Re: [PATCH 1/1] crypto: ccp - Allocate TEE ring and cmd buffer using DMA APIs

[Tom Lendacky <thomas.lendacky@xxxxxxx>]

On 12/12/22 05:21, Rijo Thomas wrote:
> On 12/10/2022 2:31 AM, Tom Lendacky wrote:
> > On 12/6/22 06:30, Rijo Thomas wrote:
> > > For AMD Secure Processor (ASP) to map and access TEE ring buffer, the
> > > ring buffer address sent by host to ASP must be a real physical
> > > address and the pages must be physically contiguous.
> > >
> > > In a virtualized environment though, when the driver is running in a
> > > guest VM, the pages allocated by __get_free_pages() may not be
> > > contiguous in the host (or machine) physical address space. Guests
> > > will see a guest (or pseudo) physical address and not the actual host
> > > (or machine) physical address. The TEE running on ASP cannot decipher
> > > pseudo physical addresses. It needs host or machine physical address.
> > >
> > > To resolve this problem, use DMA APIs for allocating buffers that must
> > > be shared with TEE. This will ensure that the pages are contiguous in
> > > host (or machine) address space. If the DMA handle is an IOVA,
> > > translate it into a physical address before sending it to ASP.
> > >
> > > This patch also exports two APIs (one for buffer allocation and
> > > another to free the buffer). This API can be used by AMD-TEE driver to
> > > share buffers with TEE.
> > >
> > > Fixes: 33960acccfbd ("crypto: ccp - add TEE support for Raven Ridge")
> > > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Signed-off-by: Rijo Thomas <Rijo-john.Thomas@xxxxxxx>
> > > Co-developed-by: Jeshwanth <JESHWANTHKUMAR.NK@xxxxxxx>
> > > Signed-off-by: Jeshwanth <JESHWANTHKUMAR.NK@xxxxxxx>
> > > Reviewed-by: Devaraj Rangasamy <Devaraj.Rangasamy@xxxxxxx>
> > > ---
> > >    drivers/crypto/ccp/psp-dev.c |   6 +-
> > >    drivers/crypto/ccp/tee-dev.c | 116 ++++++++++++++++++++++-------------
> > >    drivers/crypto/ccp/tee-dev.h |   9 +--
> > >    include/linux/psp-tee.h      |  47 ++++++++++++++
> > >    4 files changed, 127 insertions(+), 51 deletions(-)
> > >
> > > diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
> > > index c9c741ac8442..2b86158d7435 100644
> > > --- a/drivers/crypto/ccp/psp-dev.c
> > > +++ b/drivers/crypto/ccp/psp-dev.c
> > > @@ -161,13 +161,13 @@ int psp_dev_init(struct sp_device *sp)
> > >            goto e_err;
> > >        }
> > >    +    if (sp->set_psp_master_device)
> > > +        sp->set_psp_master_device(sp);
> > > +
> >
> > This worries me a bit...  if psp_init() fails, it may still be referenced as the master device. What's the reason for moving it?
>
> Hmm. Okay, I see your point.
>
> In psp_tee_alloc_dmabuf(), we call psp_get_master_device(). Without above change, psp_get_master_device() returns NULL.
>
> I think in psp_dev_init(), we can add below error handling:
>
> ret = psp_init(psp);
>          if (ret)
>                  goto e_init;
>       ...
>
> e_init:
>      if (sp->clear_psp_master_device)
>          sp->clear_psp_master_device(sp);
>
> Will this help address your concern?

Yes, that works.

> > >        ret = psp_init(psp);
> > >        if (ret)
> > >            goto e_irq;
> > >    -    if (sp->set_psp_master_device)
> > > -        sp->set_psp_master_device(sp);
> > > -
> > >        /* Enable interrupt */
> > >        iowrite32(-1, psp->io_regs + psp->vdata->inten_reg);
> > >    diff --git a/drivers/crypto/ccp/tee-dev.c b/drivers/crypto/ccp/tee-dev.c
> > > index 5c9d47f3be37..1631d9851e54 100644
> > > --- a/drivers/crypto/ccp/tee-dev.c
> > > +++ b/drivers/crypto/ccp/tee-dev.c
> > > @@ -12,8 +12,9 @@
> > >    #include <linux/mutex.h>
> > >    #include <linux/delay.h>
> > >    #include <linux/slab.h>
> > > +#include <linux/dma-direct.h>
> > > +#include <linux/iommu.h>
> > >    #include <linux/gfp.h>
> > > -#include <linux/psp-sev.h>
> > >    #include <linux/psp-tee.h>
> > >      #include "psp-dev.h"
> > > @@ -21,25 +22,64 @@
> > >      static bool psp_dead;
> > >    +struct dma_buffer *psp_tee_alloc_dmabuf(unsigned long size, gfp_t gfp)
> >
> > It looks like both calls to this use the same gfp_t values, you can probably eliminate from the call and just specify them in here.
>
> Okay, I will remove gfp_t flag from the function argument.
>
> > > +{
> > > +    struct psp_device *psp = psp_get_master_device();
> > > +    struct dma_buffer *dma_buf;
> > > +    struct iommu_domain *dom;
> > > +
> > > +    if (!psp || !size)
> > > +        return NULL;
> > > +
> > > +    dma_buf = kzalloc(sizeof(*dma_buf), GFP_KERNEL);
> > > +    if (!dma_buf)
> > > +        return NULL;
> > > +
> > > +    dma_buf->vaddr = dma_alloc_coherent(psp->dev, size, &dma_buf->dma, gfp);
> > > +    if (!dma_buf->vaddr || !dma_buf->dma) {
> >
> > I don't think you can have one of these be NULL without both being NULL, but I guess it doesn't hurt to check.
>
> Okay, we will keep both checks for now.
>
> > > +        kfree(dma_buf);
> > > +        return NULL;
> > > +    }
> > > +
> > > +    dma_buf->size = size;
> > > + > +    dom = iommu_get_domain_for_dev(psp->dev);
> > > +    if (dom)
> >
> > You need a nice comment above this all explaining that. I guess you're using the presence of a domain to determine whether you're running on bare-metal vs within a hypervisor? I'm not sure what will happen if the guest ever gets an emulated IOMMU...
>
> Sure we will add a comment.
>
> We are not trying to determive bare-metal vs hypervisor here, but determine whether DMA handle returned by dma_alloc_coherent() is an IOVA or not.
> If the address is an IOVA, we convert IOVA to physical address using iommu_iova_to_phys(). This was our intention.

Ok, but if a VM gets an emulated IOMMU and ends up with an IOVA, that IOVA 
points to a GPA - and if the size is over a page, then you aren't 
guaranteed to have contiguous physical memory.

Probably not a concern at the moment, but not sure about what happens in 
the future.

> > > +        dma_buf->paddr = iommu_iova_to_phys(dom, dma_buf->dma);
> >
> > If you're just looking to get the physical address, why not just to an __pa(dma_buf->vaddr)?
> >
> > Also, paddr might not be the best name, since it isn't always a physical address, but I can't really think of something right now.
>
> We can use __pa(dma_buf->vaddr) only on bare-metal. In hypervisor, __pa(dma_buf->vaddr) gives pseudo-physical address; pseudo-physical address cannot be understood by ASP.
> ASP needs real physical address (aka machine address). Please see commit message.
>
> We chose the name paddr, since it's a (real) physical address that we want to send across to ASP. I am not sure, why you say - it isn't always a physical address.

Then a nice comment above this explaining all that and the fact that when 
there is no IOMMU the DMA address is actually the physical address, would 
be appropriate. A number of years from now, this will raise questions 
without thorough documentation.

Thanks,
Tom

> Thanks,
> Rijo
>
> > Thanks,
> > Tom
> >
> > > +    else
> > > +        dma_buf->paddr = dma_buf->dma;
> > > +
> > > +    return dma_buf;
> > > +}
> > > +EXPORT_SYMBOL(psp_tee_alloc_dmabuf);
> > > +
> > > +void psp_tee_free_dmabuf(struct dma_buffer *dma_buf)
> > > +{
> > > +    struct psp_device *psp = psp_get_master_device();
> > > +
> > > +    if (!psp || !dma_buf)
> > > +        return;
> > > +
> > > +    dma_free_coherent(psp->dev, dma_buf->size,
> > > +              dma_buf->vaddr, dma_buf->dma);
> > > +
> > > +    kfree(dma_buf);
> > > +}
> > > +EXPORT_SYMBOL(psp_tee_free_dmabuf);
> > > +
> > >    static int tee_alloc_ring(struct psp_tee_device *tee, int ring_size)
> > >    {
> > >        struct ring_buf_manager *rb_mgr = &tee->rb_mgr;
> > > -    void *start_addr;
> > >          if (!ring_size)
> > >            return -EINVAL;
> > >    -    /* We need actual physical address instead of DMA address, since
> > > -     * Trusted OS running on AMD Secure Processor will map this region
> > > -     */
> > > -    start_addr = (void *)__get_free_pages(GFP_KERNEL, get_order(ring_size));
> > > -    if (!start_addr)
> > > +    rb_mgr->ring_buf = psp_tee_alloc_dmabuf(ring_size,
> > > +                        GFP_KERNEL | __GFP_ZERO);
> > > +    if (!rb_mgr->ring_buf) {
> > > +        dev_err(tee->dev, "ring allocation failed\n");
> > >            return -ENOMEM;
> > > -
> > > -    memset(start_addr, 0x0, ring_size);
> > > -    rb_mgr->ring_start = start_addr;
> > > -    rb_mgr->ring_size = ring_size;
> > > -    rb_mgr->ring_pa = __psp_pa(start_addr);
> > > +    }
> > >        mutex_init(&rb_mgr->mutex);
> > >          return 0;
> > > @@ -49,15 +89,8 @@ static void tee_free_ring(struct psp_tee_device *tee)
> > >    {
> > >        struct ring_buf_manager *rb_mgr = &tee->rb_mgr;
> > >    -    if (!rb_mgr->ring_start)
> > > -        return;
> > > +    psp_tee_free_dmabuf(rb_mgr->ring_buf);
> > >    -    free_pages((unsigned long)rb_mgr->ring_start,
> > > -           get_order(rb_mgr->ring_size));
> > > -
> > > -    rb_mgr->ring_start = NULL;
> > > -    rb_mgr->ring_size = 0;
> > > -    rb_mgr->ring_pa = 0;
> > >        mutex_destroy(&rb_mgr->mutex);
> > >    }
> > >    @@ -81,35 +114,36 @@ static int tee_wait_cmd_poll(struct psp_tee_device *tee, unsigned int timeout,
> > >        return -ETIMEDOUT;
> > >    }
> > >    -static
> > > -struct tee_init_ring_cmd *tee_alloc_cmd_buffer(struct psp_tee_device *tee)
> > > +struct dma_buffer *tee_alloc_cmd_buffer(struct psp_tee_device *tee)
> > >    {
> > >        struct tee_init_ring_cmd *cmd;
> > > +    struct dma_buffer *cmd_buffer;
> > >    -    cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
> > > -    if (!cmd)
> > > +    cmd_buffer = psp_tee_alloc_dmabuf(sizeof(*cmd),
> > > +                      GFP_KERNEL | __GFP_ZERO);
> > > +    if (!cmd_buffer)
> > >            return NULL;
> > >    -    cmd->hi_addr = upper_32_bits(tee->rb_mgr.ring_pa);
> > > -    cmd->low_addr = lower_32_bits(tee->rb_mgr.ring_pa);
> > > -    cmd->size = tee->rb_mgr.ring_size;
> > > +    cmd = (struct tee_init_ring_cmd *)cmd_buffer->vaddr;
> > > +    cmd->hi_addr = upper_32_bits(tee->rb_mgr.ring_buf->paddr);
> > > +    cmd->low_addr = lower_32_bits(tee->rb_mgr.ring_buf->paddr);
> > > +    cmd->size = tee->rb_mgr.ring_buf->size;
> > >          dev_dbg(tee->dev, "tee: ring address: high = 0x%x low = 0x%x size = %u\n",
> > >            cmd->hi_addr, cmd->low_addr, cmd->size);
> > >    -    return cmd;
> > > +    return cmd_buffer;
> > >    }
> > >    -static inline void tee_free_cmd_buffer(struct tee_init_ring_cmd *cmd)
> > > +static inline void tee_free_cmd_buffer(struct dma_buffer *cmd_buffer)
> > >    {
> > > -    kfree(cmd);
> > > +    psp_tee_free_dmabuf(cmd_buffer);
> > >    }
> > >      static int tee_init_ring(struct psp_tee_device *tee)
> > >    {
> > >        int ring_size = MAX_RING_BUFFER_ENTRIES * sizeof(struct tee_ring_cmd);
> > > -    struct tee_init_ring_cmd *cmd;
> > > -    phys_addr_t cmd_buffer;
> > > +    struct dma_buffer *cmd_buffer;
> > >        unsigned int reg;
> > >        int ret;
> > >    @@ -123,21 +157,19 @@ static int tee_init_ring(struct psp_tee_device *tee)
> > >          tee->rb_mgr.wptr = 0;
> > >    -    cmd = tee_alloc_cmd_buffer(tee);
> > > -    if (!cmd) {
> > > +    cmd_buffer = tee_alloc_cmd_buffer(tee);
> > > +    if (!cmd_buffer) {
> > >            tee_free_ring(tee);
> > >            return -ENOMEM;
> > >        }
> > >    -    cmd_buffer = __psp_pa((void *)cmd);
> > > -
> > >        /* Send command buffer details to Trusted OS by writing to
> > >         * CPU-PSP message registers
> > >         */
> > >    -    iowrite32(lower_32_bits(cmd_buffer),
> > > +    iowrite32(lower_32_bits(cmd_buffer->paddr),
> > >              tee->io_regs + tee->vdata->cmdbuff_addr_lo_reg);
> > > -    iowrite32(upper_32_bits(cmd_buffer),
> > > +    iowrite32(upper_32_bits(cmd_buffer->paddr),
> > >              tee->io_regs + tee->vdata->cmdbuff_addr_hi_reg);
> > >        iowrite32(TEE_RING_INIT_CMD,
> > >              tee->io_regs + tee->vdata->cmdresp_reg);
> > > @@ -157,7 +189,7 @@ static int tee_init_ring(struct psp_tee_device *tee)
> > >        }
> > >      free_buf:
> > > -    tee_free_cmd_buffer(cmd);
> > > +    tee_free_cmd_buffer(cmd_buffer);
> > >          return ret;
> > >    }
> > > @@ -167,7 +199,7 @@ static void tee_destroy_ring(struct psp_tee_device *tee)
> > >        unsigned int reg;
> > >        int ret;
> > >    -    if (!tee->rb_mgr.ring_start)
> > > +    if (!tee->rb_mgr.ring_buf->vaddr)
> > >            return;
> > >          if (psp_dead)
> > > @@ -256,7 +288,7 @@ static int tee_submit_cmd(struct psp_tee_device *tee, enum tee_cmd_id cmd_id,
> > >        do {
> > >            /* Get pointer to ring buffer command entry */
> > >            cmd = (struct tee_ring_cmd *)
> > > -            (tee->rb_mgr.ring_start + tee->rb_mgr.wptr);
> > > +            (tee->rb_mgr.ring_buf->vaddr + tee->rb_mgr.wptr);
> > >              rptr = ioread32(tee->io_regs + tee->vdata->ring_rptr_reg);
> > >    @@ -305,7 +337,7 @@ static int tee_submit_cmd(struct psp_tee_device *tee, enum tee_cmd_id cmd_id,
> > >          /* Update local copy of write pointer */
> > >        tee->rb_mgr.wptr += sizeof(struct tee_ring_cmd);
> > > -    if (tee->rb_mgr.wptr >= tee->rb_mgr.ring_size)
> > > +    if (tee->rb_mgr.wptr >= tee->rb_mgr.ring_buf->size)
> > >            tee->rb_mgr.wptr = 0;
> > >          /* Trigger interrupt to Trusted OS */
> > > diff --git a/drivers/crypto/ccp/tee-dev.h b/drivers/crypto/ccp/tee-dev.h
> > > index 49d26158b71e..9238487ee8bf 100644
> > > --- a/drivers/crypto/ccp/tee-dev.h
> > > +++ b/drivers/crypto/ccp/tee-dev.h
> > > @@ -16,6 +16,7 @@
> > >      #include <linux/device.h>
> > >    #include <linux/mutex.h>
> > > +#include <linux/psp-tee.h>
> > >      #define TEE_DEFAULT_TIMEOUT        10
> > >    #define MAX_BUFFER_SIZE            988
> > > @@ -48,17 +49,13 @@ struct tee_init_ring_cmd {
> > >      /**
> > >     * struct ring_buf_manager - Helper structure to manage ring buffer.
> > > - * @ring_start:  starting address of ring buffer
> > > - * @ring_size:   size of ring buffer in bytes
> > > - * @ring_pa:     physical address of ring buffer
> > >     * @wptr:        index to the last written entry in ring buffer
> > > + * @ring_buf:    ring buffer allocated using DMA api
> > >     */
> > >    struct ring_buf_manager {
> > >        struct mutex mutex;    /* synchronizes access to ring buffer */
> > > -    void *ring_start;
> > > -    u32 ring_size;
> > > -    phys_addr_t ring_pa;
> > >        u32 wptr;
> > > +    struct dma_buffer *ring_buf;
> > >    };
> > >      struct psp_tee_device {
> > > diff --git a/include/linux/psp-tee.h b/include/linux/psp-tee.h
> > > index cb0c95d6d76b..c0fa922f24d4 100644
> > > --- a/include/linux/psp-tee.h
> > > +++ b/include/linux/psp-tee.h
> > > @@ -13,6 +13,7 @@
> > >      #include <linux/types.h>
> > >    #include <linux/errno.h>
> > > +#include <linux/dma-mapping.h>
> > >      /* This file defines the Trusted Execution Environment (TEE) interface commands
> > >     * and the API exported by AMD Secure Processor driver to communicate with
> > > @@ -40,6 +41,20 @@ enum tee_cmd_id {
> > >        TEE_CMD_ID_UNMAP_SHARED_MEM,
> > >    };
> > >    +/**
> > > + * struct dma_buffer - Structure for a DMA buffer.
> > > + * @dma:    DMA buffer address
> > > + * @paddr:  Physical address of DMA buffer
> > > + * @vaddr:  CPU virtual address of DMA buffer
> > > + * @size:   Size of DMA buffer in bytes
> > > + */
> > > +struct dma_buffer {
> > > +    dma_addr_t dma;
> > > +    phys_addr_t paddr;
> > > +    void *vaddr;
> > > +    unsigned long size;
> > > +};
> > > +
> > >    #ifdef CONFIG_CRYPTO_DEV_SP_PSP
> > >    /**
> > >     * psp_tee_process_cmd() - Process command in Trusted Execution Environment
> > > @@ -75,6 +90,28 @@ int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
> > >     */
> > >    int psp_check_tee_status(void);
> > >    +/**
> > > + * psp_tee_alloc_dmabuf() - Allocates memory of requested size and flags using
> > > + * dma_alloc_coherent() API.
> > > + *
> > > + * This function can be used to allocate a shared memory region between the
> > > + * host and PSP TEE.
> > > + *
> > > + * Returns:
> > > + * non-NULL   a valid pointer to struct dma_buffer
> > > + * NULL       on failure
> > > + */
> > > +struct dma_buffer *psp_tee_alloc_dmabuf(unsigned long size, gfp_t gfp);
> > > +
> > > +/**
> > > + * psp_tee_free_dmabuf() - Deallocates memory using dma_free_coherent() API.
> > > + *
> > > + * This function can be used to release shared memory region between host
> > > + * and PSP TEE.
> > > + *
> > > + */
> > > +void psp_tee_free_dmabuf(struct dma_buffer *dma_buffer);
> > > +
> > >    #else /* !CONFIG_CRYPTO_DEV_SP_PSP */
> > >      static inline int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf,
> > > @@ -87,5 +124,15 @@ static inline int psp_check_tee_status(void)
> > >    {
> > >        return -ENODEV;
> > >    }
> > > +
> > > +static inline
> > > +struct dma_buffer *psp_tee_alloc_dmabuf(unsigned long size, gfp_t gfp)
> > > +{
> > > +    return NULL;
> > > +}
> > > +
> > > +static inline void psp_tee_free_dmabuf(struct dma_buffer *dma_buffer)
> > > +{
> > > +}
> > >    #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
> > >    #endif /* __PSP_TEE_H_ */