Messages in this thread | | | Date | Tue, 19 Jul 2022 19:13:54 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH v8 4/5] x86/mm: Add noalias variants of set_memory_*crypted() functions |
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On Mon, Jul 18, 2022 at 07:22:52AM -0700, Sathyanarayanan Kuppuswamy wrote: > Hi Dave, > > On 7/5/22 8:29 AM, Kirill A. Shutemov wrote: > >>> I still don't like the idea of using the DMA API itself. But, maybe we > >>> need some common infrastructure that the DMA API and this code use which > >>> says, "get me some pages that I can safely make shared". > >> Right. For instance any KVM PV feature would require shared memory, and DMA API > >> normally doesn't fit (taking 'struct kvm_steal_time' as example). > >> > >> Maybe we can reserve a CMA for this purpose. > > CMA for couple low traffic users sounds like an overkill. It will create > > an separate pool just for them. > > > > I think the best way is to add an dummy device and couple of helpers > > around DMA API that would allow to tap into swiotlb. > > > > Maybe hide it inside CC infrastructure. Like cc_decrypted_alloc() and > > cc_decrypted_free(). > > I also think creating a generic device in the CC layer, and using it to allocate > memory via DMA APIs is a better approach for this issue. Following is the sample > implementation to give you an idea on how it looks. Please let me know > your comments. > > cc_shmem_alloc/free() APIs can be used by CC users to allocate and > free shared memory.
We usually use 'decrypted' term in kernel. cc_decrypted_alloc()/_free().
> Other vendors can define their own shared memory allocation and free > logic via struct shmem_priv alloc/free/init hooks. > > --- a/arch/x86/coco/Makefile > +++ b/arch/x86/coco/Makefile > @@ -3,6 +3,6 @@ CFLAGS_REMOVE_core.o = -pg > KASAN_SANITIZE_core.o := n > CFLAGS_core.o += -fno-stack-protector > > -obj-y += core.o > +obj-y += core.o shmem.o
Rename shmem.o -> mem.o ?
> diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c > index 49b44f881484..62fe68d1f60a 100644 > --- a/arch/x86/coco/core.c > +++ b/arch/x86/coco/core.c > @@ -13,7 +13,7 @@ > #include <asm/coco.h> > #include <asm/processor.h> > > -static enum cc_vendor vendor __ro_after_init; > +enum cc_vendor vendor __ro_after_init; > static u64 cc_mask __ro_after_init; > > static bool intel_cc_platform_has(enum cc_attr attr) > @@ -23,6 +23,7 @@ static bool intel_cc_platform_has(enum cc_attr attr) > case CC_ATTR_HOTPLUG_DISABLED: > case CC_ATTR_GUEST_MEM_ENCRYPT: > case CC_ATTR_MEM_ENCRYPT: > + case CC_ATTR_SHMEM: > return true; > default: > return false;
I don't think we need a new attribute. CC_ATTR_MEM_ENCRYPT has to be enough.
> @@ -134,6 +135,11 @@ __init void cc_set_vendor(enum cc_vendor v) > vendor = v; > } > > +enum cc_vendor cc_get_vendor(void) > +{ > + return vendor; > +} > + > __init void cc_set_mask(u64 mask) > { > cc_mask = mask; > > +++ b/arch/x86/coco/shmem.c > @@ -0,0 +1,156 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Confidential Computing Shared Memory Allocator > + * > + * Copyright (C) 2022 Intel Corporation, Inc. > + * > + */ > + > +#undef pr_fmt > +#define pr_fmt(fmt) "CC: " fmt > + > +#include <linux/export.h> > +#include <linux/cma.h> > +#include <linux/mm.h> > +#include <linux/cc_platform.h> > +#include <linux/set_memory.h> > +#include <linux/platform_device.h> > +#include <linux/dma-mapping.h> > + > +#include <asm/coco.h> > +#include <asm/processor.h> > + > +#define CC_SHMEM_DRIVER "cc-shmem" > + > +struct platform_device *shmem_pdev; > + > +struct shmem_priv > +{ > + int (*init)(struct platform_device *dev); > + void* (*alloc)(size_t size, gfp_t gfp, struct shmem_priv *priv); > + void (*free)(void *addr, size_t size, struct shmem_priv *priv); > + struct platform_device *pdev; > + void *data; > +}; > + > +void *cc_shmem_alloc(size_t size, gfp_t gfp) > +{ > + struct shmem_priv *priv; > + > + if (!shmem_pdev) > + return NULL; > + > + priv = platform_get_drvdata(shmem_pdev); > + > + return priv->alloc(size, gfp, priv); > +} > + > +void cc_shmem_free(void *addr, size_t size) > +{ > + struct shmem_priv *priv; > + > + if (!shmem_pdev) > + return; > + > + priv = platform_get_drvdata(shmem_pdev); > + > + priv->free(addr, size, priv); > +} > + > +static int intel_shmem_init(struct platform_device *pdev) > +{ > + struct shmem_priv *priv; > + dma_addr_t *handle; > + > + handle = devm_kmalloc(&pdev->dev, sizeof(*handle), GFP_KERNEL); > + if (!handle) > + return -ENOMEM; > + > + priv = platform_get_drvdata(pdev); > + > + priv->data = handle; > + > + return dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(64)); > +} > + > +static void *intel_shmem_alloc(size_t size, gfp_t gfp, struct shmem_priv *priv) > +{ > + dma_addr_t *handle = (dma_addr_t *) priv->data; > + > + return dma_alloc_coherent(&priv->pdev->dev, size, handle, gfp); > +} > + > +static void intel_shmem_free(void *addr, size_t size, struct shmem_priv *priv) > +{ > + dma_addr_t *handle = (dma_addr_t *) priv->data; > + > + return dma_free_coherent(&priv->pdev->dev, size, addr, *handle); > +} > + > +static struct shmem_priv intel_shmem = { > + .init = intel_shmem_init, > + .alloc = intel_shmem_alloc, > + .free = intel_shmem_free, > +};
Hm. What is Intel-specific here. Looks like a generic thing, no?
Maybe just drop all vendor stuff. CC_ATTR_MEM_ENCRYPT should be enough.
-- Kirill A. Shutemov
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