimu@linux.ibm.com>]

On 12.06.19 13:12, Halil Pasic wrote:
> On s390, protected virtualization guests have to use bounced I/O
> buffers.  That requires some plumbing.
sed 's/  / /'

> 
> Let us make sure, any device that uses DMA API with direct ops correctly
> is spared from the problems, that a hypervisor attempting I/O to a
> non-shared page would bring.

That sentence reads pretty cumbersome.

> 
> Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>   arch/s390/Kconfig                   |  4 +++
>   arch/s390/include/asm/mem_encrypt.h | 18 +++++++++++
>   arch/s390/mm/init.c                 | 47 +++++++++++++++++++++++++++++
>   3 files changed, 69 insertions(+)
>   create mode 100644 arch/s390/include/asm/mem_encrypt.h
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 109243fdb6ec..88d8355b7bf7 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -1,4 +1,7 @@
>   # SPDX-License-Identifier: GPL-2.0
> +config ARCH_HAS_MEM_ENCRYPT
> +        def_bool y
> +
>   config MMU
>   	def_bool y
>   
> @@ -187,6 +190,7 @@ config S390
>   	select VIRT_CPU_ACCOUNTING
>   	select ARCH_HAS_SCALED_CPUTIME
>   	select HAVE_NMI
> +	select SWIOTLB
>   
>   
>   config SCHED_OMIT_FRAME_POINTER
> diff --git a/arch/s390/include/asm/mem_encrypt.h b/arch/s390/include/asm/mem_encrypt.h
> new file mode 100644
> index 000000000000..0898c09a888c
> --- /dev/null
> +++ b/arch/s390/include/asm/mem_encrypt.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef S390_MEM_ENCRYPT_H__
> +#define S390_MEM_ENCRYPT_H__
> +
> +#ifndef __ASSEMBLY__
> +
> +#define sme_me_mask	0ULL
> +
> +static inline bool sme_active(void) { return false; }
> +extern bool sev_active(void);
> +
> +int set_memory_encrypted(unsigned long addr, int numpages);
> +int set_memory_decrypted(unsigned long addr, int numpages);
> +
> +#endif	/* __ASSEMBLY__ */
> +
> +#endif	/* S390_MEM_ENCRYPT_H__ */
> +
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 14d1eae9fe43..f0bee6af3960 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -18,6 +18,7 @@
>   #include <linux/mman.h>
>   #include <linux/mm.h>
>   #include <linux/swap.h>
> +#include <linux/swiotlb.h>
>   #include <linux/smp.h>
>   #include <linux/init.h>
>   #include <linux/pagemap.h>
> @@ -29,6 +30,7 @@
>   #include <linux/export.h>
>   #include <linux/cma.h>
>   #include <linux/gfp.h>
> +#include <linux/dma-mapping.h>
>   #include <asm/processor.h>
>   #include <linux/uaccess.h>
>   #include <asm/pgtable.h>
> @@ -42,6 +44,8 @@
>   #include <asm/sclp.h>
>   #include <asm/set_memory.h>
>   #include <asm/kasan.h>
> +#include <asm/dma-mapping.h>
> +#include <asm/uv.h>
>   
>   pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>   
> @@ -128,6 +132,47 @@ 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)
> +{
> +	int i;
> +
> +	/* make specified pages unshared, (swiotlb, dma_free) */
> +	for (i = 0; i < numpages; ++i) {
> +		uv_remove_shared(addr);
> +		addr += PAGE_SIZE;
> +	}
> +	return 0;
> +}
> +
> +int set_memory_decrypted(unsigned long addr, int numpages)
> +{
> +	int i;
> +	/* make specified pages shared (swiotlb, dma_alloca) */
> +	for (i = 0; i < numpages; ++i) {
> +		uv_set_shared(addr);
> +		addr += PAGE_SIZE;
> +	}
> +	return 0;
> +}
> +
> +/* are we a protected virtualization guest? */
> +bool sev_active(void)
> +{
> +	return is_prot_virt_guest();
> +}
> +
> +/* protected virtualization */
> +static void pv_init(void)
> +{
> +	if (!is_prot_virt_guest())
> +		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);
> @@ -136,6 +181,8 @@ 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();
>   
> 

Reviewed-by: Michael Mueller <mimu@linux.ibm.com>

Michael