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Date: Mon, 19 Mar 2018 09:51:46 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Christoph Hellwig <hch@....de>, x86@...nel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
David Woodhouse <dwmw2@...radead.org>,
Muli Ben-Yehuda <mulix@...ix.org>,
Jon Mason <jdmason@...zu.us>, Joerg Roedel <joro@...tes.org>,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/14] dma-direct: handle force decryption for dma
coherent buffers in common code
On 3/19/2018 5:38 AM, Christoph Hellwig wrote:
> With that in place the generic dma-direct routines can be used to
> allocate non-encrypted bounce buffers, and the x86 SEV case can use
> the generic swiotlb ops including nice features such as using CMA
> allocations.
>
> Note that I'm not too happy about using sev_active() in dma-direct, but
> I couldn't come up with a good enough name for a wrapper to make it
> worth adding.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> ---
> arch/x86/mm/mem_encrypt.c | 73 ++---------------------------------------------
> lib/dma-direct.c | 32 +++++++++++++++++----
> 2 files changed, 29 insertions(+), 76 deletions(-)
>
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 1a05bea831a8..65f45e0ef496 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -200,58 +200,6 @@ void __init sme_early_init(void)
> swiotlb_force = SWIOTLB_FORCE;
> }
>
> -static void *sev_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> - gfp_t gfp, unsigned long attrs)
> -{
> - unsigned int order;
> - struct page *page;
> - void *vaddr = NULL;
> -
> - order = get_order(size);
> - page = alloc_pages_node(dev_to_node(dev), gfp, order);
> - if (page) {
> - dma_addr_t addr;
> -
> - /*
> - * Since we will be clearing the encryption bit, check the
> - * mask with it already cleared.
> - */
> - addr = __phys_to_dma(dev, page_to_phys(page));
> - if ((addr + size) > dev->coherent_dma_mask) {
> - __free_pages(page, get_order(size));
> - } else {
> - vaddr = page_address(page);
> - *dma_handle = addr;
> - }
> - }
> -
> - if (!vaddr)
> - vaddr = swiotlb_alloc_coherent(dev, size, dma_handle, gfp);
> -
> - if (!vaddr)
> - return NULL;
> -
> - /* Clear the SME encryption bit for DMA use if not swiotlb area */
> - if (!is_swiotlb_buffer(dma_to_phys(dev, *dma_handle))) {
> - set_memory_decrypted((unsigned long)vaddr, 1 << order);
> - memset(vaddr, 0, PAGE_SIZE << order);
> - *dma_handle = __sme_clr(*dma_handle);
> - }
> -
> - return vaddr;
> -}
> -
> -static void sev_free(struct device *dev, size_t size, void *vaddr,
> - dma_addr_t dma_handle, unsigned long attrs)
> -{
> - /* Set the SME encryption bit for re-use if not swiotlb area */
> - if (!is_swiotlb_buffer(dma_to_phys(dev, dma_handle)))
> - set_memory_encrypted((unsigned long)vaddr,
> - 1 << get_order(size));
> -
> - swiotlb_free_coherent(dev, size, vaddr, dma_handle);
> -}
> -
> static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
> {
> pgprot_t old_prot, new_prot;
> @@ -404,20 +352,6 @@ bool sev_active(void)
> }
> EXPORT_SYMBOL(sev_active);
>
> -static const struct dma_map_ops sev_dma_ops = {
> - .alloc = sev_alloc,
> - .free = sev_free,
> - .map_page = swiotlb_map_page,
> - .unmap_page = swiotlb_unmap_page,
> - .map_sg = swiotlb_map_sg_attrs,
> - .unmap_sg = swiotlb_unmap_sg_attrs,
> - .sync_single_for_cpu = swiotlb_sync_single_for_cpu,
> - .sync_single_for_device = swiotlb_sync_single_for_device,
> - .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
> - .sync_sg_for_device = swiotlb_sync_sg_for_device,
> - .mapping_error = swiotlb_dma_mapping_error,
> -};
> -
> /* Architecture __weak replacement functions */
> void __init mem_encrypt_init(void)
> {
> @@ -428,12 +362,11 @@ void __init mem_encrypt_init(void)
> swiotlb_update_mem_attributes();
>
> /*
> - * With SEV, DMA operations cannot use encryption. New DMA ops
> - * are required in order to mark the DMA areas as decrypted or
> - * to use bounce buffers.
> + * With SEV, DMA operations cannot use encryption, we need to use
> + * SWIOTLB to bounce buffer DMA operation.
> */
> if (sev_active())
> - dma_ops = &sev_dma_ops;
> + dma_ops = &swiotlb_dma_ops;
>
> /*
> * With SEV, we need to unroll the rep string I/O instructions.
> diff --git a/lib/dma-direct.c b/lib/dma-direct.c
> index c9e8e21cb334..1277d293d4da 100644
> --- a/lib/dma-direct.c
> +++ b/lib/dma-direct.c
> @@ -9,6 +9,7 @@
> #include <linux/scatterlist.h>
> #include <linux/dma-contiguous.h>
> #include <linux/pfn.h>
> +#include <linux/set_memory.h>
>
> #define DIRECT_MAPPING_ERROR 0
>
> @@ -20,6 +21,14 @@
> #define ARCH_ZONE_DMA_BITS 24
> #endif
>
> +/*
> + * For AMD SEV all DMA must be to unencrypted addresses.
> + */
> +static inline bool force_dma_unencrypted(void)
> +{
> + return sev_active();
> +}
> +
> static bool
> check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
> const char *caller)
> @@ -37,7 +46,9 @@ check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
>
> static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
> {
> - return phys_to_dma(dev, phys) + size - 1 <= dev->coherent_dma_mask;
> + dma_addr_t addr = force_dma_unencrypted() ?
> + __phys_to_dma(dev, phys) : phys_to_dma(dev, phys);
> + return addr + size - 1 <= dev->coherent_dma_mask;
> }
>
> void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> @@ -46,6 +57,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> int page_order = get_order(size);
> struct page *page = NULL;
> + void *ret;
>
> /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
> if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
> @@ -78,10 +90,15 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>
> if (!page)
> return NULL;
> -
> - *dma_handle = phys_to_dma(dev, page_to_phys(page));
> - memset(page_address(page), 0, size);
> - return page_address(page);
> + ret = page_address(page);
> + if (force_dma_unencrypted()) {
> + set_memory_decrypted((unsigned long)ret, 1 << page_order);
> + *dma_handle = __phys_to_dma(dev, page_to_phys(page));
> + } else {
> + *dma_handle = phys_to_dma(dev, page_to_phys(page));
> + }
> + memset(ret, 0, size);
> + return ret;
> }
>
> /*
> @@ -92,9 +109,12 @@ void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
> dma_addr_t dma_addr, unsigned long attrs)
> {
> unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> + unsigned int page_order = get_order(size);
>
> + if (force_dma_unencrypted())
> + set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);
> if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
> - free_pages((unsigned long)cpu_addr, get_order(size));
> + free_pages((unsigned long)cpu_addr, page_order);
> }
>
> static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
>
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